ALLELIC COMPOSITION OF COTTON AT THE LE1 AND LE2 LOCI
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1989, Crop Science Society of America. All rights reserved. Cotton.(Gossypium spp.).zygotes.bearing.a Le2dav allelle.in.combination with Le1 and/or Le2undergo a physiological reaction resulting in embryo or seedling in viability. All F1 hybrids between cultivated tetraploid cotton (G. hirsutum L. and G. barbadense L., 2n = 4x = 52) and a Le2dav homozygote are inviable. A breeding procedure being developed for mass extraction of doubled haploids of cotton relies on the bio-elimination of F2 hybrids by this complementary lethal system. Success is contingent on the absence of le1le2 gametes from a prospective parent because these alleles are fully compatible with Le2dav. The primary objective of this research was to determine the frequency of le1 and le2 in a representative sample of USA-developed G. hirsutum cultivars. A secondary objective was to determine if the timing of the incompatibility reaction was consistent across genetic backgrounds. Fifty-two cultivars were tested by observing the frequencies of nonviable vs. viable progeny and the timing of necrosis following two types of matings: (i) cultivar le1le1Le2davLe2dav and (ii) (cultivar le1le1le2le2) le1le1Le2davLe2dav. All 52 cultivars were found to be Le1Le1Le2Le2, indicating that the frequencies of alleles le1 and le2 are zero, or nearly so, in USA-developed G. hirsutum germplasm. Results on necrotic development indicated that the cumulative dosage of alleles Le1 and Le2 affected the onset of necrosis in the presence of Le2dav. Because alleles le1 and le2 are rare in American upland cottons, the doubled-haploid breeding system will be applicable to these stocks.
