Induced resistance against Fusarium solani root rot disease in cassava plant ( Manihot esculenta Crantz) promoted by salicylic acid and Bacillus subtilis

Abstract

Root rot disease of cassava is one of the major diseases in Thailand, widespread incidence of soil-borne pathogens has been found to affect more than 80%. The research aims to investigate the effect of elicitors as salicylic acid and Bacillus subtilis strain JN2-007 for inducing resistance against root rot disease by Fusarium solani in cassava. The experiment was carried out in a susceptible cassava cultivar to test the efficacy of elicitors in the biochemical response of plant defense mechanisms pertaining to hydrogen peroxide (H₂O₂) and enzyme activities. The results indicated that pathogenicity test of F. solani isolate SHRD1 caused the brown lesions around the inoculation point on cassava roots. Subsequently, salicylic acid and JN2-007 reduced mycelial growth of F. solani (11.83%–57.73% at day 7), as well as disease severity in the cassava plants at 14 days after the inoculation compared to that of the negative control (28.12%–39.58% compared to 68.75%). Furthermore, salicylic acid at a concentration of 500 µl. L⁻¹ could induce H₂O₂, level of peroxidase, polyphenol oxidase, and catalase activities that were highest at 24 h after pathogen inoculation. The results suggested that elicitors played an important role as a plant defense inducer, leading to reduced Fusarium root rot disease.