Genetic diversity of Brenneria nigrifluens strains in North of Iran (margin of Caspian sea)

Abstract

Brenneria nigrifluens, the cause of shallow bark canker of Persian walnut trees (Juglans regia L.), has become fairly widespread in Iran in recent years. It is regarded as a great threat to walnut production. To determine the diversity of B. nigrifluens strains, sixty strains of the causal bacterium were isolated from bark samples of infected walnut trees collected from Mazandaran, Guilan and Golestan provinces and were studied. The physiological and biochemical characteristics, electrophoretic patterns of total cell proteins and rep-PCR generated DNA fingerprints of B. nigrifluens strains were compared. Strains appeared to be more or less similar in phenotypic characteristics. Less than 15% of the strains differed in a few phenotypic features such as the ability in production of H2S from peptone, hydrolysis of esculin, levan production, arginine dehydrolase, nitrate reduction, indol production and methyl red reaction. These differences did not show any special distribution and therefore was not suitable for classifying the strains into distinct groups. The electrophoretic patterns of cell proteins of the strains were different from each other and were only useful for preliminary grouping of the isolates. The groups of strains were differentiated by their rep-PCR fingerprints and on which basis they were placed in six groups in similarity level 95%. Cluster analysis was performed using NTSYSpd software. The results of these studies demonstrated that the populations of B. nigrifluens in North of Iran are genetically heterogeneous. The results can be used in selection of disease management strategies.