NECESSITY OF EVALUATION OF DIFFERENT WALNUT ORGANS FOR SELECTION OF BLIGHT RESISTANT CULTIVARS

Planting walnut cultivars resistant to blight caused by Xanthomonas arboricola pv. juglandis is one of the most significant management methods. Considering susceptibility of all walnut green organs to this disease, the aim of this research was to evaluate the relative susceptibility of leaf, unripe and ripe organs of Jamal, Damavand and Z76 local cultivars and Pedro, Serr, Chandler, Franquette and Hartley commercial cultivars to blight in order to establish a suitable evaluation procedure. The causal agent was isolated from blighted fruit samples collected from Qazvin, Zanjan, Orumie and Karaj orchards and after identification, mixture of four isolates was used as inoculum. One-year-old grafted seedlings were evaluated for leaf susceptibility in glasshouse condition. Ripe and unripen fruits were examined in orchard and laboratory, respectively. Based on the result, the resistance of different organs was different in various cultivars. Owing to the lack of any correlation between fruit and leaf susceptibilities, evaluation of both organs in resistance evaluations is necessary.