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First Report of Zucchini yellow mosaic virus Associated with Leaf Crinkle and Yellow Mosaic Diseases of Cucurbit Plants in Mali

The aphid-transmitted Zucchini yellow mosaic virus (ZYMV; genus Potyvirus, family Potyviridae) has been reported to cause severe epidemics and yield losses in cucurbit crops worldwide (1). In Africa, ZYMV has been detected in Algeria, Egypt, Madagascar, Mauritius, Mayotte, Morocco, Nigeria, Reunion, South Africa, Sudan, Swaziland, and Tunisia (1). In April 2009, leaf yellowing, mosaic, crinkling, and curling were common on cucurbit plants in fields in Mali. Symptomatic leaf samples were collected from five cucumber (Cucumis sativus) plants in Kati, two watermelon (Citrullus lanatus) plants in Samanko, and one weedy melon (Cucumis sp.) plant in Baguineda. All samples tested positive for ZYMV and were negative for Cucumber mosaic virus (CMV), Cucumber green mottle mosaic virus (CGMMV), Papaya ringspot virus type W (PRSV-W), Watermelon mosaic virus (WMV), and Watermelon silver mottle virus (WSMoV) by double-antibody sandwich (DAS)-ELISA. They also tested negative for Melon yellow spot virus (MYSV) by indirect ELISA. Antibodies against ZYMV and WMV were obtained from DSMZ, Braunschweig, Germany, and those against CGMMV, MYSV, PRSV-W, and WSMoV were provided by Shyi-Dong Yeh, National Chung Hsing University, Taichung, Taiwan. Six ZYMV ELISA-positive samples (three cucumber, two watermelon, and the weedy melon sample) were also tested by reverse transcription (RT)-PCR using the potyvirus universal primer pair Sprimer1/Oligo(dT) (2). The expected 1.6-kb viral cDNA was amplified from all six samples and each was sequenced. All sequences obtained from cucumber (GenBank Accession Nos. HM005307, HM005308, and HM005309), watermelon (GenBank Accession Nos. HM005311 and HM005312), and weedy melon (GenBank Accession No. HM005310) isolates were 1,684 nucleotides (nt) long excluding the 3′ poly-A tails. They comprised the 3′-terminal of the NIb region (1 to 633 nt), the coat protein region (634 to 1473 nt), and the 3′-untranslated region (1,474 to 1,684 nt). Because the sequences shared high nucleotide identity (98.3 to 99.7%), these isolates were considered to be the same virus species. When the sequences were compared by BLASTn searching in GenBank and analyzed by DNAMAN Sequence Analysis Software (Lynnon Corporation, St-Louis, Pointe-Claire, Quebec, Canada), they were found to have the greatest nucleotide identity (97.4 to 98.0%) with the Connecticut strain of ZYMV (ZYMV-Connecticut; GenBank Accession No. D00692), within a clade of isolates from China, Italy, Japan, and the United States. When assessed separately, their coat protein (97.7 to 98.3% nucleotide and 98.9 to 99.6% amino acid identity) and 3′-untranslated regions (96.7 to 97.2% identity) also had greatest homology with ZYMV-Connecticut. To our knowledge, this is the first report of ZYMV infecting cucurbit plants in Mali. ZYMV should be taken into consideration when breeding cucurbit crops for this region, and managing viral diseases.

References: (1) C. Desbiez et al. Plant Pathol. 46:809, 1997. (2) W. S. Tsai et al. Plant Dis. 94:378, 2010.