Bull. Spec. CORESTA Congress, Lisbon, 2000, p. 124, P4

Diversity of Ralstonia solanacearum in the Southeastern United States

Clemson University, Dept. of Plant Pathology and Physiology, Pee Dee REC, Florence, SC, USA.
Bacterial (Granville) wilt, caused by Ralstonia solanacearum , is a major disease of tobacco in both North and South Carolina. In contrast, Granville wilt rarely occurs on tobacco in Georgia, Florida and Virginia. This difference was noted over fifty years ago and, today, it is still not understood. Understanding the population structure and dynamics of R. solanacearum , the impacts of host genotype and environmental and cultural practices on the pathogen will facilitate development of improved management strategies. Isolates of R. solanacearum from tomato and tobacco were collected from Florida, Georgia, and North and South Carolina. All isolates were identified as race 1, biovar 1. A PCR-based genomic DNA fingerprinting procedure, rep-PCR, was used to generate genomic fingerprints that were used to assess the genetic diversity of the R. solanacearum isolates. Bands were scored as present or absent and converted to distances. Principle component analysis (PCA) of the distance matrices grouped the Carolinian isolates apart from most other isolates. R. solanacearum isolates from tomato clustered as a function of geographic region. Tobacco isolates from Georgia grouped independently of South Carolina isolates. A limited degree of clustering by county was also noted for the South Carolina isolates. Two isolates from tobacco and two from tomato from both Georgia and South Carolina, which showed the greatest degree of diversity in the analysis described above, were evaluated for aggressiveness on a susceptible cultivar of tobacco, K326, under controlled environment conditions. The relationship between the observed clusters from PCA and the severity of wilt caused by each of the representative isolates will be presented.