Isolation and identification of Pseudomonas syringae pv. actinidiae in Shaanxi Province, China

The aim of this study was to evaluate the relationships between the pathogenicity of Pseudomonas syringae pv. actinidiae (Psa) and the geographical origin and cultivars for the main cultivars in the northern area of Qinling, China. Infected kiwifruit branches were collected from 'Hayward', 'Huayou' and 'Hongyang' from Zhouzhi county, Yangling district, and Mei county. Psa was isolated and purified by the conventional tissue method. 16S-23S rDNA ITS sequencing methods were used to analyze the molecular evolution of the pathogens and pathogenicity was also measured. Our results showed the following. 1) A total of 20 Psa strains were obtained by isolation, purification and molecular identification. Colony morphology showed large variation between different geographical origin and cultivar. 2) There were no relationships between pathogenicity of the strains and geographical origin and cultivar. 3) Quantitative and accurate methods of leaf pathogenicity were established based on the software ImageJ 1.50b, and four strong strains were selected. These Psa strains provide a basis for further study on the identification of resistance materials and selection of specific biological pesticides for kiwifruit bacterial canker.