Effect of Tri-Species Chromosome Shuffling On Agronomic and Fiber Traits in Upland Cotton.

Gossypium barbadense (L.), G. tomentosum (Seem.), G. mustelinum (Watt.) and G. darwinii (Watt.), members of the primary gene pool of Upland cotton (G. hirsutum), share a common chromosome number (2n=52), similar AD-genome architecture, and form reasonably fertile F₁ hybrids. However, reduced transmission of the alien germplasm during backcrossing and poor performance of most products due to genetic drag effects are serious impediments in interspecific introgression. We have developed an unique set of chromosome substitution (CS) lines from G. barbadense (CS-B) and G. tomentosum (CS-T) in a uniform genetic background of G. hirsutum (TM-1) which can help to overcome some of these problems associated with conventional methods of interspecific introgression.  Here, we report on the chromosomal effects on important agronomic and fiber traits, based on a partial diallel crossing program among six CS-B lines (CS-B01, CS-B04, CS-B07, CS-B08Lo, CS-B15sh, CS-B18), six CS-T lines (CS-T01, CS-T04, CS-T07, CS-T08Lo, CS-T15sh, CS-T18), and TM-1. The parental lines and F₂ hybrids were planted in a randomized complete block design with four replications in five environments.  We used an additive-dominance (AD) with G*E interaction genetic model for data analysis. The genetic effects were calculated based on the deviations from the population grand mean.  Results revealed that the CS lines harbor useful additive and dominance alleles for specific traits compared to the recurrent parent TM-1.  For example, TM-1 had additive genetic effects for fiber strength -0.280g/tex and lint percentage -0.132, whereas CS-B08Lo had additive genetic effects for fiber strength 1.223g/tex and lint percentage 1.048, respectively. Results revealed that CS lines can be used as a tool to overcome the challenges associated with conventional method of interspecific introgression.