Deciphering the antimicrobial activity of multifaceted rhizospheric biocontrol agents of solanaceous crops viz., Trichoderma harzianum MC2, and Trichoderma harzianum NBG

Abstract

The <i>Solanaceae</i> family is generally known to be the third most economically important plant taxon, but also harbors a host of plant pathogens. Diseases like wilt and fruit rot of solanaceous crops cause huge yield losses in the field as well as in storage. In the present study, eight isolates of <i>Trichoderma</i> spp. were obtained from rhizospheric micro-flora of three solanaceous crops: tomato, brinjal, and chili plants, and were subsequently screened for pre-eminent biocontrol activity against three fungal (<i>Fusarium oxysporum</i> f. sp. <i>lycopersicum</i>, <i>Colletotrichum gloeosporioides</i>, and <i>Rhizoctonia solani</i>) and one bacterial (<i>Ralstonia solanacearum</i>) pathogen. Morphological, ITS, and <i>tef1α</i> marker-based molecular identification revealed eight isolates were different strains of <i>Trichoderma</i>. Seven isolates were distinguished as <i>T. harzianum</i> while one was identified as <i>T. asperellum</i>. <i>In vitro</i> antagonistic and biochemical assays indicated significant biocontrol activity governed by all eight isolates. Two fungal isolates, <i>T. harzianum</i> MC2 and <i>T. harzianum</i> NBG were further evaluated to decipher their best biological control activity. Preliminary insights into the secondary metabolic profile of both isolates were retrieved by liquid chromatography-mass spectrometry (LC-MS). Further, a field experiment was conducted with the isolates <i>T. harzianum</i> MC2 and <i>T. harzianum</i> NBG which successfully resulted in suppression of bacterial wilt disease in tomato. Which possibly confer biocontrol properties to the identified isolates. The efficacy of these two strains in suppressing bacterial wilt and promoting plant growth in the tomato crop was also tested in the field. The disease incidence was significantly reduced by 47.50% and yield incremented by 54.49% in plants treated in combination with both the bioagents. The results of scanning electron microscopy were also in consensus with the <i>in planta</i> results. The results altogether prove that <i>T. harzianum</i> MC2 and <i>T. harzianum</i> NBG are promising microbes for their prospective use in agricultural biopesticide formulations.