Molecular Characterization of Two Alfalfa Mosaic Virus Isolates Infecting Potato Crop in Central Region of Saudi Arabia

During the autumn growing season 2012 thirty-two leaf samples of potato (Solanum tuberosum L. cv. Herms) plants showing mottling symptoms suspected to be due to viral infection were collected from Hail and Wadi aldawasser regions in Saudi Arabia. These leaf samples were tested serologically using DAS ELISA against Alfalfa Mosaic Virus (AMV). Twenty-three out of the thirty-two samples were positive for AMV. To determine host range plant sap was extracted from two diseased potato samples representing the two regions and different healthy plants were mechanically inoculated. The disease symptoms induced by the two selected isolates were divided into three groups: systemic and calico symptoms local chlorotic lesions and non-symptomatic ones. Total RNA was extracted from different plants showing positive reaction to AMV. RT-PCR was performed using AMV coat protein specific primers. Approximately 700-bp RT-PCR products were amplified and these PCR products were sequenced in both directions. Nucleotide sequencing analysis showed that these two Saudi Arabian AMV isolates [AMV-PSA-Ha (for the Hail isolate) and AMV-PSA-Wd (for the Wadi Al Dawasser isolate] had a 96.5% identity. Sequence comparison showed that these two isolates of AMV shared 93.2% to 99.7% sequence similarity with the twenty- eight reported isolates of AMV obtained from GenBank. The cDNA probe was prepared and hybridized with RNA extraction from symptomatic potato plants. No hybridization was shown with RNA extracts from asymptomatic plants. This is the first report on the genetic variability of AMV isolates infecting potato crop in Saudi Arabia. Copyright 2014 Friends Science Publishers