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TOPIC: Breeding in Litchi fruit COURSE TITLE : Breeding of fruit crops COURSE NO. : FSc.-506 SUBMITTED BY PAWAN KUMAR NAGAR M.Sc. (Fruit Science) B.A. COLLEGE OF AGRICLTURE
Botanical name : Litchi chinensisFamily : SapindaceaeChromosome no. : 2n= 30Origin : ChinaClimatic adaptability : SubtropicalType of dichogamy : Heterostyle pin and thrum typeType of parthanocapy : StimulativeType of inflorescence : PanicleType of Edible part : fleshy arilType of fruit : One seeded nutRelated species : Rambutan, Longan berryPollination : highly cross pollinationPollinator : honey beeLitchi has two specie : L. chinesis, L. philippinesis (Used as rootstock ) LITCHI
Improved cultivars play vital role in improving production of the crop in a region. They possess built in production stability factors and aid in ensuring high production and better quality. As the crop yield is an integrative and interactive interplay of several factors involving all aspects of cultivation, the yielding potential of a cultivar depends not only on its genetic make-up but also on how it is handled in the field. It has been estimated that contribution of a variety to yield improvement is up to the extent of 30 per cent. The remaining 70 per cent contribution comes through the cultural practices used to produce the crop with that variety.Nevertheless, a contribution of nearly 30% to the yield from a single factor (i.e. cultivar) clearly highlights its role in crop production. In India, genetic base of litchi is narrow. Although nearly 40 cultivars have been reported under cultivation in different parts of the country, only 7-8 varieties are popular and grown commercially in different parts of India. Introduction:
Since litchi originated in China and it has been under cultivation there for more than 2200 years, more than 200 litchi varieties exist in China however, the varieties grown commercially is limited to 15 or 20 only.The variation in climatic factors, sometimes leads to greater fluctuation in yield of a litchi orchard but by and large it is the variety which governs the potential yield and fruit quality of the orchard. Therefore, a right variety should be selected for plantation at a particular lace though, all the litchi varieties have a wide range of adaptability; yield, fruit quality and acceptability may be region or location specific.When distinguishing the cultivar, the shape of skin segments and protuberances are the reliable and stable genetic characteristics.Fruit size, shape and taste are also variables but are influenced by other than genetic factors.
The litchi inflorescence is determinate and composed of several multiple branched panicles on parent season wood. the panicle are produced thermally in cluster of 10 or more , but in some trees a high percentage of auxiliary panicles may also be produced.The time of flower initiation varies with genotypes and environments and environmental conditions. In the northern him sire it usually occurs between june and September.Shahi is early to flower followed by Rose scented, Purabi , Deshi ,Bedana and China in India.The Inflorescence of litchi is well branched panicles bearing numerous ape talus, creamy colored tiny flowers. Different sex from found on panicle sare; Male type MT; Imperfect hermaphrodite with non dehiscent anthers (functionally Female FF; 0 and imperfect female hermaphrodite with abortive ovary (Functionally Female - FF). Floral Biology:
All the flowers of a panicle open in distinct successive flushed and their sexes varies greatly in different successions .In general, first flower that open panicle are MT .This phase is interrupted hermaphrodite flowers functioning as female flower. Each FF flower has two lobed, binocular soupier ovary with a single style bifurcated stigma. FF cycle is interrupted by another cycle of imperfectly hermaphrodite flowers that flower that function as male flower (MF). The proportion of female functional female flowers varies greatly between cultivars and years, formers than 60%.The ban thesis of flowers occurs throughout the day and night with early morning between 6 to 9 am Receptivity o stigma is reached generally after 8 to 10 hours after an thesis and continues upon 42 to 48 hours.
Criteria for Selection of Litchi Varieties:Varietal selection is generally made on the basis of yield potential, disease resistance, suitability for local conditions and availability of planting material in a nearby place and often without sufficient consideration of market preferences and post-harvest behavior particularly the keeping quality. In order to meet the challenge of the present day requirements, some criteria should be considered while selecting a litchi variety. No existing cultivar possesses all these desirable characteristics, some of which may even be strongly influenced by environmental conditions, that is why cultivar selection must be carried out in every region. It is worth pointing out that some characteristics may be more desirable in some areas than in others. The most desirable characteristics of a litchi cultivar are set out in following paragraphs.
Desirable Characteristics of a Litchi Cultivar:A schematic diagram of ideal litchi fruit have been given in whereas the other parameters required for describing any cultivar has been given in:
Fig. External and internal structure of a litchi fruit
Weight: Light weight fruit is an undesirable feature which affects profitability. Any varietal selection for cultivation must include the heaviest weight possibly not less than 25 g. Shape: Round shape is the most efficient shape as it allows for easy packaging and educes transport cost and it should therefore be given preference, however, it is not an absolutely essential characteristic. Varieties of other shapes, oval, or even a sling shape may also be Shape may also be selected.Post harvest quality: Fruit should lend itself well to preservation by freezing so that it can be consumed a fairly long time after harvesting. This is an important factor to be kept in mind while selecting the variety for cultivation.Ripening: Uniform ripening pattern and short ripening period on an individual tree is desirable so that all the fruits on the same trees ripe at the same time. This makes harvesting easier and keeps harvesting cost down.Season of fruit availability: Litchi fruits are harvested in the summer, when there is an abundance of all other fruit. Early or late varieties would therefore be more desirable.
Shelf life: The litchi fruit get deteriorated within short period after harvesting, hence, selected variety should have longer shelf life of fruit.Fruit colour: Bright red fruit colour is the desirable feature as it is pleasing to the eye. Fast skin browning is a demerit. A litchi cultivar should have slow darkening of skin colour after harvesting. This will reduce the need for refrigeration of the fruits immediately after harvesting and would keep export costs down.Skin texture: Skin should have acceptable thickness and texture. It provides adequate protection in the period between harvesting and consumption and allows for easier peeling.Resistance to biotic and abiotic stress: Pest and disease resistant varieties are of prime importance. It is an important factor for the tree as a whole. Fruit should be resistant to cracking and sun-burn. Since the fruits are particularly sensitive to cracking, which is caused By extremes of humidity and temperature, it would be highly desirable to have a variety free from this defect as far as possible.
Seed: Small seed is an essential characteristic for litchi fruit. Of existing cultivars, only those in which the seed accounts for less than 30 per cent of the weight of the fruit (practically more than 70 per cent pulp) should be selected. Since litchi with chicken-tongued seeds do not suffer any loss of quality, this characteristic is very much appreciated. It is influenced to some extent by environment. However, whatever the circumstances, the higher the proportion of this type of fruit obtained the better is the variety. Small seeds are not absolutely essential in large fruits.Taste: Pulp should be of pleasant taste and texture. Fruits that are slightly fragrant, with a sweet or slightly bitter sweet taste, even prior to maturity, are preferred. The pulp should be crisp in texture and not too watery.
Fig: Different type of flower shape
Breeding objective:Breeding objective are to develop varieties with dwarf stature, regular bearer.Through an ideal litchi cultivar for modern requirements is lacking, the following points are to be borne in mind while developing a superior cultivar: large fruit size (>20g) having small seed or highest percentage of aborted seeds, good skin colour, fruit quality and high keeping quality.
Fruit characteristics used to describe different litchi cultivars
Fig: panicle and fruit
Stout panicles with 25 to 30 FF are slated rest all unwanted flowers and bare branches removed and panicles covered with non capsule , water proof cellophane bag to protect from unwanted pollen, Selected flowers are pollinated following emasculation. MT and FM flower are also protected against foreign pollens by covering the with insect proof bags after removing all opened flowers.
Selected flower in lower half of the panicle 20-40 FF per panicle, gives better set then pollination a large number of flowers. Pollination is achieved by placing pollens on the receptive stigmas with the help of a clean cannels hair brush. Fruit setting in crossing can be increasing if the glossy stigma is smeared with 10% sucrose and 10% boric acid solution by a soft hair brush before pollinating. Emasculation and pollination:
In litchi the cycle of FF flowers, is relative short and it is reported for different cultivars to range from 4-6 days in Israel , 5-9 days in Florida 10- 20 days in South Africa and 7-18 days in India in different cultivars. This period or EPP. It is of high practical value as it greatly inflected the success of hand pollination in a breeding programmed. To overcome the problem of unsynchronized flowering in different litchi cultivars, a branch from anther variety with which crossing is top grafted on the tree and bagged with a plastic cover at an early stage of inflorescence developed. Bagged inflorescence flowers earlier then untagged ones. Some honeybees are introduced to effect the pollination inside the cover.Effective pollination period (EPP) in litchi:
Two hybrid namely Madhu and H-73 have been developed as a result of cross between Purabi into Bedana and released for commercial cultivars.Ali , Ziniangxi Mianbaoli and fengli are four new litchi selections made in china.Ali(dwarf), Ziniangxi (large, strongly good eating quality ) ,Mianbaoli (high TSS 17.5%), Fengli(TSS 18%).Other selections made earlier are Songmei 2(long storage life, good eating quality) , Sangmei 5 (larg, strogly aromatic fruits), Songmei 9 (Exceptionally high and stable production) and 12 (dwarf).
Selection and Inter varietal crosses:
Longan cultivars have a strong biennial bearing tendency and thus incorporation of this characters into the hybrid may cause more erratic fruiting.Intergenic crosses between Longana nd Litchi were successful in dialogic crosses.In reciprocal crosses between commercial cultivars of litchi and longan produced hybrid progny only when litchi was used as female parents.Nephelium philippines can provide an important gene pool for breeding work. SeedlessFruit bearing wild forms could have potasial for fruit production for the canning industry.Seedless forms of Pulasan (N. mutabile) can also be used to hybridies with rambutan to produce new types of fruits.N. mutabile and other wild species with rambutan for use as rootstock material, which cold be more resistant to root disease than the rambutan. Intergenic Crosses:
Immature embryo and anthers have resulted in uniform diploid and haploid(n) production.A haploid individual has the potential for early identification and evolution of recessive alleles either naturally occurring or artificially induced, without being masked by dominates on a homologous chromosomes.Doubling of haploids leads to complete homozygous diploids that can be produced without the time consuming take of selfing or sib mating and selection over years. Biotechnology:
Standardization of tissue culture techniques, anthers, embryo, transgenic production.Transfer of gene responsible for fruits with chicken tongue seeds to the commercial litchi cultivars. Future Thrust areas:
Varieties in Litchi
Fig. Litchi Cvs. China
Fig. Litchi Syn. Late Bedana
Fig. Rose Scented variety
Fig. Shahi variety
Fig. Litchi Cv. Bengal
Fig. Litchi Cv. Haak Ip
Fig. Litchi Cv. Heung Lai
Fig. 3.11: Litchi Cv. Groff