Identification of six potato virus Y isolates from Saudi Arabia
Six potato virus Y (PVY) were isolated from 20 potato plants (Solanum tuberosum sp. tuberosum L.) from the Riyadh region of Saudi Arabia showing leaf systemic symptoms (necrotic spots and mild mosaicism). 16 virus-infected plants gave positive indirect enzyme-linked immunosorbent assay (ELISA) results with PVY commercial antiserum. Electron microscopy revealed the presence of rod-shaped particles (300 × 17 nm). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated the 34 kDa viral coat protein and agarose gel of the immunocapture reverse transcription-polymerase chain reaction (IC-RT-PCR) products indicated the 800 bp cp gene. The sequences were aligned together, narrowed to six (one PVY-N and five PVY-O isolates) and then aligned with all published worldwide PVY cp sequences. The highest similarity index among the six isolates was shown between PVY-saudi-O1 and PVY-saudi-O4 (99.9%), while the least involved PVY-saudi-N and PVY-saudi-O3 (99.1%). The phylogenetic analysis of the cp gene nucleotide sequence revealed a cluster of PVY-saudi-N and the Egyptian strain GU980964. The results indicate the need for more sensitive detection of the virus in the imported seeds or tubers from countries, especially in the Middle East like Egypt, to avoid high threat to the Saudi potato trade.
Key words: Reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), coat protein (CP), sequence alignment, similarity index.