Summer Squash:History,Diversity, andDistribution

Harry S. Paris1

Additional index words. pumpkin,marrow, Cucurbita pepo

Summary. Summer squash (Cucurbitapepo L.) is grown in many temperateand subtropical regions, ranking highin economic importance amongvegetable crops worldwide. A native ofNorth America, summer squash hasbeen grown in Europe since theRenaissance. There are six extanthorticultural groups of summersquash: cocozelle, crookneck, scallop,straightneck, vegetable marrow, andzucchini. Most of these groups haveexisted for hundreds of years. Theirdiffering fruit shapes result in theirdifferential adaptations to variousmethods of culinary preparation.Differences in flavor, while oftensubtle, are readily apparent in someinstances. The groups differ in geo-graphical distribution and economicimportance. The zucchini group, arelatively recent development, hasundergone intensive breeding in theUnited States and Europe and isprobably by far the most widely grownand economically important of thesummer squash.

1Department of Vegetable Crops, Agricultural ResearchOrganization, Newe Ya’ar Research Center, P.O. Box90000, Haifa 31-900, Israel.

Contribution no. 1597-E from the Agricultural ResearchOrganization, Bet Dagan, Israel. The cost of publishing thispaper was defrayed in part by the payment of page charges.Under postal regulations, this paper therefore must be herebymarked advertisement solely to indicate this fact.

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S ummer squash are the ed-ible young (several days pastanthesis) fruit of Cucurbita

pepo, a highly diverse species. An easy-to-grow, short-season crop, summersquash is adapted to temperate andsubtropical climates and is grown inmany regions. According to FAO sta-tistics (Fruit and Vegetable Markets,1992), the worldwide production ofsummer squash exceeded 6,300,000metric tons per annum during the late1980s. More recent figures from avariety of regional and local reportsindicate that production and per capitaconsumption of summer squash haverisen sharply during the past decade.Not only has the cultivation of sum-mer squash expanded markedly incountries in which the crop is familiar,it also has spread to regions whereheretofore summer squash was either aminor crop or not grown. While theUnited States and Mexico, the twocountries to which C. pepo is native, aretwo of the largest producers of sum-mer squash, the countries of the Medi-terranean and Middle East, led by Tur-key, Italy, and Egypt, are responsiblefor one-third of the world’s produc-tion. A conservative estimate of theworldwide value of the summer squashcrop is several billion dollars annually,therefore, summer squash ranks highin economic importance among veg-etable crops.

The immature fruit of variouscucurbits have been used for culinarypurposes indifferent parts of the world.Consumption of immature C. pepo fruitwas probably not the first use of thisspecies when it was domesticated thou-sands of years ago. Nonetheless, theculinary use of young C. pepo fruit is anancient practice (Cutler and Whitaker,1961). Fruit larger and more maturethan those we refer to today as summer

squash may have been consumed ini-tially. To this day, fruit that appear tohave been harvested between 1 and 2weeks after anthesis can be found inmarkets in Mexico.

Summer squash are picked whenthey are shiny, up to 1 week afteranthesis. Dull fruit are generally unsal-able. Although summer squash can beharvested over a wide range of sizes,from <50 g to >400 g, the acceptablesize range is a function of the marketdemand, which is in turn a function ofthe interaction of fruit shape with thepreferred methods of culinary prepara-tion used by the consumers of theregion. The acceptable size range canbe quite narrow, and it differs amongmarkets.

Cucurbita, a New World genus(Whitaker, 1947) of the gourd family,Cucurbitaceae, contains five cultivatedspecies. Cucurbita pepo is the mostdiverse of these species, consisting ofwild forms in the United States andMexico previously classified as sepa-rate species, C. texana Gray and C.fraterna Bailey, respectively, as well asmany of the pumpkins and ornamentalgourds, the acorn squash, and summersquash.

Various terms have been used in-terchangeably for the many forms ofC. pepo, but the uses of these termsoften have not been faithful to theoriginal meanings. This has resulted insome confusion, which hopefully canbe reduced or resolved here.

The term pumpkin is rooted in aGreek and Latin word for a large,round fruit, whereas squash comes fromthe plural form of a native North Ameri-can word for something immature orincomplete. Therefore, the term pump-kin is to be applied to edible Cucurbitafruit that are round or nearly round(spherical, oval, obovate, globe, flatglobe, oblate, flat oblate, etc.), whereasthe term squash should be applied toedible Cucurbita fruit deviating greatlyfrom roundness. With the exceptionsdescribed later, pumpkins almost al-ways are consumed when mature. AllC. pepo squash, except for acorn squashand a few unique cultivars such as‘Delicata’, are consumed when imma-ture.

The term zucchini is the diminu-tive plural of the Italian zucca for pump-kin, squash, or gourd. Zucchini ap-plies to cylindrically shaped fruit, simi-lar to those of the original cultivarsbearing the name zucchini (Tapley et

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Table 1. Extant horticultural groups of summer squash (Paris, 1986).

Group Fruit shape

Scallop Flattened, with scalloped marginsCrookneck Elongated, with narrow, long, slightly to very curved neck, broad distal half, convex distal endStraightneck Cylindrical, with short neck or constriction near the stem end and a broad distal half, convex or pointed distal endVegetable Short, tapered, cylindrical, narrow at stem end, marrow broad at distal end, length-to-broadest width ratio ranging

ii-em 1.5 to 3.0Cocozelle Long to extremely long slightly tapered cylindrical, bulbous near blossom end, length-to-broadest width ratio ranging

from 3.5 to 8.0 or even higherzucchini Uniformly cylindrical, little or no taper, length-to-broadest width ratio usually from 3.5 to 4.5

Fig. 1. An array of summer squash fruitarranged according to the six extanthorticultural groups. Left to right top row:cocozelle, crookneck, scallop; bottom row:straightneck, vegetable marrow, zucchini.

al., 1937). The term cocozelle is thediminutive of cocuzza, which itself isan Italian dialect inversion of zucca.Cocuzza applies to the extremely long-fruited forms of Lagenaria, which areused in Sicily and other parts of Italyfor culinary purposes when young,about 50 cm long (Bianchini andCorbetta, 1976). Cocozelle applies tolong fruit of lesser dimensions. Theterm marrow is used for edible C. pepofruit about 2 weeks past anthesis. Itwas a 19th-century English custom toeat fruit of this age, and the termmarrow is perhaps in allusion to bonemarrow (Stuart, 1987). The term veg-etable marrow is the ii-all, original namefor marrow. I prefer to reserve veg-etable marrow for referring to summersquash forms having fruit of the short,tapered cylindrical shape similar to thatof the English forms that were used asmarrows.

Perhaps in the Cucurbitaceae ingeneral, more so in the genus Cucur-bita, and very definitely so in C. pepo,there is an association between thelength-to-width ratio and the stage ofdevelopment at which the fruit is usedfor culinary purposes (Paris, 1989).Pumpkins as well as acorn squash havea near 1:1 length-to-width ratio and,with certain exceptions, are consumedwhen mature. Vegetable marrows de-viate from this ratio, originally beingused when about half-grown. Zuc-chini, which deviate more, are usedonly when young. Cocozelles, whichdeviate even more, are used whenyoung or very young, with the corollastill attached. Similarly, straightneck,crookneck, and scallop squash, whichalso deviate noticeably from the 1:1ratio, are used only when young. Ap-parently, this trend toward deviationfrom the 1:1 ratio stems from thedesire for more of the colored exocarpand firm mesocarp tissue and less ofthe soft, pulpy interior of developingseeds and placenta.

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On the basis of genetic relation-ships, C. pepo has been subdivided intotwo subspecies, pepo arid ovifera, theformer appearing to be associated witha Mexican origin and the latter with anorigin in the eastern half of the UnitedStates (Decker, 1988 ). Six extant hor-ticultural groups of summer squashhave been recognized on the basis offruit shape (Paris, 1986; Table 1; Fig.1). Of these six, the vegetable marrow,cocozelle, and zucchini groups can beassigned to subspecies pepo and thescallop, crookneck, and straightneckgroups to subspecies ovifera.

Their distinct fruit shapes allowthe summer squash groups to be iden-tified easily in even some of the earliestillustrated botanical works. Much ofthe early historical record of Cucur-bita is indeed from botanical herbals(Paris, 1989). One of the most note-worthy of these tomes, because of theabundance of realistic, quality illustra-tions of various forms and thereforeperhaps best summarizing the Renais-sance depictions of C. pepo, is the com-pilation of Chabrey (1666). As all forms

of C. pepo are pollinated by bees, crosswith one another freely, and producefully fertile offspring, it is amazing thatmost of the summer squash groupshave maintained their identity for hun-dreds of years.

In the scallop group (syn. ‘PattyPan’, ‘Custard’, ‘Cymling’, ‘Patisson’,‘Button’), the fruit are flat, with scal-loped margins (Fig. 2). The history ofthis group in Europe dates to themiddle of the 16th century (Paris,1989). The scallop was represented byat least three distinct forms, one ofwhich was the ‘Golden Bush Scallop’cultivar or very similar form. The twoothers were vining forms having fruitresembling those of the ‘Yellow BushScallop’ and ‘White Bush Scallop’ cul-tivars. The use of immature C. pepo bynative Americans of the Atlantic Coastwas described in the mid-17th cen-

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Fig. 2. Scallop squash. Top left,five yellow, striped fruit of‘Golden Bush Scallop’; top rightthree yellow fruit of ‘Yellow BushScallop’; between them, threeintensely yellow fruit (withintense green ring around theblossom scar) of ‘Sunburst’;bottom left and center, sevenlight green fruit (with fainthint of yellow stripes) of‘Benning's Green Tint’; at the 4o’clock position, two pale greenfruit of ‘White Bush Scallop’.

Fig. 3. Crookneck squash. Twofruit each, left to rigkt (top row)of ‘Pavo’, ‘Early YellowCrookneck’, and ‘Dixie’ and(bottom row) ‘Yellow SummerCrookneck’, ‘Supersett’,‘Ranger’, and ‘Pic-n-pic’.

Fig. 4. Straightneck squash. Twofruit each, left to right (top row)of ‘Creamy’, ‘Early ProlificStraightneck’, and ‘Golden Girl’and (bottom row) ‘Goldzini’,‘Lemondrop’, and ‘Multipik’.

Fig. 5. Vegetable marrow squashOne fruit each, left to right, of‘Bar ‘Oz’, ‘Beirut’, ‘Clarita’,and ‘Katia’.

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tury. During the 18th cen-tury, native Americans ofthe coast and the interiorreportedly used the scal-

lop squash when imma-ture, whereas other formsof Cucurbita were usedor stored when mature.The scallop squash wasfamiliar to the most fa-mous of early Americangardeners, ThomasJefferson (Betts, 1944).From the early 19th cen-tury, scallop squash arementioned more or lesscontinually in gardeningliterature of Europe andNorth America. Scallopsquash had economic im-portance along the Atlan-tic coast of the UnitedStates until about 70 yearsago, but since then ap-pear to have been largelyreplaced by other groups.presently, this group hascommercial importance inAustralia, where it isknown as button squash.For many years, the morefamiliar scallop squashfruit were pale green incolor, but yellow scallopsappear today to be increas-ing in popularity. It is be-coming more and moredifficult to obtain seedsof the old open-pollinatedcultivars such as‘Benning’s Green Tint’,‘Golden Bush Scallop’,‘White Bush Scallop’, and‘Yellow Bush Scallop’. Itis much easier to obtainseeds of the modern hy-brids, ‘Peter Pan’ and‘Sunburst’, as these areoffered by many seedcompanies.

In the crookneckgroup, the fruit are elon-gated with a slim, long,slightly to very curvedneck, and a broad distalhalf of the fruit, with aconvex distal end (Fig. 3).Typically, the fruit arelight yellow, but as theymature they become in-tense orange and highlywarted. These are not tobe confused with the so-

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called winter crookneck, which be-long to C. moschata (Duch. ex Lam.)Duch. ex Poir., nor with the cushaws,m o s t o f w h i c h b e l o n g t o C .argyrosperma Huber. An illustrationof the C. pepo crookneck appeared inseveral German botanical tomes of the17th century, but as the illustrationcontains a plant and plant parts ofother cucurbit genera, it appears to beof 16th-century style. The earliestrecord known to me from the United

Fig. 6. Cocozelle squash. One fruit each, left toright, smooth nonstriped subgroup ‘Ibis’ and‘Ortolano di Faenza’; smooth stripedsubgroup ‘Cocozelle’, ‘Long Cocozelle’‘Striato Pugliese’, ‘Cocozelle Tripolis’, and‘Striato d’Italia’, ribbed striped subgroup‘Romanesco’, ‘Fiorentino’, and ‘Arte’.

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States is from the letter of T. Matlackto Jefferson in February 1807: “Thelong crooked & warted Squash—anative of New Jersey, which theCooper’s family have preserved andcultivated for a near century. It is ourbest Squash” (Betts, 1944). Accord-ing to Sturtevant (1890), the ‘Sum-mer Crookneck’ cultivar first appearedin a North American seed catalog in1828, and many other references weresoon to follow in the United States andEurope. Two crookneck cultivars wereknown to Naudin (1856), one of vineygrowth and having large fruit and theother of bushy growth and havingsmall fruit; the fruit of both were yel-low and highly warted. The crook-neck have a characteristically distinct,

strong flavor. At present, the crook-neck is the predominant summersquash group in the southeasternUnited States. Several distinct open-pollinated cultivars, sold under thenames ‘Early Yellow Crookneck’, ‘EarlySummer Crookneck’, and ‘YellowSummer Crookneck’, are still in com-merce but most extant cultivars arehybrids, some of the more familiarones being ‘Dixie’, ‘Pave’, and ‘Tara’.‘Dixie’ has been a leading cultivar sinceits release in 1966.

In the straightneck group, thefruit are cylindrical with a short neck orconstriction near the stem end and abroad distal half of the fruit with aconvex and more or less pointed distalend (Fig. 4). The fruit of all cultivarsare light yellow, but as they maturethey become medium to intense yel-low-orange and warted. The color isgenerally more yellow and less orangeand the profuseness of the warts isgenerally less than in the crookneckgroup. An illustration of a slightlynecked, warted, but not pointed fruit,possibly an incipient straightneck form,appeared in a botanical tome pub-lished in France in 1700. The Frenchbotanist A.N. Duchesne illustrated in1770 a mature straightneck fruit,warted and about 34 cm long, a com-ment on which was published later(Lamarck, 1786). A yellow, warted,humpback squash was described inGermany at about the same time. Nomention of the straightneck squashappeared in any writings from NorthAmerica before 1896. The cultivarnames listed by Hansen and Thornber(1901), ‘Long Golden Straightneck’and ‘Straightneck Summer’, were bothconsidered to be synonymous with‘Giant Summer Straightneck’ by Tapleyet al. (1937), who stated that thiscultivar was introduced by seedsmenin 1896, being a selection out of the‘Giant Crookneck’ cultivar. On theother hand, Tapley et al. reported thatseveral straightneck strains that werebeginning to achieve popularity weredeveloped in the decade before theirwriting. Today, the straightneck culti-vars have economic importance in thenortheastern United States. Thestraightneck is favored by some be-cause it is easier to box and pack thanthe crookneck. Almost all extant

Fig. 7. Zucchini squash. Three fruit each, leftto right (top row) ‘Black Zucchini’, ‘FordhookZucchini’, and ‘Nero di Milano’ and (bottomrow) ‘Verde Lungo di Milano’ and ‘Goldy’.

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Fig. 8. Commercial field of zucchini squashnear Bet She’an, northern Israel. Relativelysmall plants with short internodes andupright growth allow for easy management.

straightneck cultivars are hybrids de-veloped by American seed companies,with ‘Seneca Butterbar’, ‘Multipik’,‘Golden Girl’, and ‘Seneca Prolific’being perhaps the most familiar. Oneopen-pollinated cultivar that has per-sisted in commerce is ‘Early ProlificStraightneck’.

In the vegetable marrow group,the fruit have a short, tapered, cylindri-cal shape, narrow near the peduncle,broad near the blossom end, ratio oflength-to-broadest width ranging from1.5 to 3.0 (Fig. 5). Most cultivars havelight green fruit, although there aresome English cultivars with dark greenor striped fruit. Vegetable marrowsappeared in a 1566 painting by JoachimBeuckelaer of Flanders and then in aBelgian botanical tome of 1576. An-other illustration of a vegetable mar-row or incipient vegetable marrowappeared in a botanical tome pub-lished in 1591. After that, there appearto be no original depictions or descrip-tions of this group until some draw-ings made in France by Duchesnearound 1770, brief comments on whichwere published later (Lamarck, 1786),and a detailed description written inEngland by Sabine (1816). From thenon, the vegetable marrow is mentionedcontinually, mostly in Europe but alsoin North American writings. In theJournal of the Royal Horticultural So-ciety of 1913, many vegetable marrowsare described, differing in plant growthhabit (most being viney), plant vigor,fruit color (almost all white or cream)and overall uniformity. Thus, it ap-

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pears that the vegetable marrow un-derwent intensive development andproliferation in number of cultivars inEngland during the 19th century.Tapley et al. (1937) briefly described acultivar from Alexandria, Egypt, andfrom their description it seems to havehad fruit of typical vegetable marrowshape. Today, vegetable marrows areof great economic importance in theMiddle East. In that region, vegetablemarrows are almost always preparedby slicing lengthwise, scooping outthe central pulp and replacing it with astuffing of meat and rice; their short,broad cylindrical shape makes vegetablemarrows ideally suited for stuffing.Open-pollinated cultivars such as‘Beirut’ and ‘Sihi Lavan’ (‘White Bush’)are still available, but the large MiddleEastern market has induced manyNorth American and European seedcompanies to breed vegetable mar-rows. ‘Clarita’, ‘Beida’, and ‘Clairette’are several of the familiar hybrid culti-vars.

In the cocozelle group, the fruitare long to extremely long, cylindricalbut bulbous near the blossom end,and usually slightly tapered. Thelength-to-broadest-width ratio ap-proximates to greatly exceeds 3.5 (Fig.6). This group includes the longestfruited forms of the species. Most ofthem exhibit longitudinal striping ofthe fruit, but light green is fairly fre-quent and other colors occur. Not-withstanding the Italian name, it wasthe French horticulturists who firstdescribed the cocozelle. In 1770,

Duchesne illustrated a mature cocozellefruit, a brief comment on which waspublished later (Lamarck, 1786).Seringe (1847) described the cocozelleas being eaten when only 10 to 14 cmlong. Naudin (1856) described fourcocozelles, two striped and two lightgreen; the existence of several distinctforms indicates that the cocozelle musthave been in cultivation for a consider-able length of time before his writing.Vilmorin (1883), the French seedsman,presented a fine illustration. Tamaro(1901), writing in Italy, described twostriped cocozelles; the 1916 edition isfurnished with Vilmonn’s illustrationand the caption “Cuccuzzella”. In theUnited States, Burr (1863) and Goff(1888) described the cocozelle culti-var ‘Italian Vegetable Marrow’. Tapleyet al. (1937) described two distinctcultivars, ‘Italian Vegetable Marrow’and ‘Cocozelle’ but stated that thesetwo names had not only been usedinterchangeably but also that they infact referred to an entire group ofcultivars, many representatives of whichwere described in catalogs from Italianseed companies. This situation has notchanged. Indeed, probably more di-versity in vegetative and reproductivecharacteristics occurs in the cocozellethan in any other summer squashgroup. Its many varieties can be di-vided into four subgroups: cultivarswith smooth, striped fruit such as‘Striato d’Italia’ and ‘Striato Pugliese’,cultivars with ribbed, striped fruit suchas ‘ R o m a n e s c o ’ a n d ‘LungoFiorentino’, cultivars with smooth,light green fruit such as ‘Alberello diSarzane’ and ‘Ortolano di Faenza’, allfrom Italy, and cultivars with smooth,pale green fruit from Turkey and theformer Yugoslavia. Forms of the ribbed,striped subgroup are used with thecorolla still attached, 1 to 2 days pastanthesis. Cocozelles, because of theirhigh surface area to volume ratio, areused for steaming whole when youngand for stir frying. When somewhatlarger, some develop a characteristicrich, green-vegetable flavor. Hybridcultivars of the various subgroups havebeen developed by Italian seed compa-nies, including ‘Albatros’, ‘Arte’, ‘Ibis’,and ‘Romano’.

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Fig. 10. Closed growth habit of ‘Benning's Fig. 11. Open growth habit of ‘Goldy’Green Tint’ scallop squash. In addition to the zucchini squash. Only a main shoot (at right,main shoot (at top center), there are several rear) occurs; all but the youngest petioles areside shoots (branching to the left at center and horizontal.lower center, and branching toward the rightat lower center). Petioles of all but the oldestleaves are vertical.

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In the zucchini group (syn.courgette), the fruit are long, cylindri-cal, with little or no taper, and a length-to-width ratio approximating or ex-ceeding 3.5 (Fig. 7). Nearly all zuc-chini cultivars have medium green,dark green, or very dark green fruit,although some cultivars from the east-ern Mediterranean area have pale greenfruit and, more recently, cultivars havebeen developed that have intense yel-low fruit. The history of the zucchini isconsiderably shorter than that of thecocozelle. The earliest description ofwhat might have been a zucchini (butperhaps was a cocozelle) cultivar was‘Larnaca’, which was described byNaudin (1856) as being uniformlycylindrical to slightly bulbous and lightin color. It was not until about 1900that a cultivar of the familiar darkgreen zucchini was described, this be-ing ‘Zucca Quarantine Vera Nana’(Tamaro, 1901). This form was said tohave a short stem, with long, slender,cylindrical, dark green fruit, therebyclosely resembling the modern zuc-chini. Tapley et al. (1937) describedtwo zucchini cultivars that had beenlisted first by North American seedcompanies in 1921 and 1931; the namezucchini seemed to have been usedfirst in California, but by 1937 it hadcome to represent a distinct group.Pangalo (1955) considered the zuc-chini to be the most modern group ofsummer squash because all of the zuc-chini cultivars had bush growth habit,a derived characteristic. Although it isthe only recently evolved summersquash group, the zucchini is today themost widely grown and economicallythe most important group of C. pepo.It is grown, to a-greater or lesser ex-tent, probably in every region in whichsummer squash is grown, and is thepredominant form in many parts of theworld. Its long cylindrical shape isadapted to a wide variety of culinaryuses. Some open-pollinated cultivars,such as ‘Black Zucchini’, ‘BlackBeauty’, ‘Fordhook Zucchini’, ‘Nerodi Milano’, and ‘True French’ are stillin commerce, but most of the marketis comprised of over 100 hybrids, re-sulting from breeding that has beenconducted in the United States, Eu-rope, and elsewhere over the past 40years. Many of the so-called zucchinihybrids released in the 1950s and 1960sare actually intergroup crosses betweena cocozelle or a vegetable marrow witha zucchini; these intergroup hybrids,

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by having distantly related parents,exhibit tremendous hybrid vigor. How-ever, they have a somewhat tapered,less desirable fruit shape than purezucchini, either hybrid or open-polli-nated. Among ‘the hybrid cultivarshaving the classic uniformly cylindricalfruit shape are ‘Aristocrat’, ‘Arlesa’,‘Bareqet’, ‘Blackjack’, ‘Dark Star’,‘Diplomat’, ‘Dusk’, ‘Elira’, ‘GoldRush’, ‘Goldy’, and ‘Large’.

Several cultivars having round fruit(pumpkins) and bush growth habit aregrown in Italy and France for con-sumption of the young fruit. Amongthese cultivars of summer pumpkinsare ‘Tondo di Nizza’ (syn. ‘Ronde deNice’), ‘Tondo Chiaro di Toscana’,and ‘Tondo Scuro di Piacenza’. Oneribbed cultivar of summer pumpkin,‘Gourmet Globe’, was commercial-ized in the United States. Like the sum-mer squash and unlike the typical Hal-loween pumpkins that are so well adaptedto carving, these summer pumpkins aredifficult to slice at maturity because theyhave lignified rinds. One of the reasonsthat the summer squash in general are soill-adapted for use when mature is theirlignified rinds. This condition is quitepronounced in the scallop, crookneck,and straightneck groups, whose rela-tively small fruit develop lignified rindsthat are especially thick and also arewarted (Schaffer, 1983).

Some of the old English marrowcultivars, such as ‘Tender’ and ‘True’,were in fact pumpkins that were usedwhen half grown. This use of somepumpkins apparently is derived fromthe ancient use of the primitive landracepumpkins in Mexico. These Mexicanforms have large vines, are late to flower,and produce a relatively low propor-tion of female flowers, have poor pro-ductivity, and are highly susceptible todiseases. The fruit have thick, lignifiedrinds and are usually prominentlyribbed, but vary in fruit shape, size,and color. These primitive pumpkinsprobably are representative, in wholeor in part, of the ancestral forms of thevegetable marrows, cocozelles, andzucchini (Decker, 1985; Paris, 1989).Apparently round-fruitedness has beenfavored in Mexico. After the arrival ofC. pepo in Europe, most notably inItaly, long fruit shape, bush growth,earliness, and productivity were se-lected; variable landraces or local cul-tivars occur in Italy until the present,but they differ sharply from Mexicanstocks in these characteristics.

Breeding summer squash is con-ducted in an increasing number ofcountries, among them the UnitedStates, Mexico, France, Italy, Spain,The Netherlands, Israel, South Korea,and Taiwan. Besides the universal goalsof crop breeding, i.e., increased pro-ductivity, earliness, and disease resis-tance, there are a number of importanthorticultural characteristics that needto accounted for in breeding summersquash. The fruit shape needs to con-form as closely as possible to the idealof the group being bred. Chances forsuccess increase if the fruit color con-forms to the current demands of theparticular target market. Size of theblossom scar should not be excessivelylarge. At harvest, the peduncle shouldseparate easily from the plant stem, ortend to fracture several cm away fromthe fruit. Among the foliar characteris-tics, small plants, short internodes, andbushy, upright growth are essential foreasy management and harvest (Figs. 8and 9). Foliage that is as spineless aspossible is desired for less scratching ofthe fruit when picked. Open growthhabit, a complex characteristic conferredmainly by lack of branching and hori-zontal petiole angle (Figs. 10 and 11 ), isessential for rapid harvest and less dam-age to the fruit when picked (Baggett,1972). Relatively small plant size is pre-ferred, as excessive foliage is unneces-sary for good production and tends tohide the- fruit. Furthermore, the eco-nomic value of the fruit is inverselyrelated to their size, smaller fruit com-manding a higher price in nearly allcases. Large plants, typical of intergroup-hybrid zucchini, tend to have exces-sively fast fruit growth, which results inoversizing of the fruit very quickly.

Breeding summer squash appearsto be more intensive now than everbefore. The 1980s witnessed the re-lease of a number of cultivars, espe-cially of zucchini, with exceptionallygood combinations of the desired traitsenumerated above. Even more recentlythere have been reports of success inbreeding for resistance to virus dis-eases in zucchini and crookneck. Inthe future, one can expect combina-tions of the best horticultural traitswith disease resistance. These elite com-binations probably will be achievedfirst in zucchini. which can be ex-pected to continue as the economi-cally most important and horticultur-ally most advanced group of summersquash.

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