Rhizospheric Trichoderma as multifunctional agents for controlling Pythium irregulare and enhancing strawberry plant growth

Abstract

Root rot caused by Pythium irregulare represents a major constraint in strawberry production, leading to significant losses in plant vigor and yield. The present study aimed to evaluate the biocontrol potential and plant growth–promoting activity of native rhizospheric Trichoderma isolates against this pathogen under in vitro , greenhouse, and field conditions. A total of 20 isolates were obtained from strawberry rhizosphere soils and identified through ITS rDNA and EF1-α gene sequencing, revealing five species, including Trichoderma virens, T. asperellum, T. asperelloides, T. hamatum and T. viride . Dual culture assays demonstrated that all isolates significantly inhibited the mycelial growth of P. irregulare , with inhibition rates ranging from 53.39 % to 79.33 %. The most effective strains, particularly T. virens (Tri3, Tri2) and T. viride (TriY), exhibited strong antagonistic activity. Volatile organic compounds (VOCs) produced by selected isolates reduced pathogen growth by up to 84.18 %, while culture filtrates showed inhibition rates reaching 78.94 %, indicating the contribution of both diffusible and volatile metabolites to pathogen suppression. Biochemical screening revealed that the most efficient isolates displayed strong hydrolytic enzyme activities, including cellulase, protease and Endo-1,4-β-glucanase, along with multiple plant growth promoting traits such as siderophore production, phosphate and potassium solubilization and auxin synthesis. Greenhouse assays confirmed the biocontrol efficacy of selected isolates, with T. virens Tri3 reducing disease severity to 16.6 %, followed by Tri2 (25 %) and T. viride TriY (37.5 %). Under field conditions, these isolates also significantly enhanced plant growth, improving biomass accumulation, chlorophyll content, and yield-related parameters compared to untreated controls. Overall, the results demonstrate the multifunctional potential of native Trichoderma isolates, particularly T. virens and T. viride , for both the suppression of P. irregulare and the control of strawberry root rot, while simultaneously promoting plant growth. These findings highlight their promise as sustainable alternatives to chemical control strategies.