Unlocking the potential of Trichoderma harzianum isolate Zag-1 to boost drought tolerance in maize plants

Drought stress is main abiotic constraint restrictive maize (Zea mays L.) growth worldwide. An effective agricultural approach to enhance its growth under this stress is the plant growth-promoting microorganism’s application. In this study, Trichoderma harzianum isolate Zag-1 was evaluated for its potential to mitigate drought-induced damage in maize plants. At first, T. harzianum was isolated from pepper plant’s rhizosphere soils, and its growth-promoting characteristics were assessed, including indole-3-acetic acid (IAA), hydrolytic enzymes (chitinase, amylase, and cellulase), ammonia production, and zinc and phosphorus solubilization, all of which showed positive results, confirming its growth-promoting attributes. Besides, an in vivo experiment was conducted under controlled greenhouse conditions by withholding irrigation until soil moisture dropped to ~ 45% field water capacity (FWC) for 15 days. Four treatments are used: (1) well-watered control (90% field water capacity, FWC), (2) T. harzianum-inoculated under well-watered conditions, (3) drought-stressed (45% FWC), and (4) T. harzianum-inoculated+ drought-stressed. After 15 days of drought application, morphological (shoot height, in addition shoot and root fresh and dry weights), physiological (Chl a and b, relative water content [RWC], and membrane stability index [MSI]) and biochemical (osmolytes [proline, proteins and total soluble sugars] and antioxidant enzyme activities) assessments were recorded. The results indicated that shoot (39.44 and 37.92%) and root (10.29 and 28.77%) fwt and dwt, leaf RWC (7.90%), total pigment content (24.49%) and MSI (9.40%) decreased in drought-stressed maize while an increase in their membrane lipid peroxidation (77.21%), electrolyte leakage (EL) (48.04%) and hydrogen peroxide (128.94%) contents were noted versus the control plants; however, T. harzianum-treated plants showed the reverse responses. T. harzianum-treated maize plants revealed significant boosts in growth and physiology under stress paralleled to untreated ones, along with a notable enhancement in antioxidant defense activity (21.20 and 8.53% for POD and APX). Moreover, under stress, osmoprotectants, including proline (23.78%) and soluble sugars (12.28%) were markedly greater in Trichoderma- inoculated plants than non-inoculated. Our results recommend that T. harzianum is an effective, sustainable biotechnological tool for drought resilience in maize. Therefore, exploring and optimizing the application of T. harzianum addresses the broader goals of resource recycling, environmental sustainability, and climate-smart agriculture. Drought stress (45% field water capacity, FWC) considerably impaired maize growth and photosynthetic pigments (Chl a, Chl b, as well as carotenoids). Relative water content and membrane stability index of maize dropped under drought, indicating severe dehydration and osmotic imbalance. However, T. harzianum application reverses these detrimental effects on morphology and physiology. Under drought, stress markers (H2O2 and MDA, membrane injury in addition to electrolyte leakage) increased, confirming enhanced lipid peroxidation and cellular damage. T. harzianum inoculation enhanced osmolyte levels (proline, total soluble proteins and sugars), assisting osmotic adjustment. T. harzianum application upregulated antioxidant enzymes (APX, PPO, and POD), alleviating oxidative stress and improving drought tolerance.