ABSTRACT

The Regional High Quality Variety Tests (RHQ) were initiated in 1964 with objectives of broadening the cotton genetic base, promoting open exchange of germplasm and producing varieties with better fiber quality. The specific objective in this report is to evaluate breeding progress for producing cottons with better combinations of yield and fiber quality. The RHQ was conducted on an average of 9.2 states/year for the years 1964 to 1999. The nine states covered the Mid South from the Carolinas to East Texas. The variation for yield, yield components, and fiber traits was partitioned into variations due to states (E), genetic entries (G), and their GXE interaction. About 80% of the total variance for yield, and colorimeter Rd and +b was associated with E. For the yield components, lint percentage, and boll and seed weight, 53% was associated with E, 29% with G, and 18% with GXE. The estimates of fiber length, upper half mean, 2.5% and 50% span length and uniformity averaged 52% for E, 22% for G, and 25% for GXE. Strength estimates were the most heritable with 44% of its total variance be-ing associated with G. Micronaire and its component, maturity, averaged 63% for E and 16% for G.

The test average yield increased at a rate of 2.9 lb/acre/year (Prob. = 0.13) for the 36-year period. Lint percentage increased and boll and seed weight decreased (Prob. < 0.001). The results for fiber length varied with slight increases in 50% span length and uniformity, and decreases in upper half mean and 2.5% span length. In general, little progress for fiber length was observed. Breeders did make progress in improving stelometer and HVI strength (Prob. = 0.001). Expressed as a percent of the mean, the increase was 0.6 and 0.3% per year. In these tests, no trend for micronaire was detected.

Six traits showed significant (Prob. <0.05) changes in their association with yield, lint percentage became more positively correlated with yield and boll weight and seed weight became more negatively associated with yield. Increasing fiber length and HVI strength became more negatively associated with yield. The trait whose association with yield changed the most was micronaire. For the first 18 years, there was no association of yield on micronaire, b = 0.0. For the last 18 years, the average regression of yield on micronaire was 147 lb/acre. If a high yielding cotton with micronaire of 5.2 was reduced to 4.2, one expects yield to be decreased 147 lb/acre.

Analysis of these 36-years of breeding for fiber quality show that small increases in yield and fiber strength have occurred. It also shows that increasing yield still has a higher priority in breeding than increasing fiber quality and that increases in yield have been mainly due to increases in lint percentage and micronaire.