|Institution:||University of Georgia|
|Department:||Plant Breeding, Genetics and Genomics|
|Full text PDF:||http://purl.galileo.usg.edu/uga_etd/kumar_pawan_201212_phd|
Germplasm lines derived through interspecific introgressions are important resource for plant breeders targeting novel alleles from wild or unadapted relatives to improve elite germplasm. Among the four Gossypium species domesticated for their cotton fibers, cultivated form of Gossypium hirsutum L. commonly called Upland cotton accounts for 96% of global cotton fiber production. The other three cultivated species, including Gossypium barbadense L., Gossypium arboreum L., and Gossypium herbaceum L., have been replaced by Upland cotton due its high yield potential and broader environmental adaptation. In Upland cotton historical records suggested that several obsolete germplasm lines with excellent fiber quality may have been derived via interspecific introgression; however the effective utilization of such lines in marker assisted breeding rests on the ability to target and exploit segments harboring favorable alleles. The objective of this study is to identify and evaluate the effects of alien chromosomal segments in two G. barbadense introgressed lines, Sealand 542 & Sealand 883. F2 mapping populations were developed by crossing the Sealand lines with Upland cotton lines representing major types of genetic backgrounds of the US cotton. We used 1170 SSR markers to identify locations of the putative introgressed segments. Our results show that a total of 22 putative introgressions were detected including 12 introgressions on 7 chromosomes in the Sealand 542 genome and 10 introgressions on 5 chromosomes in the Sealand 883 genome. QTL analysis revealed that a number of the identified introgressed regions harbored positive alleles for fiber quality traits. Efficacy of these introgressed alleles were tested over two generations (F2:3 and F2:4) across multiple genetic backgrounds and our results show that several of the introgressed fiber quality alleles from G. barbadense were consistently detected over generations as well as across genetic backgrounds. However the percent phenotypic variation explained by the introgressed QTLs varied across genetic backgrounds suggesting epistatic interaction with the genetic background in which these were present. Prospects of utilizing Sealand lines in Upland cotton breeding programs and germplasm improvement are also discussed.