Tri-species shuffling of chromosomes to study the effects on fiber traits using chromosome substitution lines

Authors: Saha, Sukumar; WU, JIXIANG - South Dakota State University; Jenkins, Johnie; McCarty, Jack; Campbell, Benjamin - Todd; Hayes, Russell - Russ; STELLY, DAVID - Texas A&M University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2017
Publication Date: 6/16/2017
Citation: Saha, S., Wu, J., Jenkins, J.N., Mccarty Jr, J.C., Campbell, B.T., Hayes, R.W., Stelly, D.M. 2017. Tri-species shuffling of chromosomes to study the effects on fiber traits using chromosome substitution lines. Crop Science. 57(3):1211-1226.

Interpretive Summary: There is a compelling urgency to develop and deliver suitable cotton varieties to compete with synthetic fibers in the global textile market. Increasing genetic productivity with superior fiber quality are the primary means to meet this future demand given the constraints of challenges on land and water use. In the pursuit of these goals, cotton breeders often confront difficulties to find synergies for providing the genetic diversity to prevent genetic erosion and selecting crosses from closely related high-yielding elite lines in breeding programs. The narrowed genetic base makes sustainable cotton production fragile against biotic and abiotic threats. Interspecific germplasm introgression can greatly expand opportunities to improve genetic diversity in Upland cotton. However, such efforts are constrained by technical and biological limitations due to the genomic incompatibilities among the species. Our previous studies revealed that chromosome substitution is an exceptionally effective means of introgessing valuable genes from other species in Upland cotton. In this report, we have extended this principle by analyzing chromosome substitutions of G. hirsutum involving germplasm from two alien species of Gossypium barbadense (CS-B) and Gossypium tomentosum (CS-T), creating even greater opportunities for breeding use and genetic inference. Partial diallel mating design, as used here among CS-B and CS-T substitution lines with the appropriate AD statistical model analysis provided an effective genetic platform for dissecting genetic effects on fiber traits into additive, homozygous dominance and heterozygous dominance effects for each of the CS-B and CS-T lines. Our results unveiled that chromosomal or inter-locus interactions of potentially interacting alleles played a major role in non-additive mode of genetic regulation of several fiber traits. Sixteen different significant additive genetic effects for fiber traits were associated with the CS-B lines, 56 percent of these effects could be useful to improve fiber traits in Upland cotton. On the contrary, based on the assumption of at least one QTL/additive genetic effect, we observed that 15 QTLs with additive genetic effects were associated with the CS-T lines of which 40 percent had genetic potential to improve fiber traits in TM-1. This study provided new information on the following: 1) novel method of creating unique genetic materials by infusing beneficial alleles from there different species in a common genetic background readily useable by the breeders, 2) a tool in Upland cotton breeding programs for targeted exploitation of useful genes from wild species overcoming some of the problems of genetic drag effects from deleterious genes, and 3) discoveries of cryptic alleles from a wild species and unadapted germplasm with potential to improve Upland cotton, whose effects could not be detected in the donor parents. This research could be useful beyond cotton for exploitation of new and diverse sources of variation for the genetic improvement of other crops such as wheat and rice where a substantial number of chromosome substitution lines are already available.

Technical Abstract: The narrow genetic bases of cotton coupled with low utilization of diverse genetic resources represent two major impediments limiting the genetic improvement of Upland cotton. Here we report for the first time on the development of a set of unique genetic materials by infusing beneficial alleles from three different 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 chromosome substitution lines of G. tomentosum (CS-T), a wild tetraploid species endemic to Hawaii, G. barbadense (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 chromosome substitution lines were dissected into additive genetic effects, homozygous dominance genetic effects and heterozygous dominance genetic effects using an AD statistical model. Five of six CS-B lines and two of six CS-T lines had significant additive genetic effects on lint percentage indicating the respective substituted alien chromosome carried alien alleles with potential to improve lint percentage in Upland cotton. Several of the chromosome substitution lines carried alien alleles with positive additive genetic effects for improved fiber length and strength. 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 percent of 15 significant additive genetic effects of the CS-T lines had potential to improve fiber traits. Results of this research suggested that chromosome substitution provided a genetic approach that could be useful for targeted exploitation of the beneficial alleles from wild and unadapted germplasm and detection of novel alleles associated with important traits in the genetic improvement of Upland cotton.