PLANT AGE AND STRAIN OF RALSTONIA SOLANACEARUM AFFECT THE EXPRESSION OF RESISTANCE OF TOBACCO CULTIVARS TO GRANVILLE WILT

Granville wilt (GW), a devastating disease of tobacco, is best managed through a combination of rotation with nonhost crops, soil fumigation, and implementation of resistant cultivars. Resistance incorporated from Nicotiana tabacum T.I.448A has been the source of resistance against GW in the United States. Resistance is hard to select for and deployment is difficult as location specificity exists for different races and biovars of GW worldwide. Various methods of determining cultivar resistance to GW in tobacco have been utilized with the use of plants of different ages and various strains of Ralstonia solanacearum. In this study we modified a laboratory method previously developed for determining races of Phytophthora nicotianae and examined its effectiveness to evaluate cultivars for resistance to GW. Two root injury methods, root abrasion and root wounding, were tested with 16 strains collected from tobacco fields in North Carolina in 2008. Four cultivars were used: K 346, SP 168, NC 71, and K 326. Res...