Genetic distance among selected cotton genotypes and its relationship with F2 performance

Knowledge of genetic diversity and relationships among breeding materials has a significant impact on crop improvement. Association between parental divergence and progeny performance has not been well documented in cotton (Gossypium hirsutum L.). The objectives of this study were to estimate genetic diversity among selected cotton genotypes on the basis of simple sequence repeat (SSR) markers, and to investigate the relationship between genetic diversity and F-2-bulk population performance. Five U.S. and four Australian cultivars, and two day-neutral converted lines of G. hirsutum were genotyped by means of 90 SSR primer pairs providing 69 polymorphic marker loci. Genetic distance (GD) between genotypes ranged from 0.06 to 0.34 for the 11 parental genotypes. The highest GD (0.34) was observed between ST474 and the day-neutral converted line B1388. The lowest GD (0.06) was detected between cultivars FM832 and FM975. The GD between day-neutral converted lines and cultivars ranged from 0.26 to 0.34. Among the Australian cultivars, GD ranged from 0.06 to 0.19 while GD among U.S. cultivars varied from 0.10 to 0.22, indicating a narrow genetic base. Significant correlations between agronomic and fiber traits of F-2-bulk populations and GD ranged from negative to positive depending on the traits, genetic background, and environment. On the basis of SSR markers, GD revealed a lack of genetic diversity among all genotypes and it was a poor predictor of overall F-2 performance. However, when genotypes with maximum range of GD were present, it was a better predictor for some traits.