Reaction of some Walnut Cultivars and Genotypes to Bacterial Blight Disease Caused by Xanthomonas arboricola pv. Juglandis in Greenhouse

Response of new local walnut cultivars Jamal and Damavand, a superior local genotype Z67 and commercial cultivars Pedro, Serr, Chandler, Franquette and Hartley to bacterial blight disease was evaluated in 2009. Leaf rejection, leaf-to-shoot extension of blight, direct shoot infection and correlation between blight resistance levels and vegetative growth were studied. Mixed suspension of the most pathogenic strains of the pathogen collected from four locations was used as inoculum. One-year-old grafted seedlings were evaluated for leaf susceptibility in greenhouse using leaf spray method. Based on the results, Serr, Damavand, Jamal and Z67 were relatively susceptible and Pedro, Chandler, Franquette and Hartley were relatively resistant. Adjoining leaf spots and early leaf abscission was frequent in Jamal and Serr. Results of vegetative growth measurement indicated that Pedro and Chandler were slow growing while Serr and Hartley, fast growing and a correlation was observed between vegetative growth and blight susceptibility. With respect to blight resistance, cultivation of Chandler, Hartley and Pedro is all areas of Iran and local cultivars in semi-arid areas can be recommended.