Induction of Systemic Resistance by Biocontrol Agents against Bacterial Blight of Cotton Caused by Xanthomonas campestris pv. malvacearum

Abstract

Bioagents such as Trichoderma harzianum, Pseudomonas fluorescens and Bacillus subtilis were isolated from cotton rhizosphere soil and tested individually for their effectiveness in controlling bacterial blight of cotton caused by Xanthomonas campestris pv. malvacearum (Xcm). Talc based formulations were prepared and used for seed treatment at different concentrations for assessing their ability to stimulate plant growth and to control bacterial blight disease. Among bioagents, P. fluorescens and T. harzianum proved to be effective in controlling disease under field conditions. Other than direct action, these bioagents triggered the defense related enzymes involved in synthesis of phenols. Higher activity of peroxidase, phenylalanine ammonia-lyase, polyphenol oxidase and b-1,3-glucanase was observed in P. fluorescens and T. harzianum treated cotton plants after challenge inoculation with Xcm. Seed treatment with these bioagents enhanced the seed germination and growth parameters against blight disease and they also induced systemic resistance in plant for defense mechanisms.

Trichoderma hamatum can act as an inter-plant communicator of foliar pathogen infections by colonizing the roots of nearby plants: A new inter-plant “wired communication”

“…This specific SA-mediated activation of systemic resistance by Trichoderma-roots colonization has been reported against other hemibiotrophic pathogens, such as X. campestris pv. malvacearum on cotton colonized by T. harzianum (Raghavendra et al, 2013), the fungus Colletotrichum graminicola in Fig. 6.…”