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Molecular Diversity of Ralstonia solanacearum Isolated from Ginger in Hawaii

First and eighth authors: Hawaii Agriculture Research Center, Aiea 96701; first author: Department of Molecular Biosciences and Biosystems Engineering, University of Hawaii, Honolulu 96822; second and sixth authors: Department of Plant and Environmental Protection Sciences, University of Hawaii; fifth author: Department of Tropical Plant and Soil Sciences, University of Hawaii; and third, fourth, and seventh authors: U.S. Department of Agriculture-Agricultural Research Service, Pacific Basin Agricultural Research Center, Hilo, HI 96720

The genetic diversity of Ralstonia solanacearum strains isolated from ginger (Zingiber officinale) growing on the island of Hawaii was determined by analysis of amplified fragment length polymorphisms (AFLPs). Initially 28 strains of R. solanacearum collected from five host plant species worldwide were analyzed by AFLP. A second analysis was conducted on 55 R. solanacearum strains collected from three ginger farms along the Hamakua Coast of Hawaii, the principle area of ginger cultivation in the state. From the initial analysis, R. solanacearum strains from ginger in Hawaii showed a high degree of similarity at 0.853. In contrast, the average genetic similarity between R. solanacearum strains from heliconia and ginger was only 0.165, and strains from ginger showed little similarity with strains from all other hosts. The second analysis of 55 strains from ginger on different Hawaiian farms confirmed that they were distinct from race 1 strains from tomato. Strains from ginger also showed greater diversity among themselves in the second analysis, and the greatest diversity occurred among strains from a farm where ginger is frequently imported and maintained. Our results provide evidence that R. solanacearum strains from ginger in Hawaii are genetically distinct from local strains from tomato (race 1) and heliconia (race 2).

Additional keyword: bacterial wilt, phylogeny.