Screening of wild Actinidia germplasms resistant to bacterial canker disease in China

Bacterial canker disease is a serious threat to the development of the kiwifruit industry. Based on the abundant wild Actinidia germplasm resources in China, screening highly resistant germplasms and breeding resistant varieties with great fruit characters is a primary task for the development of the kiwifruit industry. In this paper, we inoculated isolated branches of 82 germplasms of 29 Actinidia species from the national kiwifruit germplasm nursery with Pseudomonas syringae pv. actinidiae. Disease resistance was evaluated based on lesion length, divided into seven categories from highly resistant to highly susceptible. Results showed distinct differences in resistance among the different species, as well as intraspecific resistance differentiation. Among the 82 germplasms, five were highly resistant (6.09%), nine were moderately resistant (10.98%), 18 were lowly resistant (21.95%), 21 were tolerant (25.61%), 11 were lowly susceptible (13.41%), nine were moderately susceptible (10.98%), and nine were highly susceptible (10.98%). The 32 resistant germplasms included six germplasms of A. arguta (Siebold & Zuccarini) Planchon ex Miquel, five germplasms of A. callosa var. discolor C. F. Liang, four germplasms of A. melanandra Franchet, three germplasms of A. callosa var. henryi Maximowicz and A. eriantha Bentham, respectively, two germplasms of A. vitifolia C. Y. Wu, A. styracifolia C. F. Liang, and A. arguta (Siebold & Zuccarini) Planchon ex Miquel var. purpurea (Rehd.) C. F. Liang, respectively, and one germplasm of A. latifolia (Gardner & Champion) Merrill, A. rubricaulis Dunn, A. rufa (Siebold & Zuccarini) Planchon ex Miquel, A. hubeiensis H. M. Sun and R. H. Huang, and A. fulvicoma Hance, respectively. Thus, this study lays a theoretical foundation for the cross-breeding and creation of disease-resistant varieties of kiwifruit.