Periwinkle Wilt Bacterium: Axenic Culture, Pathogenicity, and Relationships to Other Gram-Negative, Xylem-Inhabiting Bacteria

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Abstract
The Gram-negative, xylem-inhabiting bacterium associated with periwinkle wilt (PW) disease [on Catharanthus roseus] was consistently isolated on the PW, SC and BC-YE media from PW-diseased periwinkle, but not from healthy periwinkle. Colonies of the bacterium were circular with entire margins, convex, opalescent-white and reached 0.4-1.0 min in diameter after 2-3 wk at 28.degree. C. The periwinkle bacterium incited typical PW symptoms during July and Aug. in periwinkle inoculated during the previous fall and winter. The periwinkle bacterium and the bacterium that causes Pierce''s disease (PD) of grapevine were pathologically distinct. The periwinkle bacterium infected grapevine, but no symptoms developed which could be attributed solely to the infection. The PD bacterium incited slight chlorosis in periwinkle, but did not incite typical PW symptoms. The ultrastructure and morphology of the periwinkle bacterium in culture, inoculated periwinkle and a sharpshooter vector, Homalodisca coagulata, were similar. The periwinkle bacterium was distinguishable from similar Gram-negative, xylem-inhabiting bacteria associated with PD, phony disease of peach (PDP) and plum leaf scald (PLS), in that it grew readily on the PW, SC and BC-YE media, but not on PD2 medium. In an enzyme-linked immunosorbent assay (ELISA), the periwinkle bacterium was closely related to the PDP and PLS bacterium.