Watermelon Cultivars and their Importance | India

After reading this article you will learn about the important cultivars and their value as preamble to watermelon breeding.

Watermelon cultivars have been described in the vegetable cultivar lists maintained by the American Society for Horticultural Science. Watermelon breeders should obtain and evaluate a sample of the cultivars available to become familiar with the diversity of germplasm. It is also useful to observe the improvement in horticultural traits that been made in cultivars developed over time.

A breeding program usually is started by intercrossing the best cultivars currently available, or by crossing the best cultivars with accessions having one or more useful traits missing from the elite cultivars.

Thus, in the beginning a watermelon breeder will need to obtain seeds of the best cultivars, a set of cultivars developed at different times in the past, a set of accessions from germplasm repositories, and lines with useful or interesting gene mutants.

A survey of popular cultivars in the ten major watermelon-producing states in the United States by D.N. Maynard in 2000 indicated that popular cultivars for commercial production were almost all hybrids, with few open-pollinated cultivars being used commercially.

Popular diploid (seeded) open-pollinated cultivars (‘Allsweet’, ‘Black Diamond’, ‘Cal sweet’, ‘Crimson Sweet’, ‘Jubilee II’, and ‘Legacy’) were grown mostly in one state each, suggesting regional adaptation or local demand. Hybrids generally were grown in several states, suggesting they have wider adaptation.

The ‘Allsweet’ type, generally considered to be of high quality, was most popular. The other popular diploid (seeded) cultivars were ‘Sangria’ and ‘Royal Sweet’ ‘Fiesta’ ‘Mardi Gras’ and ‘Regency’. For triploid (seedless) cultivars, almost half of the cultivars were ‘Tri-X-313’ type.

The most popular triploid cultivars were ‘Tri-X-313’, ‘Summer Sweet 5244; ‘Millionaire’ ‘Genesis’ and ‘Tri-X-Shadow’. Crimson Sweet has been popular in Arab world and also in India. Jubilee type hybrids are quite acceptable in India.

There were no defined cultivars of watermelon before the 1820s. Early cultivars include Black Spanish’ (imported to United States from Portugal in 1827), ‘Carolina’ (available at least since 1827), and ‘Imperial’, ‘Mountain Sprout’, ‘Seminole’, and ‘Mountain Sweet’ (introduced by southern growers from 1840 to 1850).

Other heirloom cultivars include ‘Bradford’, ‘Clarendon’, ‘Odell’, ‘Ravenscroft’, and Souter’. Classic watermelon cultivars include ‘Peerless’ or Ice Cream’ (1860), ‘Phinney Early’ (1870), and ‘Georgia Rattlesnake’ developed by M.W. Johnson in Atlanta, Georgia about 1870.

Planned cultivar development programs began in the United States in 1880 to 1900. Important cultivars developed for the southern United States included ‘Cuban Queen’ developed and marketed by Burpee in 1881, ‘Round Light Icing’ (1885), Kolb Gem’ developed by Reuben Kolb of Alabama in 1885 and marketed by D.M. Ferry, Florida, ‘Favourite’ selected from the cross of ‘Pierson’ x ‘Georgia Rattlesnake’ by Girardeau in Monticello, Florida in 1887, ‘Dark Icing’ developed in 1888 by D.M. Ferry, and ‘Dixie’ selected from the cross of ‘Kolb Gem’ x ‘Cuban Queen’ or ‘Mountain Sweet’ by George Collins in North Carolina and marketed by Johnson and Stokes.

Important cultivars developed for the western United States included ‘Chilean’ (black or white seeded) brought from the west coast of South America and introduced to California in 1900, ‘Angeleno’ developed by Johnson and Musser in Los Angeles, California in 1908, and ‘Klondike Solid’ and ‘Klondike Striped’ of unknown origin developed about 1900.

Important cultivars developed for shipping include ‘Tom Watson’ developed by Alexander Seed Co. in Augusta, Georgia in 1906. and Stone Mountain’ developed by Hastings Co. in Atlanta, Georgia in 1924.

Important cultivars developed in the latter part of last century have built on past accomplishments. Charleston Gray’, ‘Crimson Sweet’, ‘Calhoun Gray’. and ‘Dixielee’ (1979),’ ‘Jubilee’ (1963), and ‘Smokylee’ (1971) have high resistance to Fusarium wilt. ‘Dixielee’ and ‘Sangria’ F1, have dark red flesh.

‘Millionaire’ F13x and ‘Royal Jubilee’ F1, (Seminis) have consistently high yields. ‘Crimson Sweet’ and ‘Sugarlee’ have high soluble solids. Kengarden’ has dwarf vines. Tri-X-313′ F13x’ ) is seedless. ‘Minilee’, ‘Mickylee’, ‘New Hampshire Midget’, ‘Sugar Baby’. and ‘Tiger Baby’ (Seminis) are icebox size. ‘Yellow Doll’ has canary yellow flesh. Sugar Baby or Sugar Baby types hybrids are common in India.

A few developments in US Watermelon breeding programmes and having breeding implications in general are as follows:

The inheritance of watermelon traits has been studied extensively, and single genes of practical importance include A for monoecious vs. andromonoecious sex expression, Ar-1 and Ar-2 for resistance to anthracnose races 1 and 2, C for canary yellow flesh colour, dw-1 and dw-2 for dwarf vines, E for non-explosive rind, F for non-furrowed fruit surface, Fo-1 for Fusarium wilt resistance, g^s for striped green rind pattern, Go for non-golden rind at maturity, M for non-mottled fruit skin, oval rather than elongate fruit shape, Pm for resistance to powdery mildew, s and o for short seeds, Scr for scarlet red flesh. y° for orange flesh, and Y for coral red flesh.

A non-lobed leaf mutant has been reported. It expresses in beginning in the seedling stage and is controlled by a single recessive gene. The single-gene trait can be useful for indication of hybrid plants. Hybrid seeds can be produced on one inbred line used as the female parent and having non-lobed leaves.

If it is pollinated using bee pollination in an isolation block, and the male parent has normal, lobed leaves, then it will be possible to distinguish hybrid from non-hybrid at the seedling stage in the commercial seed lot.

The hybrid seeds can then be planted in excess in grower fields and the non-lobed seedlings (produced by self- or sib-pollination) can be removed to leave just hybrid plants. Alternatively, non-hybrid seedlings can be removed from the flats during transplant production. This will have huge value to seed companies engaged in hybrid seed production using manual pollination.

Watermelon is monoecious, and is naturally cross-pollinated like maize. However, there is not as much inbreeding depression or heterosis as one might expect. This is similar to other cucurbits such as cucumber and melon. It has been suggested that the lack of inbreeding depression is due to the small population size used by farmers during the domestication of the species.

Watermelon plants are large, so only a few plants probably were grown in each area. Therefore, even with monoecious sex expression and insect-pollinated flowers, there would have been considerable inbreeding among the few plants representing the population.

Since there is little inbreeding depression in watermelon, inbred lines are developed using self-pollination with little loss of vigour from the parental population.

Regarding heterosis some estimates have shown a 10% advantage of the hybrid over the high parent, but only for some parental combinations. The small amount of heterosis observed in watermelon hybrids makes hybrids unnecessary for high yielding commercial cultivars since inbreds should perform as well.

However, hybrid cultivars are useful for combining traits inherited in a dominant fashion from the two parents. Examples of such traits include red or canary yellow flesh, resistance to Fusarium wilt and anthracnose, and resistance (actually lack of susceptibility) to powdery mildew. Hybrids also permit the protection of proprietary inbred lines from unauthorized use.

However, one of the most important uses of hybrids is the production of seedless cultivars. The primary method for production of seedless watermelons involves the cross of a tetraploid female parent with a diploid male parent to produce a triploid, which will be sterile, and therefore, seedless. Currently, triploid hybrids are the most practical method for production of seedless watermelons.

Male sterility is useful for the production of hybrid seeds without the requirement for expensive hand pollination. The glabrous male sterile (gms) mutant provides male sterility, but the plants are less vigorous, have poor seed set, and are susceptible to cucumber beetles because they lack hairs. A second male sterile mutant, the Chinese male sterile (cms), has been more useful for hybrid production.

Fruit size is an important consideration in a breeding program since there are different market requirements for particular groups of shippers and consumers.

The general categories are: mini (<4.0 kg), icebox (4.0-5.5 kg), small, sometimes called pee-wee (5.5-8.0 kg), medium (8.0-11 kg), large (11-14.5 kg), and giant(>14.5 kg). Fruit size is inherited in polygenic fashion, with an estimated 25 genes involved. Shippers in the United States work with particular weight categories, such as 8.0-11 kg for seeded and 6.5-8.0 kg for seedless.

‘Sugar Baby’, a small-fruited cultivar popular in some pan of the world, was selected in Oklahoma by M. Hardin in 1956. Such types are still popular. Fruit shape is also an important part of market type. The general categories are round, oval, blocky, or elongate. There is one gene involved in round vs. elongate, with the F1being intermediate (blocky).