Chromosome Substitution Lines: An Effective Way To Introgress Useful Genes From Other Allotetraploid Species Into Upland Cotton, Gossypium hirsutum L.

Germplasm and Genetic Stocks

oral

Saha, Sukumar; Stelly, David; Wu, Jixiang; Raska, Dwaine; jenkins, Johnie; McCarty, Jack; Makamov, Abdusalom; Gotmare, Vinita; Abdurakhmonov, Ibrokhim; Todd Campbell , Benjamin

Saha, Sukumar

Saha, Sukumar

The exotic gene pools of the tetraploid Gossypium species G. barbadense, G. tomentosum, and G. mustelinum (2n=52), the sanctuaries of many useful genes and genetic variability, have been under characterized and underutilized in the genetic improvement of Upland cotton (G. hirsutum). Cytological evidence and comparative molecular mapping results suggested that structural genomic differences among the tetraploid cotton species are minimal and do not preclude introgression of the alien species gene pools into Upland cotton. Nonetheless, previous interspecific introgression efforts with Upland cotton using conventional breeding methods had limited success, which suggests that many interspecific recombinants do not occur, are "lost", or are selected against under conventional breeding practices. Scientists at Texas A&M University and USDA/ARS, Mississippi State have been collaboratively developing sets of backcrossed chromosome substitution lines (CS) for different chromosomes and chromosome segments of G. barbadense, G. tomentosum and G. mustelinum. Backcrossed five generations to a common inbred, these CS lines are largely isogenic, except for the differences between the substituted pair of chromosomes or chromosome segments in each CS line. Once developed, CS lines can be used in diverse manners for breeding, quantitative genetics and genomics of complex multigenic traits, including agronomic and fiber quality traits. The overall objective of this paper is to report on the field evaluation of agronomic and fiber quality traits of the CS lines. We have used several types of population structure, experimental design and statistical analysis to discover the alien chromosomal effects on important complex traits using the CS lines. The near-isogenic nature of the substitution lines to the common parent TM-1 provides a unique opportunity to use specific mating designs among the CS lines of interest to create different chromosome specific combinations of unique genetic resources. Our results show that the CS lines are useful from several perspectives: 1) to improve genetic diversity for important traits in Upland cotton, 2) to discover the untapped potential of cryptic alleles from the wild and unadapted tetraploid species, 3) to understand the ramifications of epistasis on complex agronomic and fiber traits and 4) to identify chromosomal locations of important fiber and agronomic traits. CS lines can lead to enhanced resolution in linkage mapping and facilitate targeted exploitation of exotic germplasm to improve fiber quality and agronomic traits in cotton breeding program. CS lines thus provide a powerful resource for innovative utilization of genetic resources and a tool to overcome the problem in interspecific introgression in genetic improvement of Upland cotton.