Genetic Analysis of Homozygous-Dominant-Surviving Ligon Lintless Recombinants in Cotton (Gossypium hirsutum L.)

Abstract

The Ligon lintless-1 mutant (Li₁) mutant discovered by Griffee and Ligon in 1929 is characterized with its short lint fiber, contorted leaf laminae, and a twisted appearance of branches and stems. The Li₁ mutant has never been observed to produce homozygous phenotype Li₁ by selfing since it was introduced in China. From the cross Li₁ × XZ142 FLM, a recombinant with all distorted leaves and short lint fibers was obtained, and there was no segregation in their F₂ progeny. Thus, the mutation was homozygous of Li₁ gene, which was named as Ligon lintless recombinant (Li-R). Three fibreless mutants, XZ142FLM, MD17, and SL1-7-1, were crossed with Li-R to study the allelic relationship between the fibreless mutant genes and Li₁ gene. Segregation of the 4 F₂s derived from Li-R × XZ142FLM, Li-R × TM-1, Li-R × Hai 7124, and Li-R × Li₁ indicated that the segregation of the homozygous-dominant-surviving phenotype of Li-R fit a 2-locus inheritance model. One locus was the dominant Li₁ and another was a novel recessive locus derived from XZ142 FLM, which was named li_a. Therefore, the genotype of homozygous-dominant-surviving plant in Li-R is li_ali_aLi₁Li₁, and that of homozygous-dominant-leathal plant of Li₁ is Li_aLi_aLi₁Li₁. The genotype of XZ142 FLM is li_ali_ali₁li₁, and the genotype of the heterozygous Li₁ mutant found in 1929 is Li_aLi_aLi₁li₁. Segregation analysis of F₂-derived F₃ families from Li-R × TM-1 revealed that li_a is non-allalic to li₃ and n₂, both genes leading to fibreless seed phenotype.