Egyptian leek (Allium ampeloprasum), garlic (A. sativum), and onion (A. cepa) are key vegetables produced by small- and large-scale farmers in Egypt for national and international markets. Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is an economically important viral pathogen of bulb and seed onion crops in many onion-growing areas of the world (1,3). During February and March of 2011, symptoms of spindle-shaped, straw-colored, irregular lesions with occasional green islands were observed on onion, garlic, and Egyptian leek cultivated on large and small farms in Dakahlia, Gharbia, Kalubia, Menofia, Qena, and Assiut governorates in Egypt. The presence of IYSV was confirmed by specific double antibody sandwich (DAS)-ELISA Flash Kits (Agdia Inc., Elkhart, IN) (2). A survey was carried out by collecting 100 plant samples (10 asymptomatic and 90 symptomatic) of each plant species from fields in the governorates of Dakahlia, Gharbia, Kalubia, Menofia, Qena, and Assiute and testing the plants using DAS-ELISA. For onion and garlic, 45% of the symptomatic samples and 0% of the asymptomatic plants tested positive. For leek, 34% of the symptomatic samples tested positive and 0% of the asymptomatic samples. ELISA-positive samples were tested using a reverse transcription (RT)-PCR assay with primers specific to the S RNA of IYSV (forward primer 5′-TAAAACAAACATTCAAACAA-3′ and reverse primer 5′-CTCTTAAACACATTTAACAAGCAC-3′) (2). Amplicons of approximately 1,100 bp were obtained from all symptomatic samples that were ELISA positive, but none of the asymptomatic plants nor the sterile water control sample produced PCR amplicons. The amplicons were cloned (at least three clones per plant species) using the TOPO TA Cloning Kit (Invitrogen, Grand Island, NY), and sequenced. The Egyptian onion IYSV isolate (GenBank No. JN541273) had the greatest nucleotide sequence identity (86%) with the corresponding S RNA region of IYSV isolates from India (GenBank Nos. EU310290, EU310284, and EU310276). The Egyptian garlic IYSV isolate (GenBank No. JN541275) showed the strongest identity (93%) with that of a Sri Lankan IYSV isolate (GenBank No. GU901211). The Egyptian leek IYSV isolate (GenBank No. JN541274) exhibited 91% sequence identity with that of the same Sri Lankan isolate (No. GU901211). To our knowledge, this is the first report of IYSV infecting garlic and Egyptian leek in Egypt. IYSV infection of onion was reported previously from the agricultural farm of the Faculty of Agriculture, Cairo University, Giza (4), but to our knowledge, this is the first report of natural infection by the virus in commercial onion production in Egypt. Further surveys and monitoring of IYSV incidence and distribution in the entire Egyptian governorate are under investigation.
References: (1) D. H. Gent et al. Plant Dis. 88:446, 2004. (2) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (3) H. R. Pappu et al. Virus Res. 141:219, 2009. (4) A. Manal et al. Egypt. J. Virol. 3:49, 2006.