Watermelon mosaic virus.

Abstract

Potyviruses have been badly affecting crop yields in most parts of the world, with Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV) and Papaya ringspot virus (PRSV) being of particular economic importance. Watermelon mosaic virus (WMV) causes severe economic losses in cucurbitaceous, leguminous, malvaceous and chenopodiaceous plants in temperate and Mediterranean regions. It produces chlorosis, mottling, blisters on leaves and fruits, leaf distortion and stunting in watermelon, muskmelon, squash, pumpkin and cucumber. WMV has been shown to infect experimentally, more than 170 plant species belonging to 27 plant families. The biological variability of WMV has been well-documented. Serologically, it is close to Soybean mosaic virus (SMV) and Papaya ringspot virus (PRSV), but distantly related to Potato virus Y (PVY) and Bean yellow mosaic virus (BYMV). The genome of the reported WMV isolates is more than 10kb, flanked by untranslated regions at both the ends. The large open reading frame (ORF) encodes a putative polyprotein of 3217 aa, with a calculated Mr. of 366,904. Sequence analyses of WMV isolates revealed close relationship with the reported isolates of SMV (84.7% to 85.8% aa identity). However, the N-terminal P1 protein encoding region was substantially different, presenting less than 35% identity. SimPlot analysis revealed that WMV arose through an ancestral event of interspecific recombination between SMV and Bean common mosaic virus (BCMV)/ Peanut stripe virus (PSV)-related potyviruses. Very little genetic material resistant to WMV-2 is available. Cultural practices, crop rotation, cross-protection and genetic resistance have effectively been used against WMV. Coat protein transgenic resistance to WMV has also been reported in squash and cantaloupe.