Elsevier Editorial System(tm) for Scientia Horticulturae Manuscript Draft Manuscript Number: Title: Current status of vegetable grafting (Diffusion, grafting techniques, automation) Article Type: Vegetable Grafting Special Issue Section/Category: Vegetable Production Keywords: Vegetable grafting, Cucurbits, Solanum spp., Environmentally-friendly produce, Organic produce, Grafting machine, Grafting robot Corresponding Author: Dr. Jung-Myung Lee, Ph.D. Corresponding Author's Institution: Kyung Hee University First Author: Jung-Myung Lee, Ph. D. Order of Authors: Jung-Myung Lee, Ph. D. ; Jung-Myung Lee, Ph.D.; Chieri Kubota, Ph. D.; S. J. Tao, Ph. D.; Zhilong Bie, Ph. D; Pedro Hoyos Echevarria, Ph. D; Luigi Morra, Ph. D. Suggested Reviewers: Dan Leskovar Ph. D. Professor, Horticulture, Texas A&M University, USA d-leskovar@tamu.edu Transplant Production Specialist Giuseppa Colla Ph. D. Professor, GEMINI, Univ. of Tuscia, Italy giucolla@unitus.it vegetable specialist Yun-Chan Heo Ph. D. Researcher, Plant Genetic Resources, RDA, Korea wmelon@rda.go.kr Vegetable and grafting specialist Yoshiteru Sakata Ph. D. Researcher, AFFRC, Japan ysakata@affrc.go.jp Vegetable seed & transplant specialist Reza Salehi Ph. D. Assistant Professor, Horticulture, Univ. of Teheran, Iran salehir@ut.ac.ir grafting & vegetable crop specialist Menahem Edelstein Ph. D. Researcher, Vegetable, Volcani Agric Institute, Israel medelst@volcani.agri.gov.il

vegetable grafting specialist

Cover Letter from JMLee, Korea for an article to Special Issue of Vegetable Grafting

Submitted by Jung-Myung Lee

Republic of Korea

E mail: jmlee@khu.ac.kr

Current status of vegetable grafting

(Diffusion, grafting techniques, automation)

Jung-Myung Lee a,*

, C. Kubota b, S.J. Tsao

c, Z. Bie

d, P. Hoyos Echevarria

e, L. Morra

f, M. Oda

g

a Honorary Professor, Department of Horticultural Biotechnology, Kyung Hee University, Republic of Korea b School of Plant Science, Univ. of Arizona, USA c Dept. of Horticulture, Natl’ Taiwan Univ., Taiwan d College of Horticulture and Forestry, Huazhong Agric. Univ., China e Polytech University of Madrid, Spain

f Cra-Unita di ricerca, per le colture alternative al tobacco, Italy g Osaka Pref. University., Japan

-

________________________________________________________________________________________________________________

__________

*,1 Corresponding author at : Department of Horticultural Biotechnology, College of Life Sciences, Global Campus of Kyung Hee

University, Republic of Korea 446-701, Tel: +82-31-201-2618, Fax: +82-31-202-1740, Email: jmlee@khu.ac.kr

Abstract:

Vegetable production by using grafted seedlings, which originated in Asia particularly in Japan and Korea to

avoid the serious crop loss caused by infection of soil-borne diseases aggravated by successive cropping, is now

rapidly spreading over the world. Vegetable grafting has been safely adapted for the production of organic as

well as environmentally-friendly produces which are the major concern in recent years as means of minimizing

uptake of undesirable agrochemical residues in fresh vegetables. The number as well as the size of commercial

vegetable seedling producers has markedly increased in concomitant with the increases in farmers’ preferences

on grafted seedlings of high quality and better performance. In addition to the widely recognized advantages of

disease tolerance and high crop yields, this technology is also highly effective in ameliorating crop losses

caused by adverse environmental conditions such as low soil temperature and high soil salts, especially under

protected cultivations where successive cropping or continuous farming is routinely practiced. Grafted

seedlings are much favored in hydroponics farming systems where the chances of rapid spread of noxious

diseases, once infected, is expected to be phenomenal. Active research has been focused to develop efficient

rootstocks and handy grafting tools. In addition, researchers are eager to develop grafting machines or robots to

reduce the higher price of grafted seedlings for more general use and transplanting machines of the grafted

seedlings. The quality of grafted transplants is extremely important for the successful farming in many cases in

addition to different cultivation techniques for the grafted plants to maximize high-quality crop yield. Use of

grafted vegetables has been and will be markedly increased in concomitant with the increased use of improved

soil mix or substrate, farmer’s preferences for better seedlings, efficient management of nursery system, lower

prices of the grafted seedlings, and efficient nationwide delivery and/or transportation system. Improved

grafting methods to cut down the labor cost for grafting and subsequent handling of plug-grown grafted

transplants will contribute further for the increased use of grafted vegetables worldwide.

Keywords: Vegetable grafting, Cucurbits, Solanum spp., Environmentally-friendly produce, Organic produce,

Grafting machine, Grafting robot

Cover Letter

1

Current status of vegetable grafting 1

(Diffusion, grafting techniques, automation) 2 3

Jung-Myung Lee a,*

, C. Kubota b, S.J. Tsao

c, Z. Bie

d, P. Hoyos Echevarria

e, L. Morra

f, M. Oda

g 4

a Honorary Professor, Department of Horticultural Biotechnology, Kyung Hee University, Republic of Korea 5 b School of Plant Science, Univ. of Arizona, USA 6 c Dept. of Horticulture, Natl’ Taiwan Univ., Taiwan 7 d College of Horticulture and Forestry, Huazhong Agric. Univ., China 8 e Polytech University of Madrid, Spain 9 f Cra-Unita di ricerca, per le colture alternative al tobacco, Italy 10 g Osaka Pref. University., Japan 11 _____________________________________________________________________________________________________________ 12 *,1 Corresponding author at : Department of Horticultural Biotechnology, College of Life Sciences, Global Campus of Kyung Hee 13 University, Republic of Korea 446-701, Tel: +82-31-201-2618, Fax: +82-31-202-1740, Email: jmlee@khu.ac.kr 14

15

Abstract: 16

Vegetable production by using grafted seedlings, which originated in Asia particularly in Japan and Korea to 17

avoid the serious crop loss caused by infection of soil-borne diseases aggravated by successive cropping, is now 18

rapidly spreading over the world. Vegetable grafting has been safely adapted for the production of organic as 19

well as environmentally-friendly produces which are the major concern in recent years as means of minimizing 20

uptake of undesirable agrochemical residues in fresh vegetables. The number as well as the size of commercial 21

vegetable seedling producers has markedly increased in concomitant with the increases in farmers‟ preferences 22

on grafted seedlings of high quality and better performance. In addition to the widely recognized advantages of 23

disease tolerance and high crop yields, this technology is also highly effective in ameliorating crop losses 24

caused by adverse environmental conditions such as low soil temperature and high soil salts, especially under 25

protected cultivations where successive cropping or continuous farming is routinely practiced. Grafted 26

seedlings are much favored in hydroponics farming systems where the chances of rapid spread of noxious 27

diseases, once infected, is expected to be phenomenal. Active research has been focused to develop efficient 28

rootstocks and handy grafting tools. In addition, researchers are eager to develop grafting machines or robots to 29

reduce the higher price of grafted seedlings for more general use and transplanting machines of the grafted 30

seedlings. The quality of grafted transplants is extremely important for the successful farming in many cases in 31

addition to different cultivation techniques for the grafted plants to maximize high-quality crop yield. Use of 32

grafted vegetables has been and will be markedly increased in concomitant with the increased use of improved 33

soil mix or substrate, farmer‟s preferences for better seedlings, efficient management of nursery system, lower 34

prices of the grafted seedlings, and efficient nationwide delivery and/or transportation system. Improved 35

Editted manuscriptClick here to view linked References

2

grafting methods to cut down the labor cost for grafting and subsequent handling of plug-grown grafted 36

transplants will contribute further for the increased use of grafted vegetables worldwide. 37

Keywords: Vegetable grafting, Cucurbits, Solanum spp., Environmentally-friendly produce, Organic produce, 38

Grafting machine, Grafting robot 39

40

1. Introduction 41

42

Even though grafting has been practiced in fruit trees for thousands of years (Ashita, 1927; Sakata et al., 43

2007), vegetable grafting has been only recently widely adapted. Old records on vegetable grafting can be 44

found in Chinese as well as in Korean and Japanese writings. The commercial use of vegetable grafting is a 45

relatively recent innovation. The invention of plastic films and active uses for the production of vegetables in 46

the late 1950s provided the momentum for generalized production and use of grafted vegetables. The early use 47

of grafted vegetables was associated with protected cultivation which involved successive cropping. 48

Commercial vegetable grafting, originated in Japan and Korea and practiced for about 30 years until 1990, was 49

introduced to the Western countries from the early 1990s and is currently being globally practiced using local 50

scion cultivars and introduced rootstocks. Fortunately, seed companies have been able to select and/or breed 51

well-adapted scion cultivars for intensive growing. Even though the benefits of using grafted seedlings are 52

widely recognized, many other factors should be carefully considered to ensure successful cultivation and 53

satisfactory income with this new technology. For example, generous use of chemical fertilizers and synthetic 54

pesticides should be minimized for the production of environmentally-friendly produces, in which interest has 55

been exploding in recent years (Cushman and Huan, 2008; Davis et al., 2008; Kubota et al., 2008; Lee and Oda, 56

2003; Sakata et al., 2007). It has been well-known that the use of proper rootstocks can minimize the problems 57

associated with successive cropping and stress tolerance (Hoyos Echeverria, 2010; Lee, 1994; Lee et al., 1998, 58

Lee, 2003). The increasing awareness and interest in fresh horticultural produce has rapidly expanded among 59

people of all ages and locations to look for safe, environmentally-friendly, and functional foods. Fast foods are 60

now regarded as dangerous in many developed countries and obesity is currently defined as a disease, rather 61

than a symbol of health and prosperity. Many Asian people have been consuming more horticultural crops as 62

compared to those living in western countries, especially vegetables. However, because of the very limited total 63

and per capita cultivation area, intensive use of the land is inevitable to secure food and earnings for the 64

3

majority of farmers. Intensive land use is most frequently performed by multiple or successive cropping even in 65

Temperate Zone areas (Lee et al., 2008). In the southern parts of Korea, it is not unusual to find watermelon 66

growers producing 3 to 4 crops a year in the same greenhouse. The farmers usually apply heavy amount of 67

chemical fertilizers and frequent pesticides treatment to the densely-planted vines to obtain high crop yield and 68

earnings. Since the plants are cultivated under the protected structures year-round except for several months 69

from May to September, the plants are frequently subjected to poor to extreme environmental conditions in the 70

high tunnels during off- season cultivation (Lee, 2008). As a result farmers frequently encounter various 71

problems caused by successive as well as off-season cropping such as heavy infection of soil-borne diseases, 72

low temperatures during the winter, high humidity in the high tunnels, insufficient light intensity, and lack of 73

well-balanced fertilization. The plants and the fruits grown under these stressful conditions frequently suffer 74

from heavy incidence of soil-borne diseases, suboptimal temperature stresses, various physiological disorders, 75

and quality deterioration. 76

77

2. Purpose of vegetable grafting 78

79

2.1. Tolerance to soil-borne diseases 80

81

The vigorous roots of the rootstock exhibit excellent tolerance to serious soil-borne diseases, such as those 82

caused by Fusarium, Verticillium, Phytophthora, Pseudomonas, and viruses, even though the degree of 83

tolerance varies considerably with the rootstocks. The mechanism of disease resistance, however, has not been 84

intensively investigated. These characteristics are crucial for the plants grown under protected environments, 85

where extended harvesting and higher crop yield are expected. Resistant rootstocks can also effectively 86

counteract the rapid disease spread when the plants are grown in hydroponics system. The disease tolerance in 87

grafted seedlings may be entirely due to the tolerance of rootstock roots to such diseases (Table 1). However, in 88

actual planting, adventitious rooting from the scion is common (Fig. 1). Plants having the root systems of the 89

scion and rootstock are expected to be easily infected by soil-borne diseases. However, seedlings having dual 90

root systems occasionally exhibit a certain degree of disease resistance, thus partially supporting the previous 91

report that substances associated with Fusarium tolerance are synthesized in the root and move to the scion 92

4

through the xylem. On the contrary, it is generally accepted that the disease-susceptible characteristics of the 93

scion are not transported to the rootstock. 94

95

Table 1. Purpose of grafting in vegetables (Heo, 2000; Lee, 1994; Lee et al., 1998; Lee and Oda, 2003). 96

Fig. 1. Adventitious rooting from the melon scion grafted onto squash rootstocks through the hypocotyls cavity 97

of the rootstock, thus counteracting the grafting effect in some cases (A) and rooting from the scion of the TAG-98

grafted cucumber onto figleaf gourd (B). 99

100

2.2. Plant vigor promotion (Reduced fertilizer and agrochemical applications) 101

102

Since the root systems of selected rootstocks are usually much larger and more vigorous, they can absorb 103

water and nutrients much more efficiently as compared to non-grafted plants, in addition to the disease 104

tolerance described above. 105

For example, in watermelons, it is routinely recommended to reduce the amount of chemical fertilizers 106

application to about one-half to two-third as compared to the standard recommendation for the non-grafted 107

plants (Lee and Oda, 2003, Salehi et al., 2009). This is especially true for nitrogen fertilizers during early 108

seedling growth for the safe setting of fruits at the desired node positions for early fruit set. Early fruit set is 109

crucial for the early harvesting in greenhouses to secure good market prices. Otherwise the fruit set as well as 110

the fruit quality at harvest will not be high enough to secure highest market grading. 111

Cytokinin composition in bleeding xylem sap from decapitated plants, grafted or own-rooted, is much 112

different in various cucurbits and, more interestingly, the scion portion is capable of converting the composition 113

of cytokinins in the ascending xylem sap (Table 2) in relative short period, thus clearly indicating the 114

contribution of higher cytokinin concentration in the ascending xylem sap for the growth promotion of grafted 115

scion. 116

The frequency of agrochemical application also can be significantly reduced by using vigorous rootstocks. 117

Spray of fungicides may also be greatly reduced or totally excluded depending upon the diseases, thus greatly 118

enhancing the successful production of organically-grown fruits. It has been shown that the incidence of various 119

diseases in tomatoes can be easily minimized by using disease tolerant rootstocks rather than using pesticides. 120

Even the scion infection of certain virus diseases (TMV races) could be markedly influenced. Expression of 121

deficiency symptoms may be minimized with proper rootstocks. Wise selection of rootstocks can also 122

5

effectively replace methyl bromide. In cucumber, vigorous root system of the rootstock can effectively absorb 123

water so that less frequent irrigation may be practiced. 124

125

Table 2. Cytokinin composition in xylem sap collected from intact and grafted plants of cucumber, squash, and 126

figleaf gourd plants. 127

128

2.3. Yield increases 129

130

Grafting is associated with noticeable increases in fruit yield in many fruiting vegetables regardless of 131

infection with certain soil-borne diseases. In oriental melons, fresh fruit weight increases of 25~55% have been 132

reported as compared to own-rooted plants. These yield increases were closely correlated with the maintenance 133

of good plant vigor until late in the growing season in addition to disease resistance. Virtually no marketable 134

yield was obtained from plants heavily infected with Fusarium. Similar results were obtained with tomato. Up 135

to 54% increase in marketable yield was obtained with „Kagemusia‟ and 51% with „Helper‟ rootstocks (Chung 136

and Lee, 2007). There were also significant decreases in abnormal fruits in plant grafted onto most rootstocks 137

as compared with the own-rooted „Seokwang‟ tomato. Similar yield increases have been reported by other 138

researchers on watermelon, cucumber (Lee and Oda, 2003), melon, pepper, and eggplant. 139

140

2.4. Tolerances to adverse soil temperature and moisture conditions 141

142

Tolerance to extreme temperature is crucial for the production of fruiting vegetables under the winter 143

greenhouse conditions. In cucurbits, cropping area under protected structure is substantially larger than field 144

cultivation for watermelon, cucumber, and melon in Korea. The transplanting of seedlings for protected 145

cultivation is usually done in early to mid-winter and fruit harvesting is usually finished by spring to early 146

summer. Even though many growers heat their greenhouse during the winter, there are more growers who do 147

not have electric or gas-generated heating systems and depend solely on preservation of solar energy capture 148

during the daytime. These growers find it difficult to maintain optimum temperatures in winter greenhouses, 149

especially soil temperatures which are far below the optimum thus causing transplanted plants to suffer during 150

the early stages of cultivation. This is especially true with crops that require high temperatures for optimum 151

performance such as watermelon and oriental melon. Grafting watermelon, melon, cucumber, even summer 152

6

squash onto low-temperature tolerant rootstocks such as interspecific hybrid between Cucurbita maxima x C. 153

moschata or figleaf gourd can greatly reduce the risk of severe growth inhibition caused by low soil 154

temperatures in winter greenhouses. Cucumber grafted onto figleaf gourd (Cucurbita ficifolia), an excellent 155

grower even at low soil temperature, grows much faster than own-rooted cucumber or even summer squash 156

because of the rootstock‟s ability to absorb water and nutrient more efficiently at low temperatures (Tachibana, 157

1982). Many physiological disorders can be effectively minimized by using grafted plants. Since the 158

resistance to temperature stresses varies with the rootstocks, different rootstocks should be used during the hot 159

summer season. 160

161

2.5. Effect of fruit quality 162

163

The fruit size of watermelons grafted to rootstock having vigorous root systems is often significantly 164

increased compared to the fruit from intact plants, and many growers practice grafting mainly for this reason. It 165

is also known that other quality characteristics, such as fruit shape and skin color, rind thickness, and soluble 166

solids concentrations are influenced by rootstock. In cucumbers, especially those for export, external color and 167

bloom development are important quality factors. Even though these are usually regarded as cultivar-specific 168

hereditary characteristics, they can be greatly influenced by the rootstock. However, the effects of rootstocks on 169

some fruit quality are often detrimental, except for increasing fruit size, shape, and bloomless-fruit production 170

in cucumber. Therefore, most newly-devised growing recommendations are aimed at minimizing the 171

detrimental effects of rootstock on fruit quality (Cushman and Huan, 2008; Ko, 2008) 172

173

2.6. Others-Physiology, Peculiarity, Hobby, and Education 174

175

Grafting can be demonstrated for various other reasons. For example, tomatoes, eggplants, pepinos can be 176

grafted on potatoes so that four or more different kind of vegetables could be harvested from a plant. Chinese 177

cabbages and cabbages may be grafted on top of radish with radish roots. Grafting can be made for some 178

physiological studies such as flower induction and early flowering. Grafting is also commonly used for 179

bioassays of virus infection. Use of grafted plants is highly recommended for hydroponics to avoid rapid spread 180

of root disease within the system (Lee and Oda, 2003; Davis et al., 2008). 181

182

7

2.7. Rootstocks 183

184

Various rootstocks have been screened from the existing cultivars for use in each crop. Recently, however, 185

seed companies and various breeders are eager to breed superior rootstocks for vegetables grown under certain 186

conditions and environments. The growers, therefore, have to make decision on selection of rootstocks most 187

suitable for their specific requirements. Some of the characteristics in cucurbits are summarized in Tables 3-6. 188

Cucurbit species and number of registered rootstock cultivars are rapidly increasing due mostly to the increased 189

cultivation of grafted plants under various cultural as well as environmental conditions (Kato and Lou, 1989; 190

Ko, 1999; Lee et al., 2008). In general, grafting is more commonly practiced for vegetables grown under 191

protected environment as compared to those under the field condition. Rootstocks belonging to different species 192

are preferred because the response to biological and environmental stresses differs considerably depending 193

upon the rootstock and cultivar species in cucurbits (Table 5) as well as in solanaceous crops (Table 6). 194

195

Table 3. Rootstocks for cucurbitaceous crops and some related characteristics (Lee and Oda, 2003). 196

Table 4. Rootstock species and number of registered rootstock cultivars for cucurbitaceous crops in China (Bie, 197

2010, Personal communication). 198

Table 5. Response of cucurbits to biological and environmental stresses (Ko, 1999). 199

Table 6. Rootstocks for solanaceous crops (Lycopersicon, Solanum, Capsicum, and Datura) and their 200

performances (Lee and Oda, 2003). 201

202

3. Current status 203

204

3.1. Production 205

206

Although the possibility and benefits of using grafted plants were recognized much earlier, large-scale 207

commercial growing of grafted vegetables can be traced from the late 1950s to the early 1960s in Japan and 208

Korea. Statistics on the current use of grafted plants in Korea and Japan is shown in Table 7. In cucurbitaceous 209

crops, over 90% of watermelon seedlings are grafted onto various rootstocks and about 75% of cucumbers in 210

both countries. Melons show variable grafting percentages depending upon the genotypes. For example, 211

8

virtually all the oriental melons (Cucumis sativus var. makuwa MAKINO) are grafted onto squash in Korea, but 212

other melons are selectively grafted depending on the genotypes using various rootstocks (Ko 1999, 2008). In 213

solanaceous vegetables, 20~40% of tomatoes are grafting, 20~40% of eggplants, and 5~10% of capsicum 214

peppers. Since grafting is mostly practiced in cucurbits and solanaceous vegetables, the percentages of 215

grafting in all vegetables was only about 5% in 2007. More than 700 million grafted seedlings were estimated 216

to be produced in 2008 in Korea as well as in Japan (Table 7). 217

Even though vegetable grafting is actively practiced in other countries (Tables 8 and 9), accurate statistics are 218

unavailable. However, 40 to 45 million grafted seedlings were distributed in North America in 2005, about 30 219

million in Spain (Hoyos Echevarria, 2010, personal communication), 25 million in Italy (Morra and Billoto, 220

2008), 60 million in Honduras, etc. It was estimated that about 20% of China‟s watermelons and cucumbers are 221

grafted (Bie, 2010, personal communication). Rapid increases in the use of grafted seedlings are expected 222

throughout the world for some decades (Davis et al.,2008; Lee 2003; Lee 2007; Lee and Oda 2003; Oda 2007). 223

Well known multinational seed companies are now supplying the rootstock seeds which virtually have little or 224

negative effects on fruit quality. Even though cucurbits (watermelon, melons, and cucumbers) and solanaceous 225

crops (tomatoes, eggplants, capsicum peppers) are routinely grafted, many other vegetables can be grafted for 226

other purposes (Lee and Oda, 2003). 227

228

Table 7. Vegetable cultivation area, number of total seedlings, and number of grafted seedlings needed in Korea 229

and Japan. Approximate 40 million grafted seedlings are estimated to be used in North American greenhouses 230

(Kubota, 2008). 231

Table 8. Current status of the estimated use of grafted vegetables in Asian and other countries and regions as of 232

April 30, 2010. 233

Table 9. Current status of the estimated use of grafted vegetables in European and other countries as of April 30, 234

2010. 235

236

The majority of the grafted seedlings are produced by commercial growers globally. In Korea, more than 200 237

seedlings growers, excluding individual farmers and farmers‟ associations, are producing plug seedlings and 238

about half of them are producing grafted seedlings. Hoban Nursery, the largest one in Korea located in 239

Chooncheon, Gangweon-do, produced 15.6 million grafted seedlings in 2007 (Table 10, Fig. 2). Nongwoo 240

GreenTek produced 9.0 million followed by Nosung, Gongju, and Yeoju. Pureun Nursery produced about 2.8 241

9

million seedlings, mostly for export. Yet, less than 10% of all grafted seedlings are estimated to be produced by 242

commercial growers in Korea (Ko, 2008). The price of grafted seedlings varies with crops and countries, 243

0.8~1.2 $ in the USA and some Asian countries including Japan and Korea, and 0.6~1.0 euros in Spain and 244

some European countries (Table 9). The price of scion seeds, rootstock seeds, and labor cost for grafting and 245

postgraft care are considered to be the major factors in price determination. In Shandong Province in China, 246

over 200 commercial growers are currently producing grafted vegetables and the biggest one produced 20 247

million grafted seedlings in 2009 (Bie, 2010, personal communication). 248

249

Table 10. Number of grafted seedlings produced by some major nurseries in Korea in 2008 (unit: thousand). 250

Fig. 2. Hand grafting of high quality tomato seedlings at Hoban Nursery, Gangwon-do, Korea. 251

252

3.2. International Export 253

254

Even though plants growing in pot soil are frequently rejected at customs because of strict quarantine 255

regulations, grafted seedlings produced by export-oriented nurseries easily pass through the regulation. One of 256

the reasons for this easy pass is the use of sterile substrates rather than contaminated soils. Furthermore the 257

growing period is very short, usually less than 30 days in most cases except eggplants. Transportation and 258

shipping are also easy with plug seedlings grown in cell trays. Tomatoes are the major grafted vegetable for 259

export, followed by watermelons and eggplants. It is worthwhile to note that seedling growers in Agadir, 260

Morocco exported 12 million grafted seedlings to southern Europe countries in 2007 and it is expected that this 261

kind of export will be markedly increased in coming years (Fig. 3). In North America, Canada is the major 262

source of grafted seedlings, exporting more than 10 million grafted plants to the USA and northern Mexico. 263

Active export of grafted transplant from Korea to Japan had been taken place for several years via several 264

nurseries. 265

266

Fig. 3. Plug seedlings grown in Morocco for export to southern European countries. 267

268

4. Grafting methods and acclimatization 269

270

10

Graftage is a process that involves: (1) the choice of rootstock and scion species, (2) creation of a graft union 271

by physical manipulation, (3) healing of the union, and (4) acclimation of the compound plant. In fruit species, 272

pruning is often an essential part of the grafting process. Grafting methods vary greatly and considerably 273

depending upon the kind of crops, farmers‟ experiences and preferences, facilities and machines available, 274

numbers of grafting, and even by the purpose of grafting such as grafting for their own uses or for sales only by 275

commercial growers. In case of Japan (Table 11), hole insertion grafting is by far the most popular grafting 276

method in watermelon. However, in cucumbers, tongue insertion grafting is most popular among the individual 277

growers producing transplants for their own use. In contrast, the commercial growers prefer splice grafting. In 278

eggplant, individual farmers prefer split grafting where as the commercial growers definitely prefer splice 279

grafting. In summary, less experienced, small-scale farmers select tongue approach grafting for most vegetables 280

whereas large-scaled experienced professional seedling producers like to adapt splice grafting. It is generally 281

accepted that the quality of seedlings grafted by splice grafting is much better than those grafted by tongue 282

approach grafting. Manual or hand grafting is by far the major grafting method even though several grafting 283

machines and semi-automatic machines or robots have been developed and commercially available. 284

285

Table 11. Grafted seedlings produced by different grafting methods in Japan (revised from the survey data of 286

Yoshioka, 2001). 287

288

4.1. Manual or Hand Grafting 289

There are a number of grafting methods applicable for herbaceous grafting. Some of the most frequently used 290

methods are diagrammed in Fig. 4. 291

Fig. 4. Major grafting methods in cucurbits and solanaceous vegetables. 292

Hole insertion grafting (HIG). 293

Grafting methods vary with the kind of crops being grafted, preferences and experience of the growers, and 294

the kind of grafting machines or robots available. For watermelons, hole-insertion hypocotyl grafting (Fig. 4A) 295

is favored by many farmers in many areas because of the smaller seedling size of watermelon as compared to 296

the size of the rootstock, which is usually squash or bottle gourd. Watermelon seeds are sown 7 to 8 days after 297

11

the sowing of gourd seeds (rootstock) or 3 to 4 days after sowing squash rootstock seeds. Grafting is made 7 to 298

8 days after the sowing of watermelon seeds. Both the scion and rootstock should be uniform and strong 299

enough to undergo the grafting operation. The true leaf including the growing point should be carefully and 300

thoroughly removed and a hole is made with a bamboo or plastic gimlet or drill at a slant angle to the 301

longitudinal direction. The hypocotyl portion of the watermelon is prepared by slant cutting to have tapered end 302

for easy insertion. Care should be given to avoid the insertion into the hypocotyl cavity since this greatly 303

interferes with formation of a rapid union and facilitates later protrusion of watermelon adventitious roots into 304

the soil after downward elongation through the pith cavity of the rootstock (Fig. 1). Some growers insert young 305

watermelon seedlings (usually somewhat etiolated seedlings with cotyledons still in folded position) into the 306

hypocotyl (Fig. 4B). HIG had been favorably practiced for tomato and eggplant for a while, but splice grafting 307

is definitely much favored even among the farmers for their own uses. 308

309

Tongue approach grafting (TAG) 310

311

Tongue approach grafting (Fig. 4C) is usually favored by less experienced farmers and those who do not have 312

a greenhouse with good microclimate control system. Even though this method needs more space and labor as 313

compared to other methods, a higher rate of seedling survival is possible even for beginners. Furthermore, no 314

special facilities and machines are needed for this grafting technique. Since the grafting operation would be 315

much more efficient with both scion and rootstock seedlings having similar height, the seeds of scion (usually 316

watermelons, cucumbers, and melons) are sown 5 to 7 days earlier than the rootstock seeds. The growing point 317

of the rootstocks should be carefully removed before grafting to reduce the unnecessary loss of nutrient for the 318

bud growth and to promote the rapid union of graft interface. Occasionally one cotyledon may also be removed 319

when removing the growing point to ensure complete removal of the growing point and to avoid overcrowding 320

in limited space on the greenhouse bench. The grafting cut for rootstock should be made in a downward 321

direction and the scion cut in an upward direction at an angle, usually 30° to 40° to the perpendicular axis, and 322

deep enough to allow the fusion of as many vascular bundles as possible. After the graft is completed, specially 323

designed clips are placed to fix the graft position. Grafted plants are then planted together in a 9 to 12 cm 324

diameter container. 325

12

The grafted plants are partially shaded for one or two days before placing them under normal greenhouse 326

growing conditions. The lower hypocotyl of the scion of several test plants is cut to examine the degree of 327

graft-take 10 to 12 days after grafting and based upon the results the remaining plants can be handled as 328

described below. The root and lower hypocotyl of the scion are removed from the grafted plant by simply 329

cutting off at the desired position, preferably at the closer position to the grafted position held by the clip. The 330

clips are usually removed at later stages, shortly before transplanting. An experienced person can graft about 331

800 plants per day, but grafting machines and robots specifically designed for this kind of grafting are also 332

available at varying prices. 333

TAG is the oldest and perhaps the most convenient grafting method for herbaceous plants. The method can be 334

used for basically any kind of plants such as cucurbits, solanaceous plants, and many other types. Grafting is 335

performed with very young seedlings and preferably at the hypocotyl portion of the rootstock and scion of 336

cucurbitaceous plants and at the lower epicotyl portion in solanaceous crops. In spite of the simple and easy 337

grafting operation and higher rate of survival, this method is not extensively used by commercial seedling 338

growers mainly because (1) labor required for grafting, (2) labor needed for cutting the rootstock again, (3) 339

needs for removal of clips after union, (4) larger space is needed for growing grafted plants as compared to 340

other methods, and (5) frequent rooting from the scion after transplanting if the seedlings are transplanted too 341

deep (Lee 1994). 342

343

Splice grafting (SG), Tube Grafting (TG), and One Cotyledon Splice Grafting (OC-SG) 344

345

Splice grafting (Fig. 4D, E, J) is very popular among experienced growers and commercial plug seedling 346

nurseries. Splice grafting can be done by hand, machine, or robot and can be applied to most vegetables. The 347

major advantage is the production of strong and healthy grafted seedlings since all the vascular bundles of the 348

scion are fused with those of rootstock and the graft union is strong enough to take all the rough post-graft 349

handling. Intact or excised (root-removed) rootstock seedlings may be used depending upon the growers and 350

farmers‟ preference. For the cucurbit rootstocks, one cotyledon and the growing point are removed for grafting. 351

After placing the scion on the rootstock (Fig. 4D, E), ordinary grafting clips as in tongue approach grafting are 352

used to fix the grafted position tightly together. This is the most common methods for cucurbits and also 353

called as one cotyledon splice grafting (OC-SG). For solanaceous crops, grafting is usually made at lower 354

epicotyl and fixed (Fig. 4J) with ordinary clips, elastic tube-shaped clip with side slit, or ceramic pins (see Pin 355

13

Grafting below) developed specifically for this type of grafting. Tube grafting is performed by holding the 356

grafted position together in a slit elastic tube rather than using the usual grafting clips. The tube may be used 357

several times depending upon the materials. 358

359

Cleft grafting (CG) 360

361

Cleft grafting (Fig. 4F) in herbaceous plants may be somewhat different from those of woody plants. Usually 362

a portion of the stem is cut longitudinally. The rootstock seedlings are decapitated and longitudinal cut is made 363

in a downward direction, 1 to 1.5 cm long and 3/4 depth of the stem diameter. The scion is pruned to have 1 to 364

3 true leaves and the lower stem is cut to slant angle to make a tapered wedge. After placing the scion into the 365

split made on the rootstock, a clip is placed to hold in position until the union. Various types of grafting clips, 366

differing in material, size, shape, and others, have been developed for cleft grafting. Cleft grafting had been 367

used in cucurbits for a while in several countries, but the use is usually confined to solanaceous crops these 368

days. 369

Pin grafting (PG) 370

371

Pin grafting (Fig. 4H, I) is basically the same as the splice grafting. However, instead of placing grafting clips 372

to hold the grafted position, specially designed pins are used to hold the grafted position in place. The ceramic 373

pin developed by Takii Seed Co. in Japan is about 15 mm long and 0.5 mm in diagonal width of the hexagonal 374

cross section. The pins are made of natural ceramic so it can be left on the plant without any problem. The price 375

of ceramic pin is fairly high so that alternative methods are being sought. Experimental results revealed that 376

bamboo pins, rectangular in cross-sectional shape, could successfully replace the expensive ceramic pins at 377

much lower price. Watermelon seedlings grafted by HIG described above are shown in Fig. 5 and a 378

solanaceous grafted plant near maturity is shown in Fig. 6. 379

380

Fig. 5. HIG grafted watermelon seedlings ready for transplanting. 381

Fig. 6. Shape of grafted plant near harvest time (tomato on potato). 382

383

14

4.2. Tools, clips, and grafting aids 384

385

A number of grafting tools to perform automated grafting and to hold the graft union together have been 386

developed by various agricultural companies (Lee and Oda, 2003). Unfortunately, however, most of them have 387

not been widely used by the commercial growers. Simple grafting aids, such as grafting clips, tubes, tapes, and 388

pins have been selectively but widely used for grafting (Fig. 7). The ordinary grafting clips consisting of a 389

round spring made out of plastic (Fig. 7A), have been most extensively used for tongue approach grafting in 390

cucurbits and other crops. The clips, although slightly different in size and shape depending upon manufacturer, 391

are inexpensive, ease to operate and handle for various stem sizes, and can be used many times. Various other 392

clips, especially elastic tube-shaped clips with or without attachment for supporting pole for the grafted 393

seedlings (Fig. 7), are also widely used by many commercial growers for manual grafting as well as for 394

machine or robot grafting. Much smaller elastic slit-tubes are being used in many countries including Israel and 395

The Netherlands (Fig. 7E) for tomato and pepper grafting. Ceramic pin is a very handy and efficient aid to fix 396

the grafted interface, and highly suitable for machine or robot grafting. It can be used with naked hands, with 397

simple pencil-shaped device, or with machine or robots. Adhesive tape or glue, or sometimes aluminum foil, is 398

another means of holding the grafted counterparts in place. Specially designed knives and gimlets for grafting 399

have been manufactured and are used by growers in different parts of the world. A special knife with self-400

feeding connection of skimmed milk or alcohol to inactivate some potent viruses has been developed in The 401

Netherlands and in Korea. A hand held grafting device constructed with changeable stainless steel, single-edge 402

razor blades, makes it possible to simultaneously create a uniform wedge and a receptacle in the stem of 403

Phaseolus vulgaris. Rapid changes have been taking place recently and it is evident that marked progress will 404

be made on these devices with the improvement of grafting technology and introduction of new and efficient 405

grafting robots. Uniformly small seedlings are definitely favored for grafting, especially for machine grafting, 406

so that experienced growers are eager to produce uniform healthy seedlings for efficient grafting by using better 407

quality seeds preferably primed seeds. 408

Fig. 7. Grafting clips and other aids. 409

For tomato, a combination of high humidity and weak light, slightly higher than the light compensation point, 410

prevents wilting of grafted tomato scions and promotes healing of the cut surfaces of grafts. Films reducing 411

15

thermal radiation on acclimatization tunnels depress the rise of leaf temperate and increase the favorable range 412

of light intensity for graft healing. Under these high light intensity and high humidity conditions, healing of the 413

graft union is accelerated by air movement. Several types of acclimatization chambers have been developed and 414

widely used by commercial plug seedling growers in Japan and Korea (Lee and Oda, 2003). 415

416

4.3. Grafting Machines and Robots 417

418

The first robot, the “One Cotyledon Splice Grafting” system was developed in 1980s by IAM BRAIN in 419

Japan to graft cucurbit vegetables (similar to the latest Korean version shown in Fig. 8). The robot took into 420

account variation of seedling shape, location of cutting and gripping, cutting, and attachment. Seedlings were 421

cut at the point of attachment of the cotyledon to the hypocotyl at an angle of 20 ~ 30 for the scion and the 422

rootstock, respectively. The prototype grafting robot was constructed in 1987 and the second in 1989 (Ito, 1992; 423

Kubota et al., 2008). It took 4.5 seconds to make a grafted plant with 95% survival. The demonstration model 424

robot was deemed practical and the results were transferred an agricultural machinery company that developed 425

machines for the market. Prototype semi-automatic grafting system was also developed in Korea. Several 426

grafting robots have been manufactured by the Rural Development Administration (RDA), Korea, and will be 427

distributed to the commercial plug seedling growers at relatively reasonable prices. Three grafting robots have 428

been developed in Korea, two in 1998 and one in 1999, and one was commercialized in 2001. The pin-grafting 429

robot developed by Rural Development Administration for solanaceous crops can graft 1,200 seedlings per 430

hour. The simple and economic grafting machine was developed by Yupoong and has been very popular in 431

Korea. This machine by Yupoong, priced about US $400, has been exported for more than 10 years to many 432

Asian countries and some European countries. This machine can graft up to 600 seedlings per hour by tongue 433

approach grafting, mostly in cucurbitaceous crop. However, an experienced operator is needed to run this 434

machine effectively and efficiently. Recently a multiuse semi-automatic grafting machine has been developed 435

by a private company in Korea (Helper RoboTech) and many growers purchased this machine to graft tomato 436

and pepper plug seedlings. This machine (Fig. 8) has also been actively exported to many foreign countries in 437

recent years because of the reasonable price, multiple functions (can be used for both cucurbit and solanaceous 438

crops), and convenient handling. More recently, a fully-automated grafting robot (1000 grafts per hour) has 439

16

been developed and used commercially for tomato in the Netherlands (ISO GROEP). With increasing demand 440

of grafted plants, faster, more reliable, and more flexible automation of grafting operations is one of the key 441

technologies need to develop in the future. 442

Fig. 8. Semi-automatic grafting machine developed by Helper Robotech in Korea. 443

4.4. Monitoring Graft Success and Acclimatization 444

Proper acclimatization is critical for grafted plants to survive. Acclimatization involves healing of the cut 445

surface and hardening for field or greenhouse survival (Lee and Oda, 2003). Maintenance of proper moisture 446

content before and after grafting is critical for the production of uniform grafted seedlings. Acclimatization may 447

be achieved simply by enclosing the rootstock and scion in a black plastic bag (to avoid heat buildup) until the 448

union is formed. Growers usually achieve acclimatization by use of plastic film coverings (Fig. 9). In many 449

commercial nurseries, the grafted plants, usually in cell trays of 32 to 72 cells, are placed on a greenhouse 450

bench and the trays are sealed with a single layer of semi-transparent high density polyethylene film (0.01 mm 451

or thinner) to reduce the moisture loss and kept sealed for 5–7 days without additional irrigation. Partially 452

shading may be needed during the daytime to avoid excessive heat build-up. 453

454

Fig. 9. Plastic film covering at Uri nursery, Ansung, Korea. 455

456

5. Commercial production and quality of grafted seedlings 457

458

Increasing use grafted seedlings is frequently accompanied by increases in commercial seedling growers, 459

especially plug seedling growers. Since the grafting usually takes additional facilities and techniques, high-460

quality grafted seedlings are usually produced by professional seedling growers rather than individual farmers. 461

The overall quality as well as the price of those grafted seedlings produced by large commercial growers is 462

much higher than those produced by smaller growers or farmers‟ associations. However, the sale of these 463

grafted seedlings grown in cell trays has been grown explosively during the last decades. Even though there are 464

considerable differences in quality of plug-grown seedlings depending upon the growers as well as the substrate 465

17

(Fig. 10), farmers would like to order their seedlings grafted on preferred combinations from the industrial 466

growers. Most of the seedlings are grown in trays of different number of cells. The cell trays in Korea are the 467

same in size and the seedlings are easy to handle for grafting and transport including export and also can be 468

efficiently transplanted by machine. Even though problems arising from the use of grafted seedlings are rather 469

common especially with respect to seedling health and quality of produces, more farmers are purchasing grafted 470

seedlings rather than grafting their own seedlings. 471

472

Fig. 10. Variation of pepper seedlings as affected by different nurseries (A.B.C…) and 473

substrates [own(upper case letters) and commercial (lower case)]. Same scion cultivar seeds 474

were sown in the cell trays at the same date and the seedlings were photographed 50 days 475

after sowing. Note the great variation in seedling vigor depending upon growers and 476

substrate. 477

478

Since more and more farmers are purchasing grafted transplants from professional nurseries, the quality has 479

become one of the keen concerns among the farmers. As clearly recognized in Fig. 10, the quality of transplant 480

varies greatly depending upon the growers. The definition of high-quality seedling would be very complicated 481

task because so many factors are associated with quality evaluation. Seedlings are in the first place normal and 482

abnormal seedlings based upon the external appearance. Various factors influence the outcome of abnormal 483

seedlings. Uniformity in terms of genetic quality and cultural and/or physiological quality are the two major 484

factors influencing seedling quality (Lee, 2007). Mineral deficiency in the soil or substrate, frost damage, 485

heating, mechanical damage, insect damage, chemical treatment injury, declining vigor, pathogen infections, 486

water and temperature stresses, and many others. In vegetable seedlings, the quality of seedling also varied 487

greatly depending upon the kind of crops and types of seedling distribution such as seedlings without soil or 488

substrate, seedlings grown in conventional pots, or seedlings grafted or non-grafted, or seedlings grown in cell 489

trays. The performance check of the seedlings would be the best way to evaluate the seedling quality, but this is 490

almost impossible, because so many other factors also influence the seedling performance after the 491

transplanting. Therefore, the quality of seedlings is mostly evaluated at the time of transplanting or seedling 492

purchase at the commercial nurseries. On the basis of this concept, the high quality seedlings should be uniform 493

in size and traits, proper size or height with thick healthy stem with large thick leaves. The seedling should have 494

well-developed root systems and show good top/root ratio (T/R). Seedlings for fruit production should have 495

18

large number of flowers (female flowers) in good vigor. Those seedlings for leaf such as lettuces and cabbages 496

should not bolt after transplanting. The seedlings should not be exposed to extreme water and/or temperature 497

stresses during their growth stage. 498

One of the conveniently used parameters to evaluate the seedling quality is the ratio of shoot dry weight 499

divided by shoot length. This may be appropriate for tomatoes, peppers, and eggplants. However, in cabbages 500

and Chinese cabbages, different criteria should be adapted and so are the cucurbits. In pepper, six parameters 501

were plotted in a graph based upon image analysis and the shape as well as the total area driven by evaluation 502

of each parameter (Fig. 11). Parameters such as number of expanded leaves, plant height or shoot length, shoot 503

dry weight, shoot dry weight (DW)/plant height, stem diameter, and stem diameter, and chlorophyll contents. 504

Other parameters, if needed, to be added or subtracted from this kind of evaluation based upon image analysis. 505

Perhaps, the critical factor involved in seedling quality is the infection of serious bacterial and viral diseases 506

which may not be easily recognized at the time of seedling purchase. Serious outbreaks of tomato bacterial 507

canker had been reported in Mexico caused by infected seeds, causing closure of a commercial propagation in 508

Mexico who was a main supplier of grafted seedlings (Kubota, 2009, personal communication). Serious 509

outbreaks of cucumber green mottle mosaic virus (CGMMV), a strain of tobacco mosaic virus (TMV), in many 510

parts of the world, causing tremendous damage to the farmers as well as the seed companies who supplied the 511

virus-infected rootstock seeds for watermelon seedling production. Since the spread of these diseases is 512

phenomenal, the presence of a single infected plant can destroy the entire field. Two large seed companies in 513

Korea were bankrupted after serious outbreaks in 1997 and 2000. 514

CGMMV can be transmitted by seeds, contact, grafting, and some other means such as soil and water. Dry 515

heat treatment is the only practical way of eliminating this virus from infected or infection-suspected seeds and 516

has been used routinely for all the cucurbits seeds in Japan and Korea (Kim and Lee, 2000). Production of 517

organic vegetables using pesticide-free seeds can only be performed by using dry heat treatment in various 518

vegetables including lettuce and Brassica crops. However, production, supply, and use of healthy seeds should 519

be the first choice for the production of healthy seedlings, especially in cucurbits and solanaceous crops. 520

Overuse or misuse of bioregulators or chemical inhibitors to suppress the overgrowth of seedlings grown in 521

high-density cell trays (Fig. 12) is another problem to be minimized and replaced by other physical means. 522

523

Fig. 11. Quality determination of pepper seedlings raised by different nurseries by plotting of multiple parameters. 524

19

Fig. 12. Shape of Chinese cabbage seedlings ready for transplanting as affected by diniconazole or tebuconazole 525

treatment. 526

527

6. Conclusion and Prospect 528

529

For decades, vegetable grafting has been successfully practiced in many Asian countries, and is becoming 530

increasingly popular in Europe. Many multinational seed companies are eager to develop and distribute 531

rootstock seeds through their commercial seed catalogs. Identification of compatible multi-disease resistant 532

rootstocks with tolerance to abiotic stresses is a basic requirement for continued success. Watermelon and 533

tomato are the two major vegetables for grafting and worldwide distribution. Grafting in herbaceous plants is 534

routinely practiced in cucumber, melon, oriental melon, greenhouse squash, eggplant, capsicum peppers as well 535

as cactus. Introduction of excellent rootstocks possessing multiple disease resistance and efficient grafting 536

machines including grafting robots will greatly encourage the extended use of grafted vegetables over the 537

world. There are many problems commonly associated with vegetable grafting and cultivating grafted seedlings 538

(Lee, 1994; Lee and Oda, 2003; Davis et al., 2008). These include the additional cost for rootstock seeds, labor 539

required for the grafting and raising grafted seedlings, lack of experience and technique for grafting and 540

cultivation of grafted plants, and incidence of possible physiological disorders associated with grafting. 541

However, there are enormous benefits from using grafted seedlings. These include income increase by high 542

yield and off-season growing, lower input of fertilizers and irrigation water due to the wide root systems of the 543

rootstocks, considerable saving in agrochemicals due to high resistance of the rootstocks, extension of the 544

harvest period, efficient maintenance of popular cultivars against diseases and other physiological disorders, no 545

need for long-term crop rotations, overcoming problems due to saline soils, reduced expense needed for soil 546

fumigation, ease of producing organically-grown vegetables, and reduced use of agrochemicals. Partial or full 547

take of these benefits will depend upon various factors such as farm size and degree of mechanization, 548

cultivation practices such as crop rotation and transplanting, technology level, understanding the full benefits 549

and risks of grafted seedlings, and the uses of protected cultivation and hydroponics. Use of grafted seedlings is 550

strongly recommended for hydroponics culture of tomato, pepper, eggplant, and cucumber. 551

Growers can now purchase grafted seedlings of any specific combination from many commercial plug 552

seedling growers rather than doing the tedious grafting themselves although growers need to place orders in 553

20

advance in most cases. This is especially true in Japan, Korea, and the Netherlands. With the invention of more 554

efficient grafting robots and acclimatization facilities, the price of grafted seedlings could be considerably 555

reduced in the future to meet grower expectations (Lee and Oda, 2003). Positive use of grafted seedlings can 556

solve much of the problems arising from conventional cultivation such as use of methyl bromide for soil 557

sterilization, incidence as well as the rapid spread of diseases caused by successive cropping, low soil 558

temperature damage during the early stages, heavy use of pesticides and chemical fertilizers, and economic use 559

of irrigation water. For organic produces, the seeds of both scion and rootstock may be treated with dry heat to 560

eliminate seed-borne diseases such as Fusarium and viruses. Effective dry heat treatment method has been 561

developed (Lee, 2003) and rapid detection technique on the inactivation of some seed-borne virus, such as 562

cucumber green mottle mosaic virus, has also been established. Even though the benefits of using grafted 563

seedlings are now fully recognized over the world, production of uniform, healthy grafted seedlings at 564

reasonable prices is the key point for wider use, especially in those countries with limited experience. Visitors 565

were eager to learn the modern grafting technology as well as the labor-saving grafting practices here in Korea. 566

The demonstration of grafting technology as well as the grafting machines and robots during the exhibition 567

period of the International Horticultural Congress of the International Society for Horticultural Science, held at 568

COEX in August, 2006, was well participated by scientists from all over the world (Lee et al., 2007). 569

570

571

572

573

574

575

576

577

578

579

580

21

References 581

Ashita, E. (ed.), 1927. Grafting of watermelons. Korea (Chosun) Agricultural Newsletter 1, 9 (In Japanese). 582

Chung, H. D., Lee, J.M., 2007. Rootstocks for grafting. p. 162-167. Horticulture in Korea. Published by the 583

Korean Society for Horticultural Science. 584

Cushman, K. E., Huan, J, 2008. Performance of four triploid watermelon cultivars grafted onto five rootstock 585

genotypes: Yield and fruit quality under commercial growing conditions. Acta Hort. 782, 335-342. 586

Davis, A. R., Perkins-Veazie, P., Sakata, Y., López-Galarza, S., Maroto, J. V., Lee, S.G., Huh, Y.C., Sun, Z., 587

Miguel, A.,. King, S. R , Cohen, R.,. Lee, J.M., 2008. Cucurbit grafting. Critical Rev. Plant Sci. 27, 50-74. 588

Heo, Y.C., 2000. Disease resistance of Citrullus germplasm and utilization as watermelon rootstocks. Ph. D. 589

Diss., Kyung Hee Univ., Korea (In Korean with English summary). 590

Hoyos Echeverria, P., 2010. Spanish vegetable production: Processing and Fresh market. Chronica 591

Horticulturae 49 (4), 27-30. 592

Ito, T., 1992. Present state of transplant production practices in Japanese horticultural industry. In Transplant 593

Production Systems (eds. Kurata and Kozai). Kluwer Academic Publishers p. 65-82. 594

Kato, T., Lou, H., 1989. Effect of rootstock on the yield, mineral nutrition and hormone level in xylem sap in 595

eggplant. J. Japan. Soc. Hort. Sci. 58, 345-352. 596

Kim, D.H., Lee, J.M., 2000. Seed treatment for cucumber green mottle mosaic virus (CGMMV) in gourd 597

(Lagenaria siceraria) seeds and its detection. J. Kor. Soc. Hort. Sci. 41, 1-6. 598

Ko, K.D., 1999. Response of cucurbitaceous rootstock species to biological and environmental stresses. Ph. D. 599

Diss., Seoul Nat'l Univ., Korea. 600

Ko, K.D., 2008. Current status of vegetable seedling production in Korea and its prospects. Inaguration 601

Seminar of Korean Plug Growers Assoc. June. 2008. 602

Kubota, C., McClure, M.A., Kokalis-Burelle, N., Bausher, M.G., Rosskopf, E.N., 2008. Vegetable grafting: 603

History, use and current technology status in North America. HortScience 43, 1663-1669. 604

Lee, J.M., 1994. Cultivation of grafted vegetables. I. Current status, grafting methods, and benefits. 605

HortScience 29, 235-239.Lee, J.M., 2003. Advances in vegetable grafting. Chronica Hort. 43 (2), 13-19. 606

Lee, J.M., 2008. Vegetable grafting: A powerful aid for cultivation of environmentally-friendly produce. KAST 607

Rev. Modern Sci. Technol. 4, 68-85. The Korean Academy of Science & Technology. 608

Lee, J.M., Bang, H.J., Ham, H.S., 1998. Grafting of vegetables. J. Japan. Soc. Hort. Sci. 67, 1098-1114. 609

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Lee, J.M., Kubota, C., Tsao, S.J., Vinh, N. Q., Huang, Y., Oda, M. 2008. Recent Progress in Vegetable 610

Grafting. International Workshop on Development and Adoptation of Green Technology for Sustainable 611

Agriculture and Enhancement of Rural Entrepreurship. 21 pp. IRRI, Los Bańos, Laguna, Philippines. 612

September 28 – October 02, 2009. Lee, J.M., Oda, M. 2003. Grafting of herbaceous vegetable and 613

ornamental crops. Hort. Rev. 28, 61-124.Lee, S. G., 2007. Production of high quality vegetable seedling 614

grafts. Acta Hort. 759, 169-174. 615

Morra, L., Bilotto, M., 2009. Mercato in fortissimo ascesa per I portinnen sti Orticoli. Edizioni L‟informatore 616

Agrario S.p.A. 2009-1, 51-54. 617

Sakata, Y., Ohara, T., Sugiyama, M., 2007. The history and present state of the grafting of cucurbitaceous 618

vegetables in Japan. Acta Hort. (ISHS) 731, 159-170. 619

Salehi-Mohammadi, R., Khasi, A., Lee, S.G., Huh, Y.C., Lee, J.M., Delshad, M., 2009. Assessing survival and 620

growth performance of Iranian melon to grafting onto Cucurbita rootstocks. Kor. J. Hort. Sci. Technol. 27 621

(1), 1-6. 622

Tachibana, S., 1982. Comparison of root temperature on the growth and mineral nutrition of cucumber cultivars 623

and figleaf gourd. J. Japan. Soc. Hort. Sci. 51, 299-308. 624

Yoshioka, H., 2001. Present status of vegetable production using grafted plants in Japan (in Japanese). Agr. & 625

Hort. 76, 342-348. Oda, M., 2007. Vegetable seedling grafting in Japan. Acta Hort. 759, 175-180. 626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

23

647 Table 1. Purpose of grafting in vegetables (Heo, 2003; Lee, 1994; Lee et. al., 1998; Lee and Oda, 2003). Direct response or effect Indirect response or effect

Shoot growth promotion

Disease tolerance

Low temperature tolerance

High temperature tolerance

Enhanced mineral uptake

High salt tolerance

Increasing fertilizer uptake efficiency

Wet soil tolerance

Enhanced water uptake

Root nodulation

Winter hardiness

Xylem sap composition

Nematode tolerance/resistance

Juvenile and adult phase changes

Translocation studies or stimuli

Sex expression

Hormonal regulation

Physiological changes or disorders

Organic substances; translocation & composition

Propagation and transformation

Fruit yield and quality

Heritable changes or agent(s)

Ornamental value

Earliness

Fruit size control

Extended harvest period

648

649 Table 2. Cytokinin composition in xylem sap collected from intact and grafted plants of cucumber, squash,

and figleaf gourd plants.

Crop

(Scion/rootstock)

Cytokinin content (ng/ml sap)

Zeatin

Zeatin

riboside

Dihydozeatin

riboside

Isopentenyl

adenine Total

Cucumber (Cucumis sativus) 0.08 4.55 0.80 Trace 6.11

Squash A (Cucurbita moschata) Trace 3.67 0.43 3.63 7.73

Squash B (Cucurbita maxima) Trace 4.06 0.57 1.84 6.47

Figleaf gourd (Cucurbita ficifolia) Trace 4.54 1.48 6.18 12.2

Cucumber/Cucumber 0.55 5.58 0.96 Trace 7.07

Cucumber/Squash A 1.65 4.29 0.20 Trace 6.14

Cucumber/Squash B Trace 5.36 0.19 Trace 5.55

Cucumber/Figleaf gourd 1.49 5.08 0.65 Trace 7.22

650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675

24

Table 3. Rootstocks for cucurbitaceous crops and some related characteristics (Lee and Oda, 2003). Scion/Rootstock Cultivar a Major characteristics Possible disadvantage

Watermelon

Bottle gourd (Lagenaria siceraria)

FR Dantos, Dongjanggoon, Bulrojangsaeng,

Vigorous root system, resistant to fusarium and low temperature

New fusarium race, Susceptible to anthracnose

Squash (Cucurbita

moschata)

Chinkyo, No. 8, Keumkang

Vigorous root system, resistant to

fusarium and low temperature

Poor fruit shape and

quality Interspecific hybrid

squash (Cucurbita

maxima x C. moschata)

Shintozwa, Shintozwa #1,

Shintozwa #2, Chulgap

Vigorous root system, resistant to fusarium

and low temperature, excellent vigor and

high temperature tolerance

Reduced fertilizers required,

reduced quality

Pumpkins

(Cucurbita pepo)

Keumsakwa, Unyong,

Super Unyong

Vigorous root system, resistant to

fusarium and low temperature

Poor fruit shape and

quality

Wintermelon (Benincasa hispida)

Lion, Best, Donga

Good disease resistance

Incompatibility

Watermelon

(Citrullus lanatus)

Kanggang, Res. #1,

Tuffnes, Ojakkyo Fusarium tolerance, but not resistance

Not enough vigor and disease

resistance African horned (AH)

cucumber

(Cucumis metuliferus)

NHRI-1

Excellent fusarium resistance and

good nematode tolerance

Medium to poor graft

compatibility

Cucumbers

Figleaf gourd

(Cucurbita ficifolia)

Heukjong (black seeded,

figleaf gourd)

Good low temperature tolerance

and disease resistance

Narrow graft compatibility

Squash (C. moschata)

Butternut, Unyong #1, Super Unyong

Good fusarium tolerance and „bloomless‟ fruit skin

Affected by Phytophthora

Interspecific hybrid

squash (C. maxima x C. moschata)

Shintozwa, Keumtozwa,

Ferro RZ, 64-05 RZ, Gangryuk Shinwha

Good fusarium and low

temperature tolerance

Slight quality reduction

expected

Bur cucumber

(Sicyos angulatus)

Andong

Good fusarium tolerance, low and

high soil moisture tolerance and nematode tolerance

Reduced yield

AH cucumber

(Cucumis metuliferus)

NHRI-1

Excellent fusarium resistance

and good nematode tolerance

Weak temperature

tolerance

Melons-Oriental Melons

Squash (Cucurbita

moschata)

Baekkukzwa, No. 8,

Keumkang, Hongtozwa

Good fusarium and low temperature

tolerance

Phytophthora infection

Interspecific hybrid squash (Cucubita maxima

x C. moschata)

Shintozwa, Shintozwa #1, Shintozwa #2

Good fusarium resistance, low and high soil temperature tolerance, and high soil

moisture tolerance

Phytophthora infection, poor fruit quality

Pumpkin (Cucurbita pepo)

Keumsakwa, Unyong, Super Unyong

Good fusarium resistance, low and high soil temperature tolerance, and high soil

moisture tolerance

Phytophthora infection

Melon (Cucumis melo)

Rootstock #1, Kangyoung,

Keonkak, Keumgang

Fusarium tolerance and good

fruit quality

Phytophthora problem

AH cucumber (Cucumis metuliferus)

NHRI-1

Good fusarium tolerance, low and high soil moisture tolerance and nematode tolerance

Weak temperature tolerance

a Cultivars vary greatly depending upon countries, growing types, years, and grafting methods. 676 677 678 Table 4. Rootstock species and number of registered rootstock cultivars for cucurbitaceous crops in China (Bie, 2010, 679 Personal communication). 680 Crop

Rootstock

Watermelon Cucumber Melon Bitter

melon

Summer

squash

Wax gourd Sponge

gourd

Lagenaria siceraria 6 2 0 0 0 0 0

Cucurbita moschata 4 5 6 2 0 2 0

C. maxima x moschata 4 2 5 0 0 0 0

C. maxima 1 1 0 0 0 1 0

Citrullus lanatus 1 0 0 0 0 0 0

Cucurbita ficifolia 0 7 1 1 1 1 1

Luffa acutangula 0 0 0 2 0 0 0

Luffa cylindria 0 0 0 3 0 0 0

681 682 683 684 685 686 687

25

688 689

690

Table 5. Response of cucurbits to biological and environmental stresses.

Fusarium Nematode Low

temp

tolerance

High

salt

tolerance

Graft compatibility

Rootstock

and scion I a II III IV

M.

incognita

M.

halpa Watermelon Cucumber

Oriental

melon Rootstock b

Shintozwa HRc HR HR HR S S HR HR HCd HC HC Hongtozwa HR HR HR SR S S MR MR SC HC HC

Figleaf gourd MR SR MR SR S S HR HR IC HC IC

Bottle gourd MR HR HR SR S S SR MR HC HC IC Wax gourd HR MR HR HR S SR SR SR HC HC -

Bur cucumber HR HR HR HR S HR SR SR HC MC HC

AH cucumbere HR HR HR HR S MR SR ? HR HC HC

Scion

Watermelon S SR HR HR HR SR S SR - - -

Cucumber HR SR HR HR S S HR SR - - - Oriental melon HR HR S HR S S S S - - - a I, Fusarium oxysporum f. sp. niveum; F. oxysporum f. sp. cucumerinum; III, F. oxysporum f. sp. melonis; and IV, F. oxysporum f. sp. lagenariae. b Shintozwa (Cucurbita maxima x Cucurbita moschata), Hongtozwa (Cucurbita moschata), figleaf gourd (Cucurbita ficifolia), bottle gourd

(Lagenaria siceraria), wax gourd (Benincasa hispida), bur cucumber (Sicyos angulatus), and AH cucumber (Cucumis metuliferus). c HR, highly resistant; MR, moderately resistant; SR, slightly resistant; and S, susceptible. d HC, highly compatible; MC, moderately compatible; SC, slightly compatible; and IC, incompatible. e AH: African horned cucumber.

26

Table 6. Rootstocks for solanaceous crops (Lycopersicon, Solanum, Capsicum, and Datura) and their performances (Lee and Oda,

2003).

Rootstock Scion Performance Reported by

L. esculentum Tomato Modify boron absorption Brown et al. 1971

L. esculentum Tobacco Nicotine & alkaloid absorption affected Dawson 1942

L. esculentum Tomato High temperature tolerance Okimura et al. 1986

L. hirsutum Tomato Resistant to corky root disease Harrison & Burgess 1962

Solanum spp. Tomato Resistant to bacterial wilt & nematode Yield increase

Tikoo et al. 1979 Matsuzoe et al. 1993a

S. sodomaeum Tomato Growth & yield reduction Shackleton 1965

S. auricularum Tomato Growth & yield reduction Shackleton 1965

S. laciniatum Tomato Resistant to water-logging Shackleton 1965

S. melongena Tomato Growth & yield reduction Abdelhaffz et al. 1975

S. integrifolium Tomato Sugar content increase Oda et al. 1996

S. sisymbrifolium Tomato Disease resistance, no effect on sugar content Matsuzoe et al. 1996

S. torvum Tomato Disease resistance, no effect on sugar content Matsuzoe et al. 1996

S. toxicarium Tomato Disease resistance, no effect on sugar content Matsuzoe et al. 1996

S. melongena Eggplant Multiple disease resistance Monma et al. 1997

L. hirsutum × L.

esculentum

Tomato Low Fusarium infection Harrison & Burgess 1962

L. esculentum × L.

hirsutum

Tomato Multiple disease resistance Gindrat et al. 1977

Tomato Resistant to corky root (K), Root knot nematode

(N), Verticillium wilt (V), and Fusarium wilt (F) Yield increase

Bravendoer 1962

Tomato Low & high temperature tolerance Okimura et al. 1986

Tomato Resistance to tomato brown root rot Kuniyasu & Yamakawa 1983

S. torvum × S. sanitwongsei

Eggplant Resistance to bacterial wilt Monma et al. 1997

S. integrifolium × S. melongena

Eggplant High temperature tolerance Okimura et al. 1986

Capsicum spp. Sweet pepper (green)

Compatible with Capsicum only Beyries 1974

C. annuum × C. chinensis

Green pepper Superior growth & yield Yazawa et al. 1980

Datura patula Tomato Low yield Kramer 1957

691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724

27

Table 7. Vegetable cultivation area, number of total seedlings, and number of grafted seedlings needed in

Korea and Japan. Approximate 40 million grafted seedlings are estimated to be used in North American

greenhouses (Kubota, 2008) a.

Vegetable Cultivation

area-2000

Cultivation

area-2005

No. of

seedlings

per ha

(x1000)

Maximum no.

of seedlings a

(million)

% use of

grafted

Seedlings a

2005

Maximum no.

of grafted

seedlings a

(million)

Republic of Korea a

Watermelon 30,451 23,179 6~ 9 208.6 95 198.2

Melon b 13,800 13,000 7~10 130.0 90 117.0

Cucumber 7,269 5,853 20~30 175.6 75 131.7

Tomato 4,916 6,749 20~30 202.5 25 50.6

Eggplant 1,100 933 10~20 18.6 20 3.7

Pepperx 80,130 67,023 20~40 2681.9 10 268.2

Sub-Total 766.3

Japan

Watermelon 16,900 13,400 6~ 9 120.6 92 111.0

Melon b 13,800 10,400 7~10 104.0 30 31.2

Cucumber 15,200 13,400 20~30 402.0 75 301.5

Tomato 13,600 13,000 20~30 390.0 40 156.0

Eggplant 13,300 10,400 10~20 208.0 55 114.4

Pepper c 4,110 3,620 20~40 144.8 5 7.2

Sub-Total 721.3 a 75 ha of area belonging to 135 growers. 725

b Including net melons, cantaloupes, oriental melons. 726

c Including hot peppers for dry and fresh uses. 727

728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766

28

Table 8. Current status of the estimated use of grafted vegetables in some Asian and other countries and regions

as of 2010 a.

Crop Item Japan Korea China Taiwan USA

Watermelon Acreage (ha) a 13,000 20,756 2,162,456 13,431 50,810

Graft % b 92 95 20 35 NA

c

Grafting method d HIG,S HIG,TAG HIG,TAG,SG HIG,TAG,SG -

Rootstocks e Ls,Cl Ls,Cmm Ls,Cl Cmm, Ls -

Cucumber Acreage (ha) 12,800 5,630 1,702,777 2,666 59,480

Graft % b

75 75 30 11 NA c

Grafting method d TAG,SG SG, TAG HIG, TAG TAG -

Rootstocks e Cmm,Cf Cmm,Cf Cm,Sa,Cf A -

Melons Acreage (ha) 10,500 6,607 570,874 6,441 35,790

Graft % b

30 90 5 0.1 NA c

Grafting method d TAG,SG SG, TAG HIG - -

Rootstocks e Cmm,Cm Cmm Cm,Cmm,Cl - -

Bitter melon Acreage (ha) NA c NA

c 200,000 1,802 NA

c

Graft % b

- - 2 30 -

Grafting method d - - HIG, TAG TAG,CG -

Rootstocks e - - Lc La, Cm -

Pickling melon Acreage (ha) 232 NA c NA

c NA

c NA

c

Graft % b

- - - - -

Grafting method d TAG - - - -

Rootstocks e - - - - -

Tomato Acreage (ha) 12,700 6,144 1,454,533 4,235 330 f

Graft % b

40 25 1 25 70 f

Grafting method d SG, TAG SG SG HIG, SG SG

Rootstocks e Le, St Le, Ss Le Ss, Le Ss

Eggplant Acreage (ha) 10,800 325 1,051,537 1,503 2,200

Graft % b

55 20 1 1.3 NA c

Grafting method d SG, TAG SG SG - -

Rootstocksv Ss Ss St - -

Pepper Acreage (ha) 3,620 61,023 16,625 2,405 32,140

Graft % b

5 10 1 2.5 NA c

Grafting method d SG, TAG SG SG - -

Rootstocks e Ca Ca,Cs Cf - -

Data supplied by M. Oda JM Lee Z. Bie and

Y. Huang

SJ Tsao C. Kubota

and M.

Bausher a Cultivation area was obtained from FAO Statistics 2008 except Taiwan. Other countries actively using grafted vegetable 767 seedlings include Vietnam (6,000 ha out of 20,000 ha tomato production area is planted with grafted plants in Vietnam) 768 and possibly many others. 769

b Percentage of cultivation area with grafted plants. 770

c Data not available (NA). 771 d Major grafting methods are TAG:Tongue Approach Grafting, SG:Splice Grafting, HIG: Hole Insertion Grafting, and CG: 772

Cleft Grafting, respectively. 773 e Rootstocks are Cf: Cucurbita ficifolia, Cm: Cucurbita moschata, Cmm: Cucurbita maxima x C. moschata, Cl: Citrullus 774

lanatus, La: Luffa aegyptiaca, Lc: Luffa cylindrica, Le: Lycopersicum esculentum, Ls: Lagernaria siceraria, Sa: Sicyos 775 angulatus, Sm: Solanum melongena, Ss: Solanum species including interspecific hybrids, and St: Solanum torvum, 776 respectively. 777

f Greenhouse hydroponic tomato cultivation area only. Little or no grafting had been reported for field tomatoes of 162,580 778

ha in the USA. 779 780 781 782 783 784 785 786 787

29

Table 9. Current statusa of the estimated use of grafted vegetables in some European and other countries

b as

of April 30, 2009.

Crop Item Spain Italy France Netherlands

Watermelon Acreage (ha) 16,100 11,091 186 NA a

No. of grafts (million) 48.2 10.0 NA NA

Rootstocks b

RS-841

Shintoza

Strongtosa

Macis

RS-841

Shintoza

NA NA

Melons Acreage (ha) 38,600 28,199 14,747 3086

No. of grafts (million) 2.5 8.2 NA NA

Rootstocks b RH-841

Shintoza

Strongtosa

Shintoza

Camelforce

Dinero

RS-841

TZ-148

Dinero

NA

Cucumber Acreage (ha) 7,000 2,065 631 NA

No. of grafts (million) 0.5 0.8 NA NA

Rootstocks b Azman

Hercules

Titan

NA NA NA

Tomato Acreage (ha) 55,300 115,477 4,122 1,800

No. of grafts (million) 72.8 15.1 50% 75%

Rootstocks Maxifort

Beaufort

Beaufort

Maxifort

He-Man

Maxifort

Beaufort

NA

Eggplant Acreage (ha) 3,500 10,862 417 115

No. of grafts (million) 1.8 11.8 65% 75%

Rootstocks Torvum Vigor

Beaufort

Espina

Salutum

STT3

Beaufort

Brigeor

Maxifort

NA

Pepper Acreage (ha) 24,100 11,721 NA 41

No. of grafts (million) 4.0 1.2 NA NA

Rootstocks Atlante Tresor

Rocal

Atlante

Tresor

Galaxy

Snooker

NA

Other Note c,d

Price and Planting c,d

Information in this table was obtained by contacting seed companies, related horticultural agencies, seedling

producing nurseries, and personal communications. Acreage was obtained from FAO Statistics 2008. 788 a Data not available as of April 2010 are marked “NA” in the cell. Other countries actively using grafted vegetable seedlings 789

include Turkey (50% of watermelons), Belgium (mostly tomatoes), Germany, Switzerland, Denmark, and UK (50% or 790 higher), and Morocco (also for export). 791

b Seed companies supplying the rootstocks seeds are Seminis, Syngenta, Nunhems, Clause/Tezier, De Ruiter, Rijk Zwaan, 792 Ramiro Arnedo, and others. 793

c The price of grafted seedlings varies from 0.6 to 1.0 euro depending upon the crops (Pedro Hoyos Echevarria, 2010). 794 d Number of seedlings planted per hectare varies from 15,000 to 30,000 depending upon the kind of crops and planting 795

densities. Use of double-stemmed tomato grafted transplants may cut down the purchasing expense by half (Pedro Hoyos 796 Echevarria, 2010). 797

798 799 800 801 802 803 804 805 806 807 808 809 810 811

30

Table 10. Number of grafted seedlings produced by some major nurseries in Korea in 2008 (unit: thousand).

Nursery Watermelon Cucumber Melon Pumpkin Tomato Pepper Eggplant Total

Hoban 100 5,000 100 200 10,000 200 - 15,600

GreenTek 2,500 3,000 - - 500 3,000 - 9,000

Nosung 4,000 300 - 700 300 - - 5,300

Gongju 1,500 1,000 500 - 1,000 - - 4,000

Yeoju 600 1,000 - - 1,200 200 1,000 4,000

Pureun a 300 500 - - 1,000 1,000 - 2,800

a Major exporter in Korea. 812 813 Table 11. Grafting seedlings produced by different grafting methods in Japan (revised from the survey data of

Yoshioka, 2001).

Crop

Area

surveyed b

(ha)

Percent share of grafting methods a

(%)

Tongue

approach

Split Hole

insertion

Root-removed &

insertion

Splice Others &

unknown

Grafted seedlings produced by farmers for their own use

Watermelon 9,244 7 1 53 38 - -

Cucumber 6,648 89 1 5 4 1 0

Melons c 1,715 56 16 27 1 - -

Tomato 2,412 36 13 6 - 45 0

Eggplant 2,034 3 79 7 - 10 1

Grafted seedlings produced by commercial nurseries for sale

Watermelon 4,455 1 5 35 55 3 1

Cucumber 3,171 14 2 18 26 39 1

Melons c 236 8 14 38 39 2 -

Tomato 2,081 4 4 1 - 90 1

Eggplant 3,436 2 18 8 - 71 1

Sub-total (own use + commercial)

Watermelon 13,699 5 3 47 44 1 0

Cucumber 9,819 65 1 9 11 13 1

Melons c 1,951 50 16 28 6 0 -

Tomato 4,493 21 9 4 - 66 0

Eggplant 5,470 2 41 8 - 48 1 a See Fig. 4 for grafting methods. 814 b Only those who responded to the survey was included. 815 c

Only the field melon data was listed (house melons and greenhouse melons were not listed). 816 817

818

819

820

821

822

823

824

825

826

827

828

829

830

831

832

833

834

835

31

Figures 836

Fig. 1. Adventitious rooting from the melon scion grafted onto squash rootstocks through the hypocotyl cavity

of the rootstock, thus counteracting the grafting effect in some cases (A: left) and rooting from the scion

of the TAG-grafted cucumber onto figleaf gourd (B: right).

837

Fig. 2. Hand grafting of high quality tomato seedlings at Hoban Nursery, Gangwon-do, Korea.

838

Fig. 3. Plug seedlings grown in Morocco for export to southern European countries.

839

840

841

842

843

844

32

Fig. 4. Major grafting methods in cucurbits and solanaceous vegetables.

845

Fig. 5. HIG grafted watermelon seedlings ready for transplanting.

846

Fig. 6. Shape of grafted plant near harvest time (tomato on potato).

33

Fig. 7. Grafting clips and other aids.

847

Fig. 8. Semi-automatic grafting machine developed by Helper Robotech Co. in Korea.

848

Fig. 9. Plastic film covering at Uri nursery, Ansung, Korea.

849

850

851

34

Fig. 10. Variation of pepper seedlings as affected by different nurseries (A.B.C…) and substrates [own(upper

case letters) and commercial (lower case)]. Same scion cultivar seeds were sown in the cell trays at the

same date and the seedlings were photographed 50 days after sowing. Note the great variation in seedling

vigor depending upon growers and substrate.

852

Fig. 11. Quality determination of pepper seedlings raised by different nurseries by plotting of multiple

parameters.

853

Fig. 12. Shape of Chinese cabbage seedlings ready for transplanting as affected by diniconazole or tebuconazole

treatment.

854