Diallel Analysis of Ekangmian 9 and Other Cotton Varieties Apparently Resistant to Fusarium Wilt and Tolerant to Verticillium Wilt

Background: Fusarium wilt and Verticillium wilt of cotton are two important diseases adversely affecting cotton yield in China. Thus, disease-resistant cultivars are urgently needed to ensure stable cotton production. In this study, Ekangmian 9 and six other cotton varieties resistant to Fusarium wilt and differentially resistant or tolerant to Verticillium wilt were used as parents in diallel crosses. The main agronomic and fiber quality traits of the offspring were studied regarding genetic variance components, genetic effects, correlations, and competitive advantages. This study may be relevant for enhancing the selection of parents for hybridizations and for improving the selection of offspring and the application of heterosis. Results: Most of the examined traits were controlled by additive genetic effects. Additionally, P2 (Ekangmian 9 or Jing 55173), P5 (CCRI 23), and P6 (Shiyuan 321) were useful for improving the yield traits of their offspring. Moreover, P2 also significantly decreased the incidence of Verticillium wilt, while not adversely affecting fiber quality traits. The P1 × P2, P2 × P5, and P4 × P6 combinations were associated with mid-parent heterosis and competitive advantages. Correlation analyses revealed that increases in lint yield were mainly related to decreases in the diseased plant rate and infection index during the flowering period as well as increases in seed cotton yield. Conclusion: Of the analyzed cotton varieties, P2 (Ekangmian 9 or Jing 55173) may be the most appropriate parent for improving offspring characteristics, especially yield traits. In this study, P2 was included in four superior combinations (i.e., P1 × P2, P2 × P5, P2 × P4, and P2 × P6). Furthermore, Ekangmian 9 has been used as a parent in hybridizations that have resulted in a series of new high-yielding and high-quality cotton varieties including CCRI63 and CCRI66. Key words: Ekangmian 9, Breeding of Verticillium wilt-resistant cultivars, Diallel analysis, Genetic effects, Heterosis, Correlation analysis