Effect of Bacillus subtilis on potato virus Y (PVY) disease resistance and growth promotion in potato plants

Potato virus Y (PVY) has become the most important viral pathogen of potato. The Bacillus subtilis EMCCN 1211 (B. subtilis) isolate was investigated in the current study as a biocontrol agent for the management of the PVY and Induced Systemic Resistance (ISR) in potato plants under greenhouse conditions. Foliar and soil applications of a B. subtilis suspension at a concentration of 10(8) CFU/mL was applied at 48 h and 10 days respectively, before and after inoculation with PVY. Treatment of B. subtilis before virus inoculation resulted in a significant reduction in symptoms and entirely negative enzyme-linked immunosorbent assay (ELISA) results compared to untreated infected potato plants. In contrast, the RT-PCR showed PVY amplification (825 bp) in all bacterially treated plants. The soil application using B. subtilis before the PVY inoculation efficiently induced plant resistance and reduced the PVY accumulation level (32.79%) at 10 days post-inoculation (dpi) and continue with percentage increase of virus inhibition up to 72.26% at 35 dpi. The B. subtilis stimulated the plant growth that the potato plants fresh and dry weights increased by 61.40 and 56.6% at p <= 0.05 respectively. The transcriptional changes of pathogenesis -related gene (PR-1) was tested at 10 dpi. The results showed that the lower PVY accumulation was associated with the lower suppression of PR-1 defense related gene expression at 10 dpi and showed 0.9659 fold change value comparing with the mock-inoculated control. This data revealed that the soil application of B. subtilis efficiently suppressed, reduced the PVY accumulation level and symptoms severity; therefore it can be used as an antiviral biocontrol agent.