RESUMEN
In Jordan, as well as many countries in the region, tomato production is threatened by begomoviruses belonging to the tomato yellow leaf curl virus complex (1). In 2013, an experiment was conducted at Homret Al-Sahen, Jordan (GPS coordinates 32°05'06â³ N, 35°38'52â³ E), to evaluate different tomato breeding lines for resistance against viruses causing tomato yellow leaf curl disease (TYLCD). Disease symptoms, typical of those caused by TYLCV complex, were observed in many susceptible lines. However, some lines exhibited unusual symptoms including severe leaf curling and stunting. To identify the causal agent of these symptoms, total nucleic acids were extracted from 21 symptomatic plants and used as templates in PCR analysis using nine primers, previously described to detect Tomato yellow leaf curl virus, Tomato yellow leaf curl Sardinia virus, and two recombinants between TYLCV and TYLCSV (3). In addition, the universal primer pair ß01/ß02 (2) was used to investigate the association of satDNA ß with the disease. The PCR products characteristic of TYLCV (664 bp) could be amplified from five plants indicating single infection, while double infection with TYLCV and satDNA ß (1,320 bp) was detected in seven plants. Mixed infection with TYLCV, TYLCSV (628 bp), and satDNA ß was detected in another seven symptomatic plants and only one plant was infected with TYLCV and TYLCSV. A single plant had mixed infection with TYLCV, TYLCSV, and RecA (a recombinant between TYLCV/TYLCSV) (538 bp) (3). Amplicons obtained from two plants using ß01/ß02 primers were directly sequenced as 1,320-bp PCR products. Both sequences were found identical and, therefore, this sequence was deposited in the GenBank under the accession number KJ396939. Phylogenetic analysis revealed that this satDNA ß sequence had the highest nucleotide (95%) identity with Okra leaf curl virus (OkLCV) satDNA 3 (AF397217) and OkLCV satDNA 10 (AF397215). The contribution of the satDNA ß in the modulation of the TYLCD symptoms will be further investigated. Few years ago, another satDNA (Tomß01-Om) was reported in Oman to be associated with TYLCD (4). However, to the best of our knowledge, this is the first report on the detection of satDNA ß in tomato plants infected with viruses causing TYLCD in Jordan. The increasing diversity of begomoviruses causing TYLCD in the region is of great concern due to the possible emergence of more virulent viruses and subsequent increased losses to tomato production. References: (1) G. Anfoka et al. J. Plant Pathol. 90:311, 2008. (2) R. W. Briddon and J. Stanley. Virology 344:198, 2006. (3) S. Davino et al. Virus Res. 143:15, 2009. (4) A. J. Khan et al. Virus Gene 36:169, 2008.
RESUMEN
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 PVYNTN-NW that belongs to PVYZ (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°31'37.76â³ N, 35°42'48.75â³ 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 PVYNTN-NW genotype SYR-III and produced bands of 1,085, 441, and 278 bp. One sample was infected with PVYNTN (A) and produced bands of 1,307, 633, and 441 bp, and one other sample was infected with PVYNTN-NW genotype SYR-II and produced bands of 1,085 and 441 bp. Mixed infection with PVYNTN-NW genotype SYR-III and PVYNTN (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 SYR-III-A26 (AB461467) and SYR-III-2-4 (AB461457) from Syria. BLAST searches also showed that the 1,085-bp fragment shared 99% nucleotide identities with PVY isolates SYR-II-L3 (AB461482) and SYR-II-Be4 (AB461474) from Aleppo, Syria. To our knowledge, this is the first report of PVY recombinants in Jordan, and the first report of PVYNTN-NW recombinants infecting potato crop outside Syria. Since Europe is the main supplier of potato seeds for farmers in Jordan and Syria, the introduction of PVYNTN-NW to the region could have happened through infected potato seeds. Results of this study create new challenges for potato growers in Jordan as well as other countries in the region. References: (1) M. Chikh Ali et al. J. Virol. Methods 165:15, 2010. (2) FAO. http://faostat.fao.org/ (3) A. V. Karasev and S. M. Gray. Ann. Rev. Phytopathol. 51:571, 2013.