关键词: Li-R重组体, 纯合显性不致死, 隐性位点

Abstract: The Li₁ mutant discovered by Griffee and Ligon in 1929 is characterized by its short lint fiber, contorted leaf laminae and a twisted appearance of the branches and stems. It was observed that the homozygous mutant plants appeared slightly smaller than the heterozygous ones. Li₁ mutant has never been observed to produce homozygous Li₁ phenotype by selfing since it was introduced and planted in China. To study the allelic relationship between three fiberless mutant (XZ142 FLM,MD17, and SL1-7-1) genes and Li₁ gene, we crossed the Li₁ mutant with these three fiberless mutants, respectively. From the cross Li₁ × XZ142 FLM, we unexpectedly got a recombinant with all distorted leaves and short lint fibers. And there was no segregation in their F₂ progeny, which indicated that the mutation is homozygous of Li₁ gene. We named this homozygous Li₁ mutantas Ligon lintless recombinant (Li-R). Segregating populations were produced to conduct the inheritance analysis of homozygous-dominant- surviving phenotype of this Ligon lintless recombinant Li-R. Segregation of four F₂s derived from Li-R× XZ142 FLM, Li-R×TM-1, Li-R×Hai 7124, and Li-R×Li₁ indicated that the segregation of the homozygous-dominant-surviving phenotype of Li-Rfit a two locus inheritance model, one locus being the dominant Li₁ and another a new recessive locus derived from XZ142 FLM, and we proposed to name it as li_a. Therefore, the genotype of homozygous-dominant-surviving plant Li-Ris 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, that of the heterozygousLi₁ 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 fiberless seed phenotype.

Key words: Ligon lintless recombinant, Homozygous-dominant-survive, Recessive allele