Effect of biocontrol agent, plant extracts and safe chemicals in suppression of Mungbean Yellow Mosaic Virus (MYMV) in black gram (Vigna mungo)

Abstract

Pseudomonas fluorescens (Pf1), plant extract and bioactive compound treatments on induction of peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL) and accumulation of phenolics in black gram to suppress the natural incidence of Mung bean yellow mosaic bigeminivirus (MYMV) was studied. Leaf extracts of Mirabilis jalapa, Datura metel and neem (Azadirachta indica) oil provided reduced incidence of MYMV with increased yield in black gram under field conditions. The bio-compatible products actigard® (acibenzolar-S-methyl), disodium hydrogen phosphate and alum (aluminium potassium sulphate) also suppressed MYMV on black gram and increased yield compared with nontreated plants under field conditions. The mean disease incidence of the two field trial shows that the foliar spray of P. fluorescens and M. jalapa recorded the lowest disease incidence of 39.14 and 41.48% with yields of 718 and 716.5 kg per hectare, respectively. Induction of systemic resistance as evident from the increased accumulation of pathogenesis related (PR) proteins and other defense related compounds was observed in black gram plants following application of Pf1, plant extracts and bioactive compounds after incidence of MYMV during 30 and 45 days after planting. Black gram with these treatments exhibited a significant increase in activities of enzymes PAL, PO, PPO along with rapid and distinct accumulation of toxic phenolic compounds than the control plants. These results suggest that the enhanced activities of defense enzymes and elevated content of phenolics may contribute to the protection of black gram against MYMV. Further, the inverse correlation of reduced MYMV disease incidence with significantly high chlorophyll content and total sugar contents in Pf1, plant extract and bioactive compounds treated plants also suggest the potential of these treatments to use for managing MYMV in the field.