ABSTRACT
The alleles, Le(1) and Le(2), of the cultivated tetraploid cottons, Gossypium hirsutum L. and G. barbadense L. F [genomic formulae 2(AD)(1) and 2(AD)(2)], interact with an allele, Le(dav), from the wild diploid species, G. davidsonii Kell., 2(D(3)), to cause embryonic, or seedling, lethality. Rare accessions of G. barbadense from South America are of the genotype le(1)le(1)le(2)le(2), and these are cross-compatible with G. davidsonii, producing, after crossing with the D(3) species, vigorous, although sterile, triploid plants. Using the D(3) compatibility alleles of the South American cottons, several cultivated stocks of both G. hirsutum and G. barbadense were made cross-compatible with G. davidsonii. Then, using the technique of hexaploid bridging, Le(dav) was transferred from G. davidsonii to the compatible tetraploid cottons to create stocks of the genotype, le(1)le(1)Le(dav)Le(dav). These new stocks proved to be crossincompatible with modern cultivars of G. hirsutum and G. barbadense. Using the D(3) complementary lethality system, stocks of glandless cottons are being bred that are genetically isolated from glanded cultivars. The best of these has lint percentage and fiber properties equal to those of the parental cultivar stock.
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