The status of Grapevine leafroll-associated viruses in Iran

Infection by plant viruses is one of the most important factors affecting plant productivity and longevity. Slow declines and rapid collapse of plants are mainly related to infection by viruses and phytoplasmas. Grapevine leafroll disease (GLD), caused by a group of serologically distinct viruses known as Grapevine leafroll-associated viruses (GLRaVs, Closteroviridae), is supposed to be the main factor in decreasing the quality and quantity of grapes and longevity of grapevine plants. In order to revise the Iranian national standards for grapevine plant propagating materials in certification schemes, surveys were carried out in the vineyards of the main grapevine producing provinces of Iran namely Western-Azerbaijan, Qazvin, Fars, Khorasan Razavi, Khorasan Shomali and Chaharmahal Bakhtiari. Leaf samples showing symptoms of GLRaVs were collected from 68, 92, 65, 74, 27 and 45 plants, respectively, during the 2014-2016 growing seasons. Samples were first processed in liquid nitrogen and checked for GLRaV-1+3, GLRaV-2 and GLRaV-4-9 by double antibody sandwich enzyme-linked immunosorbent assay using the specific antibodies purchased from the Agdia (USA). Genomic RNA was then extracted from all samples using RNA extraction Kit (GeneAll, South Korea) and the presence of viruses was rechecked by reverse-transcription polymerase chain reactions applying virus specific primer pairs. GLRaV-1+3, GLRaV-2 and GLRaV-4-9 were detected from 2, 5, 1 (Western-Azerbaijan), 4, 0, 0 (Qazvin), 52, 0, 2 (Fars), 17, 0, 1 (Khorasan Razavi), 9, 0, 1 (Khorasan Shomali), and 13, 0, 0 (Chaharmahal Bakhtiari) samples, respectively. Except for the Western-Azebaijan province, GLRaV-1+3 seems to be the most predominant GLRaV in all vineyards. GLRaV-3 has been shown to be the main causal agent of GLD worldwide and then could be a big threat for the Iranian grape industry.