Study of Walnut Black Spot (Anthracnose) Disease in Zanjan Province and Evaluation of Partial Resistance of Some Local and Exotic Walnut Genotypes Against the Disease

Walnut tree is one of the most important orchard and jungle trees in Iran. It's world cultivation is growing up due to its plentiful uses. Meanwhile, some pests and diseases are known as the major reasons of restriction in walnut cultivation. Among walnut diseases, anthracnose is the most destructive in Iran. In this study, the main area of walnut cultivation in Zanjan were surveyed, walnut's infected organs (sprouts, leaves and fruits) were sampled and the disease agent was isolated and identified using ordinary plant pathological methods. The results showed that Ophiognomonia leptostyla (Fr.) Sogonov contribute to the walnut anthracnose disease, and it is permanently scattered in all Zanjan walnut orchards. It's damage varies between15% to 67% in different regions. Our study on Telemorph and Anamorph phases of the fungus showed that there are no significant differences between isolates collected from Zanjan and those from other provinces in vicinity. Meantime, the results showed that the majority of the collected isolates were Heterothal. Study on partial resistance of three Iranian local genotypes (Z53, Z63 and 60) and six exotic cultivars (Sere, Lara, Franket, Pedro, RDM and B21) showed that local genotypes were more susceptible to walnut anthracnose in comparison to exotic varieties. Although none of the varieties and genotypes was totally resistant, in comparison to introduced interior superior genotypes, exotic varieties of Persian walnut were by far in better condition against anthracnose.