|Alabi, O. -|
|Saidov, N. -|
|Naidu, R. -|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 23, 2012
Publication Date: June 25, 2012
Citation: Alabi, O., Crosslin, J., Saidov, N., Naidu, R. 2012. First report of Potato virus Y in potato in Tajikistan. Plant Disease. 96:1074. Interpretive Summary: Potato is an important food crop for the people of the Central-Asian country of Tajikistan. However, little work has been conducted on the occurrence of viruses in the potato crop in this country. Recent work conducted by researchers at the International Center for Agricultural Research in the Dry Areas (ICARDA), Washington State University, and supported by researchers at USDA-ARS, has confirmed the presence of two strains of potato virus Y (PVY) in this country. This finding is particulary important in that one of the strains identified, PVY-NTN, produces pronounced symptoms in potato tubers and renders them unmarketable. These findings inform the international community of the importance of potato viruses in this region and the need to initiate programs for reducing the incidence of PVY in this important source of food in the region.
Technical Abstract: Potato (Solanum tuberosum L.) is widely grown as a staple food and cash crop in Tajikistan and is an important food security crop in the country. In June 2011, we conducted a survey of potatoes in farmers’ fields in Buston and Dushanbe regions of Tajikistan. Potato plants with stunted growth and leaves showing chlorotic spots, curling and necrotic spots and rings were observed with the disease incidence monitored in ten fields each in Buston and Dushanbe areas varying between 10 to 60 percent. Representative samples from symptomatic plants tested positive for Potato virus Y (PVY) using virus-specific immunostrips (Agdia Inc., Elkhart, IN). Leaf samples from symptomatic plants were collected from Buston and Dushanbe areas, imprinted on FTA® Classic Cards (Whatman International Ltd., Maidstone, UK), air dried and brought to the lab for confirmatory diagnostic tests. Viral nucleic acids were eluted from FTA cards (1) and subjected to reverse transcription (RT)-PCR using primers (PVY/Y4A & PVY/Y3S) specific to the coat protein (CP) of PVY (2). Samples infected with PVY ordinary strain (PVYO), tuber necrosis strain (PVYNTN), tobacco veinal necrosis strains (PVYEU-N & PVYNA-N) and a recombinant strain (PVYN:O) were included as references to validate RT-PCR results. A single DNA product of approximately 480 base pairs (bp) was amplified from potato samples tested positive by PVY-specific immunostrips. The amplified fragments from two samples (DP1 & DP4) from Dushanbe and six (BP1, BP2, BP4, BP6, BP7 & BP8) from Buston areas were cloned separately into pCR2.1 (Invitrogen Corp., Carlsbad, CA) and two independent clones per amplicon sequenced from both orientations. Pairwise comparison of these sequences showed 90 to 100% identity among the cloned amplicons (GenBank Accession Nos. JQ743609-16) and 90 to 100% with corresponding nucleotide sequence of reference PVY strains (GenBank Accession Nos. JQ743617-21). A global phylogenetic analysis of sequences revealed the presence of PVYO in three samples (DP1, DP4 and BP1) and presence of PVYNTN in five samples (BP2, BP4, BP6, BP7 and BP8). These results suggest geographic segregation of PVYO and PVYNTN strains with PVYO present in samples from Dushanbe area and both PVYO and PVYNTN present in samples from Buston area. Mixed infection of the two PVY strains were not observed in Buston area. To our knowledge, this study represents the first confirmed report of two distinct strains of PVY in potato in Tajikistan. The occurrence of PVYNTN, a quarantine pathogen in many countries, warrants additional investigations to improve sanitary status of potato fields and to facilitate the availability of virus-free seed in clean plant programs for significant yield increases in Tajikistan.