Trichoderma gamsii strain TC959 with comprehensive functions to effectively reduce seedling damping-off and promote growth of pepper by direct and indirect action mechanisms

A few Trichoderma species have been utilized as biocontrol agents in agriculture due to their ability to inhibit growth of phytopathogens. However, the antagonistic mechanism of some strains is mainly performed by direct action. The objective of our study is to explore an effective strain that has comprehensive abilities, and preliminarily clarify its practical viability and action mechanism. Trichoderma gamsii strain TC959 possessing abilities of strong antagonism and plant growth promotion was singled out. It released secondary metabolites, siderophores and chitinase/xylanase to directly inhibit the growth of plant pathogens, or released indole-3-acetic acid/gibberellin to promote plant growth. The strain also activated induced systemic resistance by increasing chlorophyll a/b ratio and jasmonic acid content of pepper seedlings through root colonization, which resulted in the improvements of defense-related gene expression levels, antioxidant enzyme activity, and indole-3-acetic acid/gibberellin production. Thereby disease resistance and plant growth were enhanced and promoted, respectively. Furthermore, TC959 had a resistance advantage to oxidation and chemical fungicides, which helped viability of the strain to be maintained, and healthy pepper seedlings were effectively ensured. In conclusion, strain TC959 has biocontrol potential and comprehensive functions against pepper damping-off disease, which is valuable for further practical applications.