Tri-Species Shuffling of Chromosomes to Study the Effects on Fiber Traits Using Chromosome Substitution Lines

Previous studies revealed difficulties in retention and recombination of alien species germplasm by conventional introgression in upland cotton (Gossypium hirsutum L.) due to incompatibility at the whole-genome level. An alternative approach is to use alien species chromosome substitution (CS) lines, whereby retention and recombination can be differentially increased for a specific chromosome or chromosome segment. Here we report for the first time on the development of a set of CS lines from two alien species in a common genetic background of upland cotton. The overall objective of this research is to report on the chromosomal association of important fiber traits using a partial-diallel mating design among CS lines of G. tomentosum Nutt. Ex Seem (CS-T), a wild tetraploid species endemic to Hawaii, G. barbadense L. (CS-B), a cultivated tetraploid species with improved fiber quality traits, and 'TM-1' (G. hirsutum), the recurrent parent with improved agronomic traits and moderate fiber quality traits. The genetic effects associated with CS lines were dissected into additive, homozygous dominance, and heterozygous dominance genetic effects using an additive-dominance statistical model. Five of six CS-B lines and two of six CS-T lines had significant additive genetic effects on lint percentage, indicating that the respective substituted alien chromosome carried alien alleles with potential to improve lint percentage in upland cotton. Fifty-six percent of 16 different significant additive effects associated with the CS-B lines could be useful to improve fiber traits in TM-1. On the contrary, 40% of 15 significant additive genetic effects of the CS-T lines had potential to improve fiber traits. Results suggested that CS lines can unveil many beneficial alleles harbored cryptically in the other AD-genome species and render them more accessible for research and cotton genetic improvement.