Management of late leaf spot (Phaeoisariopsis personata) and root rot (Macrophomina phaseolina) diseases of groundnut (Arachis hypogaea L.) with plant growth-promoting rhizobacteria, systemic acquired resistance inducers and plant extracts

Abstract

Greenhouse experiments were conducted to study the efficacy of plant growth-promoting rhizobacteria (PGPR) for control of root rot (RR) in groundnut (Arachis hypogaea L.) caused by Macrophomina phaseolina and to test the ability of plant systemic acquired resistance (SAR) inducers and plant extracts to protect groundnut plants from late leaf spot (LLS) caused by Phaeoisariopsis personata. Seed treatment and soil application of a talc-based formulation of B. subtilis strain G1 significantly reduced the incidence of root rot under greenhouse conditions. In experiments with SAR inducers, foliar application of salicylic acid (SA) (7 mM) on 45 days after sowing significantly reduced LLS incidence and increased the pod yield. Foliar application of aqueous extract (10%) from leaves of Adhatoda vasica and zimmu (Allium sativum x A. cepa) on 45 days after sowing significantly decreased the LLS incidence and increased the pod yield compared with the untreated control. Field experiments were conducted to develop an integrated method for the management of LLS and RR of groundnut using the best performing PGPR, SAR inducer and plant extract in combinations. Combined application of B. subtilis strain G1 through seed (10 g/kg) and soil (2.5 kg/ha) followed by foliar application of A. vasica extract (10%) on 30, 45 and 60 days after sowing significantly reduced LLS and RR diseases in groundnut and increased the pod yield under field conditions. The above treatment resulted in significant reductions in the area under the disease progress curve (AUDPC) for LLS compared with that of untreated control.