ABSTRACT

Average cotton yield per hectare in China has been increased at a rate of 16.14 kg·ha^-1year^-1 since 1950, to which cotton breeding has made tremendous contributions. The objectives of the present study were to compare the performance of selected cotton cultivars released since the 1950s in order to estimate the genetic gain for lint yield, fiber quality, and other major agronomic traits. The results indicated that the yield gain due to cultivar improvement was 8.75 kg·ha^-1year^-1 for spring-sow cultivars grown in the Yellow River Valley, 8.16 kg·ha^-1year^-1 for spring-sow cultivars grown in the Yangtze River Valley, and 7.92 kg·ha^-1year^-1 for short season cultivars, which accounted for 46-54% of annual yield increase. The increase in yield potential in later released cultivars was attributed to the increase in number of bolls per plant and lint percentage. Furthermore, modern cultivars had improved fiber strength, earliness, and resistance to Fusarium wilt and Verticillium wilt diseases. However, they were significantly taller with slightly smaller boll, smaller seed, and coarse fiber. No significant improvement in fiber length was detected.