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- Author or Editor: Perry E. Nugent x
Virescent (v) is inherited independently of yellow-green (yg), glabrous (gl), and halo (h) seedling mutants in muskmelon (Cucumis melo L.). Virescent, yellow-green seedlings were virescent with the yellowish chlorophyll change. Virescent, glabrous seedlings were virescent without trichomes, and virescent, halo seedlings produced no chlorophyll and were lethal. With each pair of mutants the segregation of progenies from test crosses fit the expected ratio for independent assortment of 2 gene pairs located on different chromosomes.
The halo cotyledon mutant of musk-melon, which produced yellow cotyledons with green margins and occasionally with green midribs, was discovered in 1970 (3). Most of these cotyledons turn green within 7-14 days, and subsequent seedling growth is normal. It is a potentially useful marker for genetic studies of the species, for cultivar improvement, and for identifying chance crosses with related species. This study was undertaken to provide information on the genetic relationship of halo (h) to glabrous (gl) (2) and to yellow-green (yg) (5). Plants carrying the glabrous gene are without tricornes throughout their life and those with the yellow-green gene are light yellow-green throughout their life, although their immature fruit are normal green.
Since 1968, three spontaneous 4× melons (Cucumis melo L.) plants were discovered in our field or greenhouse plantings. Two were found in the cultivar Planters Jumbo and one in the virescent marker C879-52. Each of these 4× plants had rounded cotyledons, shorter internodes, thicker stems and leaves, more hairs, and smaller fruits, with larger stem and blossom scars, than their 2× counterparts. Also, their flowers, pollen grains, stomates, and seeds were larger. The discovery of a 4× virescent plant in 1987 allows easier germplasm transfer between ploidy levels. Morphological characteristics of 2× and 4× melons will allow identification without need for chromosome counts.
The southern root-knot nematode, Meloidogyne incognita [(Kofoid & White) Chitwood], causes serious economic losses to melon (Cucumis melo L.) production in the United States. The present study was conducted to determine if separable differences in nematode resistance of Cucumis melo could be found at some inoculum level. Five C. melo lines were compared with Cucumis metuliferus Naud. (C701A), a highly resistant species, for root necrosis, galling, egg mass production, and reproduction when inoculated at 0, 500, 1000, 2000, or 5000 nematode eggs per plant. Using these criteria, melon line C880 inoculated with 1000 eggs per plant was highly susceptible, while PI140471, PI 183311, and the cultivars Chilton, Georgia 47, Gulf Coast, Planters Jumbo, and Southland were less susceptible. In greenhouse tests with an inoculum level of 1000 eggs per plant, low levels of resistance were evident. A thorough screening of the available germplasm against M. incognita may identify higher levels of root-knot nematode resistance for incorporation into improved melon cultivars.
Thirteen triploid lines of melon (Cucumis melo L.) were derived from crosses involving five tetraploid and seven diploid lines. Fruit characters were assessed. When allowed to open pollinate in field plots with adjacent diploid pollinators, eight triploid genotypes were sterile or nearly sterile (<1% viable seed). Five triploid genotypes were partially fertile, indicating viable pollen grains were present. Cytological analysis performed on progeny of a partially fertile triploid plant fertilized by open pollination indicated euploid female gametes were common. Triploid hybrids between tetraploid `Miniloup' and several other diploid parents had vegetative and fruit characteristics intermediate to the parents. Most triploid genotypes yielded round fruit in contrast to their diploid parent whose fruit were oval to oblong and the tetraploid parent that had oblate fruit. Sugar levels of some triploid hybrids were as high as diploid parents.
Natural cross pollination was studied with virescent (v), yellow-green (yg), glabrous (g) and halo (h) muskmelon mutants. The average percent crossing was 8.9,7.6,5.1, and 6.0, respectively. The variation was from 0.0 to less than 20%, except for one fruit with 30%.