Comprehensive evaluation of resistance of different strawberry varieties to Xanthomonas fragariae

Xanthomonas fragariae (X. fragariae) is a quarantine pathogen and a tremendous danger to the strawberry industry. Therefore, it's urgent to explore and breed resistant varieties to X. fragariae. In the present study, we evaluated the resistance of 31 strawberry varieties to the X. fragariae YL19-GFP, and finally, 9 moderate resistance (MR) varieties, 18 sensitive (S) varieties, and 4 highly sensitive (HS) varieties were screened. The net photosynthetic rate, chlorophyll a content, jasmonic acid content, salicylic acid content of MR and HS varieties were decreased after inoculated YL19-GFP, while the content of ethylene and abscisic acid were increased. After analyzing the correlation and coefficient of variation between the different indicators of MR and HS varieties, we determined that the disease incidence, disease index, bacteria biomass bacteria fluorescence intensity, ratio of spot area to leaf area, jasmonic acid content, and net photosynthetic rate were suitable indicators for evaluating the strawberry resistance to X. fragariae. Subsequently, we evaluated the above indicator using principal component analysis (PCA) and established the score formula. This work provided a more accurate and comprehensive method to assess the resistance of strawberries to X. fragariae.