Comparison of Methods for Identification of Resistance to Pear Fire Blight and Screening of Resistant Rootstock Germplasm

Taking container seedling of Pyrus betulaefolia Bunge as test material, three kinds of artificial inoculation methods were used, namely dipping method, needle inoculation method and spray method, to investigate the time of incidence, incidence rate and disease index, compare the inoculation effect of Pyrus betulaefolia Bunge under different inoculation methods, screen the suitable method of pear fire blight inoculation and optimize the inoculum concentration for the best inoculation method, in order to screen the accurate and rapid identification method of pear fire blight and understand the resistance level of different rootstock germplasm to pear fire blight.The results showed that the incidence rate and disease index of the three inoculation methods were as follows, seedling dipping method＞seedling spraying method＞seedling needling method, and the shortest days for investigating the susceptibility and resistance were 7-9 days, 12-33 days and 33-38 days.The seedling dipping method had the fastest incidence rate, good uniformity and easy operation, which could effectively shorten the inoculation time and improve the inoculation efficiency.When the OD₆₀₀ value of the bacterial solution was 1.2,the incidence rate and disease index were stable over time with relatively small fluctuations, which could be used as a suitable inoculation concentration for the seedling dipping method.On this basis, five collections of Pyrus betulaefolia Bunge germplasm from different sources were identified by inoculation against fire blight at the seedling stage.The results showed that all the five germplasm were susceptible or highly susceptible to the disease, and the Pyrus betulaefolia Bunge rootstock resources of disease-resistant need to be further explored.