Biodiversity, phylogeny, thermotolerance and biocontrol traits of novel Trichoderma isolates from Brazil's Caatinga...

Trichoderma species are recognized as versatile fungi with significant roles in biocontrol of plant diseases, promoting plant growth and safeguarding against various environmental threats. Despite their benefits, the biodiversity of indigenous Trichoderma isolates in the semi-arid region of Brazil's Caatinga biome remains largely unexplored. This untapped diversity holds promise for identifying potential biocontrol agents against soilborne plant pathogens. Here, we conducted molecular identification and morphological characterization of 14 indigenous Trichoderma isolates from both undisturbed (native) and melon agricultural areas of the Caatinga biome. Subsequently, we evaluated the direct antagonism (competition or mycoparasitism) and volatile compounds (VCs) antibiosis of these Trichoderma species against five representative soilborne plant pathogens: Fusarium sulawesiense, Fusarium solani, Macrophomina phaseolina, Rhizoctonia solani, and Pythium myriotylum. A distinct Trichoderma species composition was observed in undisturbed and cultivated areas, influenced by soil chemical properties. Thermotolerance was found to be more associated with ecological niche than specific species or isolates, with isolates from melon-grown areas exhibiting higher heat tolerance. Isolates from both undisturbed and cultivated area demonstrated antagonism through competition-mycoparasitism and VCs-mediated antibiosis, though the impact on pathogens varied. Trichoderma asperelloides and Trichoderma aperellum from melon-grown areas stood out as the best conidial producers by solid-state fermentation. Our findings highlight key biocontrol traits in Trichoderma species alongside their thermotolerance and conidial production, underscoring their potential for development as biocontrol agents in the Caatinga biome. We also discuss the implications of these findings for employing Trichoderma in biological control strategies against soilborne diseases in challenging environmental conditions.