Abstract
More than 100 alkaloids have been found in periwinkle, of which vincristine and vinblastine are the most notable for the treatment of diseases such as leukaemia. In this study, characterization of naturally occurring Cucumber mosaic virus (CMV) infection showed mosaic, leaf deformation and stunting of plants. Viral identification was confirmed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with a specific CMV polyclonal antibody and reverse transcription PCR with a specific primer for the CMV-RdRp-gene, which yielded a 513 base pair DNA fragment. The effect of CMV infection on the antineoplastic alkaloids in periwinkle leaves was determined. We also studied the effect of using plant-growth-promoting rhizobacteria (PGPR) isolates against virus infection to stimulate resistance induction in host plants. Bacillus subtilis 281 and B. pumilus 293 were examined individually (B1 and B2) and in a mixture (B1&B2) for their effectiveness against infection with CMV. The results of greenhouse experiments were confirmed by artificial mechanical inoculation. The PGPR strain treatments and results were reinforced by analysing the protein patterns as well as determining the total phenol, total flavonoid and total alkaloid contents. PGPR treatment evidently lowered the virus concentrations, the percentage of infected plants and the disease severity compared with healthy and infected controls. Seedlings treated with the B1&B2 strain mixture yielded significantly lower levels of virus infection than B1 or B2 individually in all experiments compared to controls. Our findings demonstrate the possibility of using selected Bacillus spp. strains to induce systemic resistance for CMV infection control.