Study on shallow bark canker disease of walnut in Kerman province

Walnut is one of the important nuts with a high economic value. Shallow bark canker, caused by Brenneria nigrifluens, is one of the most dangerous diseases of the walnut trees. Early detection of the causal agent has an important role in preventing economic and irreparable losses caused by this disease. In this study, 57 bacterial strains were isolated from walnut trees with the typical lesions of the shallow bark cankers from different regions of Kerman province. These isolates were divided into two groups, based on phenotypic and biochemical characteristics and then, amplification product of the expected size (255 bp) was obtained with genomic DNA using specific pair primers in B. nigrifluens isolates.Pathogenicities of the isolates were assessed on immature walnut fruits. To identify the causal and the associated bacteria molecularly, a part of 16s rDNA gene sequence was analyzed. Results showed that B. nigrifluens with a significant genetic diversity spread over different regions of Kerman province. In addition, the genus Gibbsiella can probably contribute to the increase of the disease severity, which requires further studies.