Enhancing drought tolerance in Cannabis sativa L. by Trichoderma hamatum through optimized water usage

Drought stress in hemp ( Cannabis sativa L.) is exacerbated by climate change, posing significant abiotic challenges. Trichoderma hamatum , known for mitigating abiotic stresses, was evaluated for its effects on hemp under drought conditions. Hemp plants were subjected to four conditions: control, drought stress, T. hamatum treatment, and T. hamatum with drought stress. Our results show that T. hamatum increases the photosynthesis rate by 303 % and the chlorophyll a and b contents by 29 % and 39 %, respectively, in drought-stressed hemp. T. hamatum treatment on hemp plants enhances the accumulation of secondary metabolites, such as total phenolic content (TPC) and total flavonoid content (TFC), which are crucial for non-enzymatic antioxidant defense mechanisms. Furthermore, the levels of these metabolites showed the greatest increase when treated in combination with drought stress. TPC and TFC were proportional to radical scavenging activities. This indicates that, unlike the antioxidant enzymes that increased only in the drought group, T. hamatum mitigates drought-induced oxidative stress by enhancing the accumulation of secondary metabolites such as phenolic compounds. Transcriptome analysis reveals that T. hamatum restores the overexpression of genes involved in the biosynthesis of proline and branched-chain amino acids, which are increased under drought stress. In the T. hamatum treatment, among the GO categories where more than half exhibited significant differences in expression, 90 % of aquaporin-related genes were upregulated, suggesting that the upregulated aquaporin-related genes enhance water use efficiency under limited water conditions, thereby alleviating drought stress in hemp. • T. hamatum restores the photosynthetic parameters of C. sativa under drought conditions and increases water use efficiency. • T. hamatum mitigates oxidative stress in C. sativa under drought conditions through non-enzymatic antioxidant activities based on secondary metabolites. • T. hamatum restores the overexpression of stress-related mRNAs, such as proline and BCAAs, to normal levels in C. sativa under drought conditions. • The upregulation of aquaporin gene families in C. sativa treated with T. hamatum suggests an association with enhanced drought stress resistance.