Minimum number of genes controlling cotton fiber strength in a backcross population

Textile mills in the USA require strong cotton fiber (Gossypium hirsatum L.) for modern high-speed textile operations. The primary objective of this study was to determine the inheritance of strength descending from FTA 263-20 (FTA). FTA was developed by introgression into G. hirsutum from G. arboreum L., G. thurberii Todaro, and G. barbadense L. Five backcrosses (BCs) into 'Deltapine 16' (DP 16) followed by six BCs into DP 90ne were made. In 2001, three sets of 64 BC6 (F)(:F)(2)(3) progenies were evaluated for strength. Significant variability for F2:F3 strength (F = 2.79), yield, three yield components, and four other fiber traits were detected. From a three replication test, strength gene number(s) estimates ranged from 1.10 to 1.29 and combined over sets was 1.23 genes. Average strength for the three BC5 parents was 10.3% greater than DP 90ne and yield was 16.9% less. Strength was highly correlated with lint percentage, boll weight, seed weight, and 2.5% span length. Gene numbers for these correlated traits ranged from 0.02 for micronaire to 1.04 for yield. A separate study involving the BC5 parents, 'Deltapine 90' (DP 90) and DP 90ne was used to determine the major physical components of strength. Fineness and individual fiber strength had no effect. Short fiber content significantly impacted strength as the three BC5 parents average short fiber was 6.7 versus 8.7% for the DP 90s. The BC5 parents average strength was 11% higher, 240 vs. 219 kN m kg-1, and its yield was 9.0% lower than DP 90ne. Probably a single major gene or closely linked cluster of genes resulted in increased fiber strength.