Genetic Effects on the Timing of Ledav2 Induced Necrosis of Cotton
- William L. Rooney and
- David M. Stelly
Cotton (Gossypium spp.) embryos carrying the Ledav2 allele in combination with the Le1 allele at the Le1 locus and/or the Le2 allele at the Le2 locus undergo a hybrid lethality reaction, which causes progressive necrosis and death between germination up to 21 d postgermination. Timing of the necrosis is thought to be controlled by the cumulative dosage of alleles Le1 and Le2 interacting with Ledav2, but there have been no studies to identify the exact genetic relationship between the alleles Le1, Le2, and Ledav2 in terms of timing of necrosis induced by the Ledav2 complementary lethality system. The objectives of this study were to determine: (i) if the timing of necrosis is under genetic control of the loci Lel and Le2, and (ii) if the mechanism of timing or mode of gene action is consistent across genotypes. Five cultivars (Le1Le1Le2Le2) were used as sources of Le1 and Le2 alleles. Seedlings from reciprocal crosses of (cultivar ✕ le1le1le2le2) F1 plants and an le1le1Ledav2Ledav2 tester were scored for the presence and timing of the lethal reaction. Frequency histograms were used to phenotypicaily group seedlings according to the time of death. Observed frequencies of the phenotypic groups were tested against frequencies expected for digenic segregation. Results indicated that increased dosage of alleles Le1 and Le2 with Ledav2 hastens necrosis, but variation among cultivars indicated that Le1-Ledav2 and Le2-Ledav2 interactions may not always be distinctly different. Three possible explanations for these differences are: (i) that additional loci are involved, (ii) that allelic action is modified by background genotypic differences, and/or (iii) that the Le1 and Le2 loci are polymorphic.
Copyright © 1990.