Discovery of a new plant-pathogenic spiroplasma.

To study natural transmission of Spiroplasma citri in the Mediterranean area, periwinkles (Vinca rosea L.) were exposed to natural infection in several locations during the summer of 1983. Detection of S. citri in the periwinkles was assayed by ELISA and culture of the organisms. Some of the periwinkles developed yellows disease symptoms; they contained helical organisms in their sieve tubes, as determined by electron microscopy. A spiroplasma could be cultured from them, but their ELISA reaction for S. citri detection was negative. These results suggested that a spiroplasma different from S. citri had been discovered. The apparently new spiroplasma (P40) was examined for serological relationships with other spiroplasmas by metabolism inhibition and deformation tests. Spiroplasma P40 was found to have relatedness only to Group I spiroplasmas. Healthy periwinkles graft inoculated with shoots of the initial symptomatic periwinkle showed yellows symptoms 3 months after inoculation. Extracts of the initial and the graft-inoculated periwinkles gave positive ELISA reactions with anti-P40 IgG.