Characteristics of bacteria isolated from soil and roots of fruit trees

A total of 142 strains of aerobic bacteria were isolated from soil (43 strains) and roots of peach (51 strains) and apple (48 strains) trees using YA agar medium (egg-albumin agar medium containing yeast extract). On the basis of the morphological, physiological, and chemotaxonomic characteristics, these strains were divided into 6 groups. The strains of group 1 were assigned to the genus Agrobacterium on the basis of the presence of flagella, ubiquinone system and cellular fatty acid composition. Of 70 strains of this group, 34 and 29 strains were isolated from the roots of peach and apple trees, respectively. Forty percent of the isolates of Agrobacterium exhibited antagonism (in vitro) against the fungus Rosellinia necatrix. Of the remaining groups, the strains of groups 2 and 3 were assigned to the genus Pseudomonas and Xanthomonas, respectively. Strains of group 2 were isolated from only the roots and those of group 3 from only soil. Gram-positive (group 5) and spore-forming (group 6) bacteria were isolated from mainly soil.