PERFORMANCE OF OBSOLETE AND CURRENT CULTIVARS AND PEE DEE GERMPLASM LINES OF COTTON

Yield and fiber quality comparisons of modern vs. obsolete cultivars and Pee Dee (PD) germplasm lines represent a measure of genetic gain for these traits and can be used to establish a base for estimating future breeding accomplishments. We evaluated 29 commercial cultivars and PD germplasm lines of cotton (Gossypium hirsutum L.), 12 modern and 17 obsolete, in two tests per year for a 3-yr period (1979, 1980, 1981). The soils were a Norfolk fine sandy loam (fine-loamy, siliceous, thermic Typic Kandiudult) and a Norfolk loamy sand at Florence, SC. We sought to determine what genetic improvements the new cultivars and germplasm lines had compared with the obsolete ones. Two modern cultivars, McNair 235 and SC-1 (a PD cultivar with extra fiber strength genes) produced 399 kg ha-1 more lint than the obsolete cultivar, Earlistaple 7, and 522 kg ha-1 more than the PD germplasm Line F. The rate of gain in yield of modern compared with obsolete cultivars and PD germplasm lines was 10.5 and 15.1 kg ha-1 yr-1, respectively. The actual rate of gain in related PD germplasm lines was 20.6 kg ha-1 yr-1. A regression analysis of the average yields in South Carolina and the South Atlantic states from 1961 through 1987 showed that yields have significantly increased at the rate of 8.0 and 9.4 kg ha-1 yr-1, respectively. These data show that cotton breeders have made continuous progress in improving lint yield, without sacrificing fiber quality. This trend can be expected to continue. Simultaneous improvements in lint yield and fiber strength can be expected if emphasized in breeding programs.