Molecular surveillance and identification of emerging viruses affecting yard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verde.] in the Ilocos Region, Philippines
2024
Angeles, Y.B.
The Milk Vetch dwarf virus (MDV). which belongs to Genus Nanovirus, Family Nanoviridae, was first identified infecting milk vetch (Astragalus sinicus) in Japan. Later, it expanded its hosts to cowpea, broadbeans, yardlong beans in China and Bangladesh, papaya, lilliums, Catharanthus roseus in South Korea and Bangladesh, and tobacco, pepper, and tomato in China. In 2022, the presence of the MDV was first reported in the Philippines. affecting yardlong beans in Batangas and Cavite. In this study. molecular surveillance involving virus detection by polymerase chain reaction (PCR) and nucleotide sequencing has detected and identified the associated MDV with the diseased yardlong beans in the Ilocos region. Plants with symptoms of severe stunting, leaf rolling, yellowing, puckering, crinkling, small leaves, and clustering of axillary buds were positive for MDV. PCR using primer pairs that amplify the DNA-S, which codes for the coat protein, has detected MDV in 49 of 146 symptomatic samples, while the samples were negative for begomovirus. BLASTn analysis showed that the isolates had the highest nucleotide sequence identities of 80.15-95.60% with the DNA-S of virus isolates from cowpeas in China and 89.92-93.51% with the MDV coat protein gene in broadbean also from China. Phylogenetic analysis further revealed that the isolates shared a 72% identity with the MDV isolate AHMDV 190520 coat protein gene and MDV isolate HF coat protein (CP) gene. MDV has emerged infecting yardlong beans, and has become a threat to the production of non-legumes in the country. Monitoring the occurrence of the virus is necessary to prevent further spread of the disease.
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