Heterosis and Gene Action of Boll Weight and Lint Percentage in High Quality Fiber Property Varieties in Upland Cotton

Twenty F 1 combinations crossed among 5 varieties and strains different in fiber properties according to complete diallel crossing design were used to evaluate the heterosis and gene action of boll weight and lint percentage in high quality fiber property varieties in Upland Cotton in 1998~1999 for two year successively at Nanjing. It was indicated that there existed small interactions with the environmental factors without maternal effects and the additive gene effect was in chief, attaining to 51.2% and 65.4% respectively for boll weight and lint percentage. The dominant effect was also in higher rate, 32.6% and 16.8% respectively. The population mean heterosis of boll weight and lint percentage over the mid parental mean were relatively prominent 13.3% and 3.5% respectively in extreme significance. However, boll weight showed no significantly surpassing parental F 1 heterosis over the better parent based on population mean (2.0%); while the lint percentage expressed significant negative heterosis value (-2.1%). The gene actions were in conformity with the heterosis expression. It was shown clearly that the F 1 combinations crossed between parents with similar performances had relatively high dominant effects and significant positive F 1 surpassing parental heterosis (F 1 heterosis over the better parent); while no F 1 combination crossed between the parents with prominent mutual difference surpassed the higher parent in yield components, which indicated that among those parents with less difference and close relationships, there still existed sufficient genetic variation or certain mechanism for creating variation and achieving greater advances in breeding. Correlation analyses also indicated that there still existed severely undesirable negative correlation between yield and fiber properties as well as the difficulties for their simultaneous improvements.