Bio-consortia of Bacillus spp. induces defense gene expression and suppresses Orthotospovirus arachinecrosis in tomato.

Abstract

Background: Tomato (Solanum lycopersicum L) is affected by various diseases among which Orthotospovirus arachinecrosis cause huge economical loss to the farmers. Management of viral diseases using systemic insecticides will target the beneficial microflora and fauna besides polluting the environment and cause health hazards. In this context, inducing systemic resistance (ISR) through Bacillus spp. is a promising alternative method which is natural, eco-friendly and safe, offering resistance against the disease.

Methods and results: In the present study, eight Bacillus spp. has been tested for their anti-viral efficacy against O. arachinecrosis in tomato. Pre-inoculation spray of the consortium of Bacillus subtilis BST8, Bacillus subtilis EBPBS-4 and Bacillus subtilis Bbv57 as seed treatment (10 ml/kg), soil drenching (1%) and foliar application (0.5%) exhibited less disease severity index of 12.92 compared to inoculated control (85.98) in tomato in pot culture. Field experiments revealed that, sequential application of Bacillus spp. consortia (Bbv57 + BST8 + EBPBS4) formulation as seed treatment, (10 ml/kg), soil application (2 lit/acre) along with foliar spray (1 lit/acre) at 30 DAT, 45 DAT and 60 DAT recorded the lowest disease incidence over control. Defense gene expression studies through real-time PCR analysis revealed that there is differential expression of defense genes viz., PR1, PR2, PR3, NPR1, MAPKK and PAL during the tripartite interaction of Bacillus spp. with O. arachinecrosis in tomato.

Conclusion: It is concluded that, consortia of Bacillus spp. induce systemic resistance in the plant besides promoting plant growth which can be utilized for the management of O. arachinecrosis infecting tomato.