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Poster: Molecular & Cellular Plant-Microbe Interactions: Biotechnology


A single nucleotide polymorphism at the right terminal region of Mexican papita viroid is a virulent determinant factor on tomato
K. LING (1), R. Li (1) (1) USDA-ARS, U.S. Vegetable Laboratory, U.S.A.

Mexican papita viroid (MPVd), a pospiviroid, causes serious disease outbreaks on greenhouse tomato in North America. Two dominant genotypes (MPV-S and MPV-M), sharing 93.8% sequence identity, incited striking different symptom expression (severe and mild) on tomato ‘Rutgers’. To determine genetic factor that is responsible for differential pathogenicity, using synthetic DNA approach, a series of chimeric infectious clones were generated through progressive replacement of each secondary structural domain in MPVd-M with their corresponding domain of MPVd-S. In plant inoculation assays, a chimera containing the Terminal Right domain of MPVd-S incited severe symptom on tomato similar to that induced by MPVd-S. The other three chimeras incited only mild symptoms similar to that of MPVd-M. A single nucleotide polymorphism in the Terminal Right region between MPVd-M (176U:A185) and MPVd-S (174G:C183) was identified as the virulent determinant factor for MPVd. This result supports variable pathogenicity functions in different pospiviroids, which may lead us to design a better strategy in managing this emerging viroid disease.