Potato (Solanum tuberosum) is an important vegetable crop in Indonesia. A small survey was conducted for virus diseases in November 2011 in Lembang, West Java, as part of assessing the sanitary status of potatoes produced in farmers' fields. Among the six potato fields surveyed, one field had nearly 20% of plants displaying stunted growth with leaves showing mild chlorotic spots and reduced size of lamina. Tubers harvested from symptomatic plants showed no necrosis symptoms. Symptomatic leaves from three representative potato plants were positive for Potato virus Y (PVY) when tested with PVY-specific immunostrips (Agdia Inc., Elkhart, IN). Leaf samples from virus-positive plants were imprinted on FTA Classic Cards (Whatman International Ltd., Maidstone, UK), air dried, and shipped to Washington State University for confirmatory diagnostic tests. Total nucleic acids were eluted from FTA cards (1) and subjected to reverse transcription (RT)-PCR using primers (PVY/Y4A and PVY/Y3S) specific to the coat protein (CP) of PVY (3). Nucleic acid extracts from samples infected with PVY ordinary strain (PVYO), tuber necrosis strain (PVYNTN), tobacco veinal necrosis strains (PVYEU-N and PVYNA-N), and a recombinant strain (PVYN:O) were included as standards to validate RT-PCR assays. The approximately 480-bp DNA fragment, representing a portion of the CP, amplified in RT-PCR was cloned into pCR2.1 (Invitrogen Corp., Carlsbad, CA). DNA isolated from four independent recombinant clones was sequenced from both orientations. Pairwise comparison of these sequences (GenBank Accession Nos. KF261310 to 13) showed 100% identity among themselves and 93 to 100% identity with corresponding sequences of reference strains of PVY available in GenBank (JQ743609 to 21). To our knowledge, this study represents the first confirmed report of PVY in potato in West Java, Indonesia. Studies are in progress to assess the prevalence of PVY in other potato-growing regions of Indonesia and document the presence of different strains of the virus (2). Since the majority of farmers in Indonesia plant seed selected from their previous potato crop, there is an increased risk of primary and secondary spread of PVY through the informal seed supply system, leading to its increased significance to potato production in Indonesia. Therefore, strengthening foundation seed potato and supply chain programs will promote the production of virus-free potatoes in Indonesia.
References: (1) O. J. Alabi et al. Plant Dis. 96:107, 2012. (2) A. Karasev and S. M. Gray. Am. J. Potato Res. 90:7, 2013. (3) R. P. Singh et al. J. Virol. Methods 59:189, 1996.
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