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Abstract
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Spiroplasma citri is a bacterial pathogen
responsible for the economically important citrus stubborn
disease. Sesame and citrus seeds serve as hosts for both S.
citri and its leafhopper vector Circulifer haematoceps. To
evaluate whether sesame could act as a reservoir for citrusinfecting
strains or not, the genetic diversity among S. citri
strains found in leafhoppers collected in citrus and citrusfree
sesame fields was investigated. Among 26 periwinkle
plants exposed to the collected C. haematoceps leafhoppers,
12 plants developed typical stubborn symptoms. All
symptomatic periwinkles were polymerase chain reaction
positive using S. citri-specific primer pairs targeting the
spiralin and P89 genes. Phylogenetic trees based on spiralin
gene sequence analysis indicated that the novel fieldcollected
strains clustered with those belonging to two
formerly defined S. citri groups (groups 6 and 1). In
addition, our results strongly suggest that group 1 strains
could be transmitted from sesame-infected plants to citrus
trees by C. haematoceps, while group 6 strains may not
infect citrus trees.
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