Biocontrol Potential of Salt-Tolerant Trichoderma and Hypocrea Isolates for the Management of Tomato Root Rot Under Saline Environment

Abstract

The aim of present study was to decipher the effect of salinity stress on growth and antagonistic potential of Trichoderma and Hypocrea isolates against tomato root rot pathogen (Rhizoctonia solani AG-4) under saline soil conditions. In vitro salinity assays, dual plate confrontation, and volatile metabolite assays were employed to establish the antagonistic potential of Trichoderma and Hypocrea isolates against R. solani AG-4 under varied salt gradients. Potential Trichoderma and Hypocrea isolates were evaluated against tomato root rot disease in greenhouse conditions under salt stress condition. Polymerase chain reaction (PCR) assay was performed to confirm the presence of endochitinase gene in salt-tolerant antagonists. Enzyme and biochemical assays were conducted to define the role of compatible solutes and defense-related enzymes in controlling tomato root rot under saline soil conditions. Trichoderma and Hypocrea isolates were capable to grow and sporulate up to 250 mM NaCl and also showed strong antagonism against R. solani. Enzymatic estimation of hydrolytic enzymes and amplification of endochitinase gene suggested that the test isolates are potent antagonistic agents. Under greenhouse evaluation, Trichoderma and Hypocrea fortified tomato plants showed significant reduction in tomato root rot disease in saline soils over untreated control. Significant increase in total phenol, polyphenol oxidase, peroxidase, β-1,3-glucanase, phenylalanine lyase, chitinase, proline, reducing sugar, and total soluble sugar displayed direct association with salt stress tolerance. Application of salt-tolerant Trichoderma and Hypocrea isolates emerged as a simple, safe, and cheap method for the biological management of tomato root rot under saline condition.