Segregation Distortion and Genome Wide Digenic Interactions Shed Light on the Transmission of Introgressed Chromatin From Wild Cotton Species

Cultivated cotton is the world’s foremost textile fiber crop and an important source of oil seed. Narrow genetic diversity has been a major barrier in improvement of cotton. Wild allotetraploid relatives of cultivated cotton are a rich source of genetic diversity and have potential that can be used in cotton genetic improvement, but problems such as linkage drag and segregation distortion are prevalent in interspecific crosses. These problems necessitate knowledge of the pattern of transmission of wild chromatin in recipient species. Here we have analyzed transmission genetics of Gossypium mustelinum in a interspecific backcross population using Gossypium hirsutum as a recurrent parent. The average frequency of G mustelinum alleles over all BC3F2 segregating families is less (39%) than expected (50%). Prevalence of skewed G mustelinum chromatin transmission is confirmed by significant deviation of both genotypic and allelic frequencies from expected ratios 1:2:1 and 0.5:0.5 respectively. Loci with greater segregation distortion are involved in higher numbers of multilocus interactions. Loci lacking homozygotes are more frequent for G. mustelinum than G. hirsutum alleles. Selection against G. mustelinum loci differs in the two ‘subgenomes’ of tetraploid cotton, being significantly stronger for A than D subgenomic loci.