Abstract This study evaluated tomato plants’ physiological and biochemical changes influenced by the Trichoderma harzianum and the Azospirillum brasilense . This study aimed to determine whether microbial inoculation with T. harzianum and A. brasilense can mitigate water-deficit stress and improve tomato growth, yield, and crop water productivity under different irrigation regimes. The irrigation regime was applied at four levels: no irrigation, 50%, 75%, and 100% of the water requirement (WR), and biological fertilizer was applied in four treatments: control, Trichoderma, Azospirillum, and Trichoderma + Azospirillum. The experiment was conducted as a factorial design, and the effects of irrigation regime and biological fertilizer treatments were statistically significant for most measured traits. The results demonstrated that the highest fresh and dry root weights and leaf area, were observed under the 100% WR combined with the application of biological fertilizers, particularly Trichoderma . Additionally, chlorophyll content was higher under a 100% WR with biological fertilizers. In contrast, The highest contents of carotenoids (22%), anthocyanins (18%), glucose (79%), sucrose (96%), and total sugars (121%) in leaves were observed under no-irrigation conditions. Conversely, the assessment of fruit characteristics revealed that the highest fresh and dry fruit weights, fresh fruit yield and Wp were achieved under the 100% WR combined with applying biological fertilizers, particularly Trichoderma . Azospirillum treatment and combining Trichoderma with Azospirillum achieved the lowest levels of fruit firmness, total soluble solids, and anthocyanin in fruits under a 100% WR. Moreover, the Trichoderma treatment was able to achieve similar performance under 75% WR conditions as the control treatment under 100% WR. Overall, the results indicate that Trichoderma inoculation plays a key role in improving tomato physiological performance and water productivity under different irrigation regimes, with potential implications for sustainable water management.
Dehkordi et al. (2026) studied this question.