OCCURRENCE AND MOLECULAR DETECTION OF SPIROPLASMA CITRI IN CARROTS AND ITS INSECT VECTOR CIRCULIFER TENELLUS IN MEXICO
K.D. Swisher, R. Velásquez-Valle, J. Mena-Covarrubias, J.E. Munyaneza
In 2014, carrot plants in Zacatecas, Mexico, were found with yellow, brown, or purple-colored leaves, which were occasionally smaller and rolled. Roots of these affected plants were hairy, deformed, and small. Molecular diagnostics failed to detect phytoplasmas in these samples, but identified Spiroplasma citri in 58 and 94% of the samples using PCR targeting the spiralin and adhesion-related protein 1 (arp1) genes, respectively. Sequence analysis confirmed the presence of S. citri, and identified a novel, putative arp gene in one carrot sample. S. citri is a phytopathogenic mollicute transmitted by leafhopper species. Beet leafhoppers (Circulifer tenellus Baker) collected in the same state of Zacatecas, Mexico, were subsequently tested for S. citri infection, and 36.5% were positive using PCR targeting the arp1 gene. Sequencing analysis confirmed the presence of S. citri in the leafhoppers. This is the first report of S. citri in carrot and C. tenellus in Mexico. Previously in the Americas, S. citri in carrot was only reported in Washington and California in the United States. The presence of S. citri in carrots and the beet leafhopper in Mexico, suggests that this pathogen could become a threat to vegetable industries in this region of Mexico, including the carrot industry.