Improved physiological responses and stress tolerance in cotton against Fusarium wilt with Trichoderma harzianum treatment

Cotton is a vital cash crop in the agricultural economy. Many abiotic stresses and pathogenic diseases reduce cotton yield, with cotton wilt being a major threat caused by Fusarium oxysporum f.sp. vasinfectum (FOV). In the present study, the antagonistic potential of Trichoderma harzianum, along with its extracted volatile and non-volatile compounds, was evaluated against FOV. In a dual culture assay, T. harzianum showed 71.4% inhibition of FOV. The volatile compounds extracted from T. harzianum showed 54.9% inhibition of FOV, while the non-volatile compounds reduced the growth of F. oxysporum f.sp. vasinfectum by 64.21%. The evaluation of vegetative traits of cotton plants indicated increased biomass when treated with T. harzianum. The activity of antioxidant defense enzymes Catalase activity (CAT), Superoxide dismutase activity (SOD), and Peroxidase activity (POX) was highest in cotton plants treated with both T. harzianum and F. oxysporum f.sp. vasinfectum, indicating an activation of the plant defense mechanisms in response to these treatments. Protein content, Malondialdehyde Content (MDA), proline content, electrolyte leakage, and H2O2 content, which are stress markers, were at their maximum under F. oxysporum f.sp. vasinfectum stress. Physiological features, including stomatal conductance, photosynthesis rate, Soil Plant Analysis Development (SPAD) chlorophyll value, and relative water content, were highest in plants treated with T. harzianum, as T. harzianum improves and boosts plant growth. Hence, T. harzianum is an effective biological control agent against FOV.