Inheritance of resistance to Pseudomonas syringae pv. actinidiae and genetic correlations with fruit characters in a diploid Actinidia chinensis (kiwifruit) population

Bacterial canker of kiwifruit, caused by a virulent strain of Pseudomonas syringae pv. actinidiae (Psa), has resulted in serious damage to kiwifruit industry worldwide. The variability and inheritance of resistance to Psa and fruit characters in a disconnected factorial mating population of diploid Actinidia chinensis Planch were investigated. Significant variation in all characters was found, and this appeared to be under polygenic control. Results indicated the extent and nature of genetic variation in Psa resistance available in our breeding gene pool. Estimates of narrow-sense heritability were moderate-high to high for Psa resistance, fruit weight, dry matter content (DM) and soluble solids contents (SSC), but low for fruit number per vine. The moderate-high heritability for Psa resistance indicated a genetic control of the observed variation, and selection for Psa resistance could be possible. Psa resistance had a high negative genetic correlation with fruit number per vine, but a moderate positive correlation with fruit weight, DM and SSC. The results implied that yield penalty of Psa resistance might exist in kiwifruit. Thus, selection strategies based on Psa resistance need to take account of its negative correlation with fruit number per vine. Male and female parents useful for improving Psa resistance and fruit characters simultaneously were identified. Two full-sib families were outstanding, as they combined high degrees of resistance to Psa with high yield components and reasonable amounts of DM and SSC.