Abstract:

【Objective】 Early maturity is fundamental to produce high and stable yield in upland cotton. It is of important practical value to dissect the genetic components and analyze the genotypes of beneficial and unbeneficial loci in crosses using early varieties as parents. 【Method】 Six varieties of different origins were used in an incomplete diallel cross design to evaluate the genetic components in parents and the major locus groups related to earliness in F1s by QTL testing system. 【Result】 The genotypes of major locus groups for growth stages were mainly ++ in the early parents Xinluzao 8 and 10, which have the genetic background of 611-b and King’s cotton, respectively. Each growth stage was significantly shorted in these genotypes. The inheritance of earliness related traits was mainly additive. The growth period had the largest additive value, followed by bloom, seedling and square stages. The additive effects of ++ and -- locus group were equally important in the mid-maturity parent Jing 8891. However, almost all ++ and – locus group were unbeneficial in the late parents Ningzao 1, Sumian 3 and TM-1, with each growth stage delayed. Among all major locus groups in all growth stages, the J=16 locus group had the largest additive values, indicating it can significantly reduce the growth period. The performance of earliness related traits in F1s was affected by both heterozygous and homozygous locus groups, but the growth period was primarily determined by the heterogeneity of the major locus groups. 【Conclusion】 Additive effects of major locus groups for earliness related traits were invariably higher than dominance. The additive effects of major locus groups for square and bloom stages played a predominant role in earliness.

Key words: cotton, early maturity, major locus groups, genetic effects, MLGs × environment interaction