Isolation and identification of three new mycoparasites of Erysiphe necator for biological control of grapevine powdery mildew

Abstract

Powdery mildew causes significant yield and quality loss in grapes. Disease management includes fungicides belonging to the demethylation inhibitor and quinone outside inhibitor groups which are associated with development of fungicide resistant pathogen populations and detection of fungicide residues at harvest. This study was conducted to identify potential antagonists which can be used solo or in integration with safer chemical. Three mycoparasitic fungi were isolated and evaluated for parasitism and biocontrol. Light and scanning electron microscopic analysis showed that the hyphae of mycoparasites grew over the powdery mildew colony forming a mycelial web over it, coiled around the conidiophores and conidia of E. necator, penetrated the conidia and caused their total collapse. Based on molecular identification, the mycoparasites were identified as Lecanicillium antillanum, Acremonium sclerotigenum and Sarocladium terricola. All three isolates were positive for production of β-1-3 glucanase, cellulase, chitinase, protease, amylase and lipase which are involved in bio-control mechanism. During pot, nursery and vineyard trials all the isolates consistently showed powdery mildew reduction and achieved 41.76% to 65.61% disease reduction. Sarocladium terricola was more effective in all the trials. All three mycoparasites were compatible with chitosan and sulfur and alternate applications of mycoparasites with these two safe chemicals, the efficiency of L. antillanum, A. sclerotigenum and S. terricola was increased by 20.16, 27.33, and 8.94% respectively on leaves and 20.85, 21.36, and 16.06% respectively on bunches as compared to their solo applications. The study introduces new possibilities for control of grape powdery mildew using safer alternatives.