R. W. Hayes

Effects of chromosome 5sh from Gossypium barbadense L. on flower production in G. hirsutum L.

Cotton (Gossypium spp.) yield is directly determined by mature bolls that developed from squares and flowers. The first four to six weeks of flowering accounts for the majority of lint yield in upland cotton (G. hirsutum L.) for most cultivated areas of the southern USA cotton belt. In this study, we evaluated 13 cotton chromosome substitution lines (CS-B) and their chromosome specific-F2 hybrids, TM-1, 3–79, and six cultivars for the number of flowers produced during the first four weeks of flowering. Results showed that CS-B05sh produced more flowers than TM-1 and 3–79 from 10 July to 5 August. The results suggest that when the short arm of chromosome 5 was substituted from 3–79 (G. barbadense L.) into TM-1 (G. hirsutum) a positive genetic association with flower numbers during this flowering period was exhibited. CS-B05sh had comparable flower numbers with three cultivars, Deltapine 90, Phytogen 355, and Stoneville 474 and more flowers than, Sure Grow 747, Sure Grow 125, and Deltapine 5415. Different patterns for additive and dominance effects on cumulative flowers were observed across weeks of flowering. Dominance effects were more apparent during the early part of the flowering period while additive effects were more apparent towards the end of the flowering period.

Genetic effects of nine Gossypium barbadense L. chromosome substitution lines in top crosses with five elite Upland cotton G. hirsutum L. cultivars

Crosses between Gossypium barbadense L and Gossypium hirsutum L. (Upland cotton) have produced limited success in introgressing fiber quality genes into the latter. Chromosome substitution lines (CSBL) have complete chromosomes or chromosome arms from G. barbadense, line 3-79, substituted for the corresponding chromosome or arms in G. hirsutum in a near isogenic background of TM-1. We top crossed nine CSBL and their parents (TM-1 and 3-79) with five cultivars. Parental lines and their F2 populations were evaluated in four environments for agronomic and fiber quality traits. The CSBL and their F2 hybrids showed wide ranges for both agronomic and fiber traits of economic importance. Genetic analysis showed that additive variances were larger than dominance variances for lint percentage, boll weight, lint yield, fiber length, strength, elongation, micronaire, and yellowness; whereas, dominance variances were larger than additive variances only for uniformity of fiber length and equal for fiber reflectance. For all traits, except boll weight and lint yield, significant additive effects of one or more chromosomes from 3-79 in TM-1 background were greater than the corresponding TM-1 chromosome. In addition, we identified specific chromosomes from G. barbadense (3-79) that carry alleles for improvements in specific fiber quality traits in Upland cotton. Favorable additive effects of individual chromosomes or chromosome segments from 3-79 relative to corresponding chromosomes or chromosomes segments from TM-1 were identified in this study as follows: Lint percentage, chromosome/arms 10, 16-15; longer fibers, chromosome/arms 01, 11sh, 26Lo; more uniform fibers, chromosomes/arms 01, 11sh, 10, 17-11; stronger fibers, chromosome/arms 01, 11sh, 12sh, 26Lo, 17-11; fiber elongation, chromosomes/arms 01, 11sh, 26Lo, 10, 17-11; reduced fiber micronaire, chromosome/arms 01, 12sh, 4-15, 16-15, 17-11; fibers with more reflectance, chromosome/arms 10, 4-15, 16-15, 17-11; fiber with less yellowness, chromosome arms 4-15, 17-11. Based on the present study, we concluded that by using CSBL, favorable fiber quality alleles can be introgressed into Upland cotton, thus greatly improving the breeder’s ability for improvement of Upland cotton for a variety of traits. These data should provide useful genetic information to the cotton breeding industry at large.

Genotypic comparisons of chromosomes 01, 04, and 18 from three tetraploid species of Gossypium in topcrosses with five elite cultivars of G. hirsutum L.

Upland cotton, Gossypium hirsutum L. is the most widely planted cultivated cotton in the United States and the world. The other cultivated tetraploid species G. barbadense L. is planted on considerable less area; however, it produces extra long, strong, and fine fibers which spins into superior yarn. The wild cotton tetraploid species G. tomentosum Nuttall ex Seemann, native to the Hawaiian Archipelago also exhibits traits, such as drought tolerance, that would also be desirable to transfer to Upland cotton. Long-term breeding efforts using whole genome crosses between Upland and these species have not been successful in transferring very many desirable alleles into Upland cotton. Our chromosome substitution lines (CSL) have one chromosome or chromosome arm from an alien species backcrossed into the Upland cotton line,TM-1, via aneuploid technology. Five Upland cultivars were crossed with CS-B01, CS-T01, CS-B04, CS-T04, CS-B18 and CS-T18 and TM-1 the recurrent parent of the CSLs. This provided an opportunity to determine the effects of chromosomes 01, 04, and 18 from the three species in crosses with the five cultivars. Predicted genotypic mean effects of the parents, F2, and F3 generations for eight agronomic and fiber traits of importance were compared. The predicted hybrid mean effects for the three chromosomes from each species were different for several of the traits across cultivars. There was no single chromosome or species that was superior for all traits in crosses. Parental and hybrid lines often differed in the effect of a particular chromosome among the three species. The predicted genotypic mean effects for F2 and F3, with a few exceptions, generally agree with our previous results for additive and dominance genetic effects of these CSL.

Introgression of Gossypium barbadense L. into Upland cotton germplasm RMBUP-C4S1

Gossypium barbadense L. cotton has significantly better fiber quality than Upland cotton (G. hirsutum L.); however, yield and environmental adaptation of G. barbadense is not as wide as Upland. Most cotton in the world is planted to Upland cultivars. Many attempts have been made, over a considerable number of years, to introgress fiber quality alleles from G. barbadense into Upland. However, introgression barriers, primarily in the form of interspecific incompatibility, have limited these traditional approaches. The use of chromosome substitution lines (CSL) as a bridge should provide a more efficient way to introgress alleles from G. barbadense into Upland. We crossed 18 G. barbadense CSL to three cultivars and developed a random mated population. After five cycles of random mating followed by one generation of self-pollination to increase the seed supply, we grew the random mated population and used 139 G. barbadense chromosome specific SSR markers to assess a random sample of 96 plants for introgression. We recovered 121 of 139 marker loci among the 96 plants. The distribution of the G. barbadense alleles ranged from 10 to 28 alleles in each plant. Among the 96 plants we found individual plants with marker loci from 6 to 14 chromosomes or chromosome arms. Identity by descent showed little relatedness among plants and no population structure was indicated by a heat map. Using CSL we were able to develop a mostly Upland random mated population with considerable introgression of G. barbadense alleles which should be useful for breeding.