Comparative proteomic analysis of apple branches susceptible and resistant to ring rot disease

Ring rot disease, caused by the Botryosphaeria berengeriana f. sp. piricola pathogen, is a destructive disease for apple production. To gain further understanding about the defense mechanisms of apple branches against ring rot disease, a comparative proteomic analysis was conducted in our study. We selected two different host responses to B. berengeriana f.sp. piricola infection or challenge, and compared the different proteomes of susceptible and resistant apple branches that had or had not been inoculated with the pathogen. By using 2-DE and MALDI-TOF-TOF MS analysis, 27 differentially expressed proteins were identified in two inoculation assays. According to their function, the proteins were categorized into five classes. In total, according to these two inoculation assays, there were six differentially expressed defense-related proteins identified in the bark of susceptible and resistant hosts, including Mal d1, ASR, and SAMS, which may play key roles for the resistance mechanisms of each host against ring rot disease. We speculated that the only up-regulation of the ASR protein and the dramatic decrease of SAMS in the resistant host may be related to its better disease resistance. In addition, a total of 10 proteins exhibited opposite expression patterns in the bark of susceptible and resistant branches, and they may also be related to the different disease resistances of the two hosts. Due to the complexity of antifungal mechanisms of apple branch hosts against ring rot disease, to obtain more valuable insights about the interaction between the apple host and B. berengeriana f. sp. piricola pathogen, many further investigations will be conducted.