Nucleotide Sequencing and Symptomology of Two New Isolates of Watermelon mosaic virus from Razavi and Northern Khorasan Provinces

During 2008-2009, 323 samples showing mosaic, yellowing, vein banding, leaf malformation and blistering were collected from different Cucurbitaceous plant fields and cucumber greenhouses in Razavi and Northern Khorasan provinces. Through doing DAS-ELISA, 95 samples showed infection with WMV. WMV in samples testing positive by ELISA was confirmed by RT-PCR. RT-PCR assay with specific primers corresponding to the virus coat protein gene led to the amplification of the expected DNA fragment with a length of approximately 822 bp. PCR product from two isolates from Zucchini squash (Shirvan) and melon (Torghabe-Shandiz) were sequenced. The sequenced fragments after multiple alignments using ClustalW2 program compared with other GeneBank isolates. Phylogenetic tree was drawn using Neighbor-joining method of MEGA4.1 program. Phylogenetic analysis showed that Iranian isolates of WMV with 92-99 % nucleotide sequence identity and 96-100% amino acid identity with other isolates of WMV. The nucleotide and amino acid sequence homologies of 2 isolates were found to be 99.1% and 99.6%, respectively. The two new isolates were not similar in symptoms on some indicator plants including Cucumis sativus, C. melo var. reticulates, Cucurbita pepo and Citrullus lanatus. These results showed that the two new isolates have high homology with isolates of WMV that previously reported from Iran.