First Report of Recombinant Potato virus Y Strains Infecting Potato in Jordan

Potato (Solanum tuberosum L.) is an important vegetable crop in Jordan, occupying second position after olives. In 2012, potatoes were planted on about 6,000 ha with a production of about 141,000 t (2). Potato virus Y (PVY) is a serious problem for potato production worldwide. Recombinant strains of the virus were reported to cause tuber necrotic ringspot disease (PTNRD) in many potato-growing regions of the world. In the last few years, a new recombinant PVY that belongs to PVY (3) has been reported in the neighboring Syria. It included three recombination patterns, SYR-I, SYR-II, and SYR-III, and caused severe PTNRD (1). Since PVY is easily transmitted from one region to another by aphid vectors and infected potato seeds, this study was initiated to investigate the possible occurrence of PVY strains in Jordan. In October 2013, 33 leaf samples were collected from symptomatic potato plants cv. Spunta from Wadi Rum, Jordan (GPS coordinates 29°31'37.76″ N, 35°42'48.75″ E), the largest potato-producing area in Jordan. Sampled plants displayed leaf mottling and yellowing, symptoms similar to those caused by PVY. All samples were tested for PVY by DAS-ELISA using the ELISA kit (monoclonal cocktail) developed by BIOREBA (Reinach, Switzerland) to detect all PVY isolates. Twenty-nine samples were found positive for PVY by ELISA. To confirm virus infection, total RNA was extracted from all ELISA-positive samples and used as template in uniplex RT-PCR using strain-specific primers (1). The band pattern of PCR amplicons showed that 12 samples were infected with PVY genotype SYR-III and produced bands of 1,085, 441, and 278 bp. One sample was infected with PVY (A) and produced bands of 1,307, 633, and 441 bp, and one other sample was infected with PVY genotype SYR-II and produced bands of 1,085 and 441 bp. Mixed infection with PVY genotype SYR-III and PVY (B) was also detected in one sample producing bands of 278, 441, 1,085, and 1,307 bp. To confirm infection with the recombinant strains, PCR fragments of 278 bp amplified from three samples and 1,085 bp obtained from another three samples were directly sequenced and sequences were deposited in GenBank under accession numbers KJ159968, KJ159969, and KJ159970 for the 278-bp fragment and KJ159974, KJ159975, and KJ159976 for the 1,085-bp fragment. Sequence comparison with other PVY strains available in the NCBI database showed that the 278-bp fragment had the highest nucleotide sequence identity (100%) with PVY isolates