Poster Session: New and Emerging Diseases - Bacteria

423-P

Casuarina equisetifolia decline in Guam linked to colonization of woody tissues by bacteria.
R. L. SCHLUB (1), R. Kubota (2), A. M. Alvarez (2)
(1) University of Guam, Mangilao, Guam, U.S.A.; (2) University of Hawaii, Honolulu, HI, U.S.A.

Ironwood trees (Casuarina equisetifolia) on the island of Guam are in decline due to a combination of biotic and abiotic factors. Bacteria associated with wet-wood and vascular wilt are emerging as significant biotic factors in addition to those previously established, which include the wood-rotting fungus, Ganoderma australe species complex, and termites. Symptoms include thinning of foliage and dark discoloration of the tree’s central core, which are associated with the onset of ironwood tree decline. Ralstonia solanacearum and two other bacterial species were consistently recovered in mixed culture when initial isolations were made from discolored wood tissue and from droplets of bacterial ooze, which often form on stem cross-sections of declined trees. R. solanacearum and one of the unidentified bacterial species were translocated through xylem vessels of young tomato and C. equisetifolia plants following wound inoculation with the bacterial mixture that oozed from infected wood. Confirmation of R. solanacearum was based on cultural characteristics, Agdia immunostrip SK 33900/0025 and loop-mediated isothermal amplification data. Healthy tissues were negative for both the immunodiagnostic and the LAMP assays. This study presents the first evidence that bacteria are involved in the ironwood decline disease complex.