Watermelon is a crop of significant importance to Brazil due to its economic and social aspects, mainly in the northern and northeastern regions. Watermelon plants can be naturally infected by several viruses in single or mixed infections, where the diagnosis is difficult and requires specific techniques.
Scientists at Federal University of Tocantins have detected and verified the presence of Cucumber mosaic virus (CMV), Papaya ringspot virus type W (PRSV-W), Watermelon mosaic virus (WMV), Zucchini lethal chlorosis virus (ZLCV), Zucchini yellow mosaic virus (ZYMV), and the main cucurbit viruses in Brazil by using multiplex reverse transcriptase polymerase chain reaction (RTPCR) assay.
Symptoms of the viral infection of watermelon plants obtained from the main watermelon producing regions in the state of Tocantins.
Leaf samples from the infected watermelon plants in the reproductive stage, at the main watermelon producing regions of the municipalities of Gurupi, Porto Nacional, Lagoa da Confusão, and Formoso do Araguaia of Tocantins state were collected and analysed.
Oligonucleotides were designed towards the conserved regions of the virus genomes. The duplex-PCR allowed to detect all the virus combinations, except ZLCV with ZYMV. The amplified product sizes were 644 bp (CMV), 535 bp (WMV-2), 398 bp (PRSV-W), 244 bp (ZLCV), and 214 bp (ZYMV). Mixed infections were detected in 80% of samples in all the municipalities.
"Virus detection by rapid and reliable techniques can be important tools in plant virology for disease control in production fields to phytosanitary barriers. The current panorama of watermelon production in Brazil and the world indicates that an effective simultaneous detection and differentiation of CMV, PRSV-W, WMV, ZLCV, and ZYMV is required due to the natural occurrence of these viruses in mixed infections," the scientists explained. "To our knowledge, this is the first report on the use of mRT-PCR for simultaneous detection of these five viruses that affect watermelon crop in Tocantins. The mRT-PCR assays developed will provide a simple method for the detection of multiple viruses in watermelon culture in Brazil. Moreover, the specificity of the oligonucleotides allows the development of epidemiological, spatial, and temporal distributions of the virus under study".
Source: Raimundo Wagner de Souza Aguiar, Adelmo Rodrigues Martins, Vitor L. Nascimento, Aristóteles Capone, Lara Teixeira Melo Costa, Fabrício Souza Campos, Rodrigo Ribeiro Fidelis, Gil Rodrigues dos Santos, Renato de Oliveira Resende, Tatsuya Nagata, 'Multiplex RT-PCR identification of five viruses associated with the watermelon crops in the Brazilian Cerrado', 2019, African Journal of Microbiology Research, Vol. 13(3), pp. 60-69.