Gossypium barbadense L. line 3-79 is lower in yield, has smaller bolls and longer, finer, and stronger fibers than upland cotton G. hirsutum L. Thirteen chromosome substitution (CS-B) lines with individual 3-79 chromosomes or arms substituted into TM-1, G. hirsutum, were top crossed with five elite cultivars and additive and dominance effects for the yield components, lint percentage, boll weight, seed cotton yield, and lint yield, were measured over four environments. Additive effects were greater than dominance effects for all traits. CS-B lines had smaller additive and homozygous dominance effects than the cultivars for most traits. Many CS-B lines had negative additive effects; however, chromosome substituted arms 22sh and 22Lo showed additive effects for lint yield that were significantly greater than homologous chromosome arms in TM-1. Hybrids of DP90 3 CS-B15sh, ST 474 3 CS-B17, and FM 966 3 CS-B02 had positive dominance effects for lint yield significantly greater than the homologous chromosomes in TM-1. Several chromosomes or arms were associated with significant negative additive or dominance effects. These data provide a valuable baseline on yield components for the utility of these CS-B lines in commercial breeding programs. When individual chromosomes or chromosome arms, via CS-B lines, are used in crosses with cultivars, alleles for yield components on specific G. barbadense chromosomes were uncovered that showed positive interactions with alleles in elite germplasm.

Molecular markers closely linked to genes that confer a high level of resistance to root-knot nematode (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood] in cotton (Gossypium hirsutum L.) germplasm derived from Auburn 623 RNR would greatly facilitate cotton breeding programs. Our objectives were to identify simple sequence repeat (SSR) markers linked to RKN resistance quantitative trait loci (QTL) and map these markers to specific chromosomes. We developed three recombinant inbred line (RIL) populations by single seed descent from the crosses of RKN-resistant parents M-240 RNR (M240), developed from the Auburn 623 RNR source, moderately resistant Clevewilt 6 (CLW6), one of the parents of Auburn 623 RNR, and susceptible parent Stoneville 213 (ST213). These crosses were CLW6 × ST213, M240 × CLW6, and M240 × ST213. RILs from these populations were grown under greenhouse conditions, inoculated with RKN eggs, scored for root gall index, eggs plant(-1), and eggs g(-1) root. Plants were also genotyped with SSR markers. Results indicated that a minimum of two major genes were involved in the RKN resistance of M240. One gene was localized to chromosome 11 and linked to the marker CIR 316-201. This CIR 316-201 allele was also present in CLW6 but not in Mexico Wild (MW) (PI593649), both of which are parents of Auburn 623 RNR. A second RKN resistance gene was localized to the short arm of chromosome 14 and was linked to the SSR markers BNL3545-118 and BNL3661-185. These two marker alleles were not present in CLW6 but were present in MW. Our data also suggest that the chromosome 11 resistance QTL primarily affects root galling while the QTL on chromosome 14 mediates reduced RKN egg production. The SSRs identified in this study should be useful to select plants with high levels of RKN resistance in segregating populations derived from Auburn 623 RNR.

Thirteen chromosome substitution lines (CS‐B) lines with individual 3‐79 Gossypium barbadense L. chromosome or arms substituted into TM‐1, G. hirsutum L., were crossed with five Upland cultivars and additive and dominance effects for fiber micronaire, elongation, length, and strength were measured over four environments. Additive genetic effects were considerably larger than dominance or environmental interaction effects. Fiber strength of 3‐79 and FM966 were 282 and 240 kN m kg−1, respectively. FM966 had greater additive effects for fiber length (1.13 mm) and strength (12.90 kN m kg−1) than any CS‐B line; however, CS‐B25 had the greatest additive effects (8.97 kN m kg−1) for strength among CS‐B lines. The greatest negative additive effect for fiber length was −1.29 mm (CS‐B22sh). Although several CS‐B lines had negative additive effects on strength, none was more negative than TM‐1 (−5.31 kN m kg−1). CS‐B02 and CS‐B25 had additive effects on strength of 2.36 and 8.97 kN m kg−1 SG747 had the greatest negative additive effect (−12.13 kN m kg−1) for strength among cultivars and CS‐B lines. CS‐B07 and CS‐B18 had negative additive effects for fiber strength but had significant and positive dominance effects with FM966. When individual CS‐B lines were crossed with elite cultivars beneficial alleles for fiber properties were uncovered on specific chromosomes or chromosome arms that should aid introgression of alleles from 3‐79 into Upland.

RMUP‐C5 (Random Mated Upland Population Cycle 5) (Reg. No. GP‐893, PI 652942) is a unique random mated germplasm population of Upland cotton (Gossypium hirsutum L.) involving six cycles of random mating beginning with an 11 parent half diallel. This germplasm was developed through cooperative research by the USDA‐ARS, Mississippi Agricultural and Forestry Experiment Station, North Carolina State Agricultural Experiment Station, and Cotton Incorporated. Parents used in development represented nonrelated or distantly related cultivars or breeding lines from across the U.S. Cotton Belt. The bulked pollen method of pollination was used in the development, and there were six cycles of random mating, with intercrossing of the F1 considered cycle zero. Selfed seed of C5S1 has been released. Changes in correlations between traits among parents, C0, and C5 cycles show that after random mating, the C5 population has recombinations that should be useful for selection and cultivar development. Because this germplasm represents random mating among 11 very diverse breeding programs and includes parents from the major seed breeding companies, this population should be of value to breeders across the U.S. Cotton Belt.

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-F 2 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 flower-