Role of Trichoderma spp. in mitigating water deficiency and promoting Eucalyptus urophylla growth

Trichoderma spp. induce physiological and biochemical changes in plants, potentially enhancing growth and mitigating water deficit effects. This study evaluated morphophysiological parameters, water status indicators, gas exchange, and biochemical and metabolic responses of Eucalyptus urophylla under different water regimes and inoculation with T. asperellum and T. harzianum, as well as their impact on early field growth. A greenhouse experiment followed a 3 × 2 factorial design: three inoculation treatments (T. asperellum [TA], T. harzianum [TH], and control [C]) and two water regimes-water deficit (30% pot capacity) and well-irrigated (90% pot capacity). Morphophysiological traits, water status, gas exchange, and metabolic parameters were assessed. Additionally, three independent field experiments tested inoculation effects, with 250 seedlings per treatment planted at 2.5 × 3.5 m spacing. The effective experimental area comprised 60 central plots per treatment. Plant height, leaf number, and stem diameter were measured at 90 days post-transplant, while photosynthetic pigments, sugars (total, reducing, and soluble), starch, and proline were analyzed at 270 days. Water deficit reduced plant growth, leaf water potential, relative water content, and gas exchange while increasing thiobarbituric acid-reactive substances and hydrogen peroxide levels. Inoculation with T. asperellum and T. harzianum did not alleviate water deficit-induced growth reduction. However, regardless of the water regime, inoculation enhanced photosynthetic activity, water-use efficiency, and soluble sugarsand amino acid accumulation. Under field conditions, inoculated plants exhibited greater height, stem diameter, and leaf number but lower reducing sugars, soluble sugars, and starch levels compared to control plants.