Bhendi yellow vein mosaic virus and bhendi yellow vein mosaic betasatellite cause enation leaf curl disease and alter host phytochemical contents in okra

Whitefly-transmitted begomoviruses cause severe diseases in numerous economically important dicotyledonous plants. In recent years, okra enation leaf curl disease (OELCuD) emerged as a serious threat to okra (Abelmoschus esculentus L. Moench) cultivation in the Indian subcontinent. The present study reports the association of a monopartite begomovirus (bhendi yellow vein mosaic virus - BYVMV) and betasatellite (bhendi yellow vein mosaic betasatellite - BYVB) with OELCuD in the Mau region of Uttar Pradesh, India. The BYVMV alone inoculated N benthamiana and A esculentus cv. Pusa Sawani plants developed mild symptoms. Co-inoculation of BYVMV and BYVB resulted in a reduced incubation period, an increased symptom severity and an enhanced BYVMV accumulation (by Southern hybridization and qPCR). This is the first study which satisfies Koch's postulates for OELCuD in its natural host. Activities of various antioxidative enzymes were significantly increased in the virus inoculated okra plants. Differential responses in various biochemical components (such as photosynthetic pigments, phenol, proline, sugar) in diseased okra plants were observed. This change in phytochemical responses is of significant importance in understanding its impact on virus pathogenesis and disease development.