Diallel analysis of root-knot nematode resistance based on galling index in upland cotton.

摘要

The southern root-knot nematode (RKN) [(Meloidogyne incognita (Kofoid and White) Chitwood) RKN] is one of the most destructive pests in the Cotton Belt of the U.S. Developing and employing resistant cultivars is the most economical and efficient method for RKN management. This greenhouse investigation was conducted to understand the quantitative genetic basis of RKN resistance in the major RKN resistance sources using a nine-parent diallel analysis based on improved RKN evaluation techniques. The selected genotypes consisted of three 'Aubrun 623 RNR' (here RNR=Root-knot Nematode Resistance)-derived resistant lines, one moderately resistant cultivar 'Acala Nem-X', and five susceptible cultivars. Comparison between F1 and their parents in galling index revealed that the RKN resistance is partially dominant. The general combining ability was more important than the specific combining ability for RKN resistance. The estimates for broad-sense and narrow-sense heritabilities on galling index were 0.82 and 0.65, respectively, indicating that RKN resistance in the Auburn and Nem-X resistance sources is largely controlled by genetic and additive effects. The minimum number of genes for RKN resistance was estimated to be two. Therefore, under reliable and uniform RKN inoculation and infestation conditions, single plant selection should be efficient in transferring Auburn RKN resistance into elite genetic backgrounds..