Combined iron (Fe) deficiency and drought stress frequently occur in agricultural soils and can severely impair crop growth, nutrient acquisition, and physiological performance. Beneficial microorganisms have emerged as promising tools for enhancing plant resilience under adverse environmental conditions. This study evaluated the effects of Trichoderma afroharzianum T22 on four maize genotypes exposed to combined Fe deficiency and drought stress. Plant growth, chlorophyll content, relative water content, rhizosphere siderophore production, and expression of the alternative oxidase-associated gene ThAOX1 were assessed after six weeks of growth. Combined stress reduced root length, root biomass, shoot height, shoot biomass, chlorophyll content, and RWC across all genotypes. Inoculation with T. afroharzianum T22 partially mitigated these reductions, although responses varied among genotypes. Genotypes MSIRI3B and CHZM-07-134 exhibited the strongest responses to fungal inoculation, showing greater improvements in growth parameters and physiological traits than R243 and Hi-47. Expression of ThAOX1 increased significantly in MSIRI3B and CHZM-07-134 under stress + TA and TA+ treatments, whereas no significant changes were detected in R243 and Hi-47. Rhizosphere siderophore production was also enhanced by fungal inoculation, particularly in MSIRI3B and CHZM-07-134, with the highest values observed under stress + TA treatment. The results demonstrate that T. afroharzianum T22 influences plant growth, water status, rhizosphere siderophore production, and alternative oxidase-associated gene expression under combined Fe deficiency and drought stress. The magnitude of these responses was genotype dependent, with MSIRI3B and CHZM-07-134 exhibiting greater responsiveness to fungal inoculation than R243 and Hi-47. These findings highlight the potential of T. afroharzianum T22 as a microbial biostimulant for improving maize performance under multiple environmental stress conditions.
