Molecular Identification of an Isolate of Wisteria vein mosaic virus in Khorasan Razavi Province

Wisteria vein mosaic virus (WVMV) is a member of the Potyvirus genus (Potyviridae) with flexuous filamentous particles. The disease was first reported by Brierley & Lorentz (1957) in the USA from W. floribunda. They cited reports of similar cases dating back to the 1940s and suspected that a virus was responsible for the disease. Afterward the virus has been reported in Wisteria spp. in Australia, New Zealand, China, Germany, Czech Republic, Italy and in the Netherland. In comparison to the majority of potyviruses, WVMV has a very narrow host range, naturally infecting only Wisteria spp. (W. sinensis, W. floribunda, and W. venusta). This virus can be introduced into the landscapes on new plants that were infected during their production. Other wisteria can become infected by mechanical inoculation if infected sap is moved on cutting tools or by aphids during feeding from sap of these plants. In terms of symptoms induction, the virus can cause systemic, local chlorotic (sometimes necrotic) lesions or mottling and mosaic on the leaves of wisteria spp. plants and other experimental hosts of Chenopodium spp., Nicotiana megalosiphon and several legumes. The virus is serologically related to Bean common mosaic virus (BCMV), Bean yellow mosaic virus (BYMV), Clover yellow vein virus (ClYVV) and Watermelon mosaic virus (WMV). WVMV is transmitted by aphids, grafting or mechanical means with no significant impact on ornamental host plant except inducing an unfavorable leaf appearance in the landscape. In August 2017, a plant of Wisteria sinensis in the campus of Ferdowsi University of Mashhad in Iran was observed to have chlorotic, mottling and mosaics on some leaves, which resembled the symptoms caused by wisteria mosaic disease. RNA was extracted from the symptomatic plant with an RNeasy Plant Mini Kit (Qiagen, Germany) and tested by RT-PCR using potyvirus degenerate primers CIF/R. Amplicons of the expected size, 680 bp were obtained. The PCR product was cloned and then sequenced. The partial sequence of Nib gene was also amplified (350 bp) by degenerate primer for potyvirus Nib gene and the obtained fragment were cloned and then sequenced. A BLASTn search in the GenBank showed 90.64% nucleotide sequence identity with WVMV Chinese isolate (AY656816) followed by Watermelon mosaic virus (80.67%) and Soybean mosaic virus (80.46%). The least identity was with an isolate of Lettuce mosaic virus (56.34%). It seems that the Chinese and Iranian isolates of this virus are closer to each other but due to lack of nucleotide sequence from other part of the world in CI and Nib genes it is hard to conclude that Iranian isolate is just close to Chinese isolate and it should be considered that may other isolates exist which are closer to Iranian WVMV isolate than Chinese isolate. From this research, it can be concluded that this virus is present in wisteria spp. plant in Khorasan Razavi province of Iran. In terms of sequence similarity based on partial nt sequence of CI gene (680 nt), it is most similar to a Chinese isolate of WVMV (90.64 %) followed by WMV (80.67 %) and SMV (80.46 %) in nt level and within BCMV subgroup of potyviruses. It seems likely that the disease is spread primarily through vegetative propagation rather than by aphid or mechanical transmission. Although the disease does not markedly reduce the vigour of infected plants, the foliage of such plants is chlorotic and mottled, rendering them unsaleable or can cause the ornamental plants as unfavorable host.