Wild Yeast Strains as Prospective Candidates to Induce Resistance Against Potato Late Blight (Phytophthora infestans)

Abstract

The potential for crop destruction by Phytophthora infestans, the causal agent of the Late Blight of potato has not diminished since its impact led to the Irish potato famine. Potato production generally requires frequent applications of synthetic fungicides to hold this disease in check. As possible alternatives to fungicides, we investigated wild yeasts as bio-control agents. Ten strains of wild yeasts isolated from vineyards within Washington State were assessed for the ability to reduce effects of P. infestans in potato leaf assays, and for suppression of growth of selected plant pathogenic fungi in agar culture. Metschnidowia pulcherrima (Mp), Curibasidium pallidicorallinum (Cp), and Candida saitoana (Cs) strains applied to potato leaves prior to inoculation with P. infestans reduced symptoms in a manner suggestive of induced immunity. A narrow concentration range of Mp most favorably suppressed late blight symptoms. These and other wild yeast strains were shown to induce phytoalexin production in a pea system developed for monitoring nonhost resistance. Further work toward developing successful agricultural application of this biocontrol agent will require verification of resistance-inducing benefits under field conditions.