Soil application of Trichoderma asperellum strains significantly improves Fusarium root and stem rot disease management and promotes growth in cucumbers in semi-arid regions

To improve biocontrol approaches in Saudi Arabia, it is necessary to collect and screen suitable native Trichoderma strains. In this study, the biocontrol potential of 20 native Trichoderma asperellum strains was assessed using dual culture and antibiosis assays against Fusarium oxysporum f. sp. radicis-cucumerinum (Forc), the causal agent of Fusarium root and stem rot (FRSR) in cucumber plants. We identified two T. asperellum strains (TAS23 and TAS27) with the highest in vitro antagonistic capacity against Forc. The compatibility between the two strains was identified in vitro. We found that treating cucumber plants with these antagonistic strains separately was effective in delaying the occurrence of FRSR in greenhouse trials. However, treatment with strain mixture TASMix (TAS23 + TAS27) had a synergistic effect and resulted in the highest reduction (P < 0.05) in disease incidence and severity index by 51% and 59.6%, respectively. The decrease in growth due to pathogen-induced stress was significantly less in the TASMix-treated plants than in those treated with individual strains. Real-time PCR assay revealed that the reduction of FRSR in plants treated with TASMix was accompanied by a significant reduction in Forc populations in cucumber stems and rhizosphere. The results of this study suggest that TASMix-controlled FRSR is achieved by reducing reactive oxygen species accumulation, limiting cellular damage, and increasing the activities of antioxidant enzymes in cucumber roots. In summary, a synergistic approach with the application of a mixture of native Trichoderma strains seems promising for managing FRSR in cucumber under organic farming conditions in semi-arid regions.

Automated summary

This study evaluated the biocontrol potential of 20 native Trichoderma asperellum strains against Fusarium root and stem rot (FRSR) in cucumber plants. Two strains (TAS23 and TAS27) showed the highest antagonistic capacity and their mixture (TASMix) had a synergistic effect, significantly reducing disease incidence and severity in greenhouse trials. The reduction in FRSR was accompanied by a decrease in pathogen populations and improved plant growth.