Valorization of native rhizospheric vineyards’ fungi to enhance sustainable biocontrol against Downy Mildew in Tunisia

Lobna Hajji-Hedfi, Bassem Ayman Balbool, Abdelhak Rhouma, Akram Hassan, Samar Dali, Rocco Perniola & Ahmed M. Abdel Azeem

Sydowia 77: 161-176

Published online on November 21st, 2024

High Tunisian grape yield demands alternative controls for fungal disease Plasmopara viticola due to fungicide cost, environmental impact, and resistance emergence. In arid Tunisian vineyards (n=32), this study investigates the isolation, diversity, and characterization of rhizospheric fungi for potential downy mildew biocontrol. Fungal isolates are assessed for plant growth promotion traits (enzymes, nutrient solubilization, IAA, siderophore production) and antifungal activity against P. viticola. This study isolated a diverse fungal community from 32 sites (total 42 species, 59020 colony-forming units). Aspergillaceae dominated (14 spp., highest species-genus ratio), with Aspergillus niger being the most abundant isolate (11.54 %). Other recovered fungi included Penicillium (6 spp.), Fusarium (3 spp.), and Mucorales (3 spp.). Notably, Oomycota and teleomorphic Ascomycota were less prevalent. Fungal density positively correlated with water content, soil organic matter, and organic carbon, but decreased with potassium content. Among tested fungi, Trichoderma virens and T. harzianum displayed the most effective biocontrol against P. viticola, significantly reducing disease severity (21.87 and 20.33 %, respectively) and enhancing both inhibitory (69.99– 71.03 %, respectively) and protective potential (75.77–77.46 %, respectively) on grapevine leaves. T. virens and T. harzianum displayed the most desirable biocontrol traits. They produced the highest number of extracellular enzymes (6) and plant growthpromoting factors (5), including IAA. Both fungi tolerated a wide temperature range (19–30 °C) and pH (5–7) for growth.

Keywords: Rhizospheric fungi, Plasmopara viticola, Vineyards, Sustainable agriculture.

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