BIOLOGICAL AND MOLECULAR CHARACTERISTICS OF IRANIAN BIOVARS 2A AND 2T OF RALSTONIA SOLANACEARUM

Abstract

The biological and molecular characteristics of 8 strains of biovars 2A of Ralstonia solanacearum from the Iranian province of Isfahan and of 7 isolates of biovar 2T from the province of Khuzestan were investigated morphologically, physiologically, biochemically, and using pathogenicity tests, BOX-PCR, ERIC-PCR and RFLP. Biovar 2A strains showed irregular, creamy-white and highly fluid colonies with pink center on TZC medium, slow spreading necrosis in hypersensivite reaction (HR) after 48 h, produced melanin in tyrosin test, were less pectolytic and did not utilize ribose and tryptophan. By contrast, biovar 2T strains had small size, less fluid, round and deep red colonies with a thin white margin, did not produce melanin, had a higher pectolytic activity, rapid HR on tobacco leaves after 24 h and utilized ribose and tryptophan. Comparative analysis of the BOX-PCR and ERIC-PCR fingerprint of the 15 strains at the 45% similarity level, revealed two main clusters. comprising all biovar 2A strains (cluster 1) or all biovar 2T strains (cluster 2). RFLP profiles of both biovers did not show any polymorphism. Typically, biovar 2A isolates were more pathogenic and bacterial density was higher in the xylem of all hosts tested. There was no significant difference in biovar 2A and 2T survival in loamy-clay soil, which was up to 186 days under controlled conditions.