Development and Characterization of Chromosome Substitution and Chromosome Segment Substitution Lines in Cotton (Gossypium Spp.).

Abstract

Genetic improvements of Upland cotton (Gossypium hirsutum L.) must be continuous if the crop is to remain biologically and economically viable. The notoriously low genetic diversity found among cultivated Upland cottons constrains opportunities for improvements by breeding based on conventional elite-by-elite crosses. Fortunately, each related wild AD-genome species harbors about 80,000 genes and so introgression of a wild species genome significantly increases genetic variation available among Upland cottons. Most genes from a non-domesticated donor species would expectedly be agriculturally neutral or deleterious, thus, for multi-genic traits, it would expectedly be virtually impossible to discern the presence of a beneficial allele or gene in a donor genome until that DNA variant is selectively integrated into an Upland cotton genetic background. In this study, chromosome substitution lines (CSLs) were genetically characterized and phenotypically characterized for fiber quality and Fusarium oxysporum f.sp. vasinfectum Race 4 resistance. To potentially complement CSL-based coverage of the G. mustelinum genome, a library of newly develop chromosome segment substitution lines (CSSLs) was initiated. A total of 58 chromosome substitution lines (CSLs) representing three species (G. mustelinum, G. tomentosum, G. barbadense) introgressed into G. hirsutum (Texas Marker-1, TM1) were grown in a replicated trial and used for fiber quality analysis. Advanced Fiber Information System (AFIS) and High-Volume Instrument (HVI) were used to measure fiber quality. Several CSLs were found to have improved fiber quality over the recurrent parent, TM1. The largest positive change in fiber quality among CSLs occurred in T16 with significantly lower short fiber content. In contrast, B16 increased short fiber content. CSLs and traditional elite breeding materials were used to search for FOV4 resistance. Genetic variance analysis showed the CSLs contributed more variance than the traditional elite breeding material when disease severity ratings of the roots and seedling mortality death were used to estimate resistance. Two mechanisms of resistance appear to be responsible for the phenotypes. Previous efforts to establish G. mustelinum CSSLs were extended from the BC4F1 to the BC5S3 generation. Marker-assisted screening of BC5S2 individuals identified twenty-five with homozygous introgressions that encompass ~800 cM of the G. mustelinum genome.