Chromosomal and pTi genotypes of agrobacterium strains isolated from Populus tumors in two nurseries

Abstract Agrobacterium tumefaciens strains isolated from aspen tumors have been characterized in order to study Ti plasmid stability in different chromosomal backgrounds under natural conditions. Chromosomal and pTi genotypes were characterized by DNA-DNA hybridization. Single tumors contained one to four strains of A. tumefaciens as characterized by their chromosomal genotypes and one or two different nopaline-type pTi genotypes. Genotypes of pTi were associated with identical chromosomal backgrounds in different tree nurseries, suggesting that pTi plasmids are stably maintained in the small set of strains causing the present aspen crown gall outbreaks.