Oral Technical Session: Resistance to Viruses and Virus Characterization

90-O

Molecular characterization and detection of Mexican papita viroid.
R. LI (1), K. S. Ling (1)
(1) USDA-ARS, U.S. Vegetable Laboratory, Charleston, SC, U.S.A.

Mexican papita viroid (MPVd), in genus Pospiviroid and family Pospiviroidae, was first isolated from wild papita (Solanum cardiophyllum Lindl) plants in 1996. Since 2009, several disease outbreaks on greenhouse tomatoes in Canada and Mexico were shown to be caused by MPVd infection. However, the Koch’s Postulates for MPVd have not been established. In the present study, we engineered infectious cDNA clones using two select MPVd isolates (MX and Mex8). Infectivity of the engineered cDNA constructs was examined by mechanical inoculation of ‘Moneymaker’ tomato plants with their respective in vitro RNA transcripts. After four weeks post inoculation, disease symptoms of stunting and leaf chlorosis on the inoculated plants were similar to those in field observation. The presence of MPVd on the inoculated plants was confirmed with real-time reverse transcription polymerase chain reaction (RT-PCR). Additional cloning and sequencing of MPVd-MX and MPVd-Mex8 progeny revealed that MPVd existed in host plants as a mixture of various sequence variants. However, the predominant progeny sequences were identical to their respective parental cDNA clones, which accounted for 81.82% for MPVd-MX and 78.79% for MPVd-Mex8, respectively. Two species-specific and sensitive molecular detection methods including real-time RT-PCR and reverse transcription loop-mediated isothermal amplification (RT-LAMP) were developed and successfully applied for plant and seed health test.