AUTHOR=Gafni Aviva , Calderon Claudia E. , Harris Raviv , Buxdorf Kobi , Dafa-Berger Avis , Zeilinger-Reichert Einat , Levy Maggie 

TITLE=Biological control of the cucurbit powdery mildew pathogen Podosphaera xanthii by means of the epiphytic fungus Pseudozyma aphidis and parasitism as a mode of action

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00132

DOI=10.3389/fpls.2015.00132

ISSN=1664-462X

ABSTRACT=<p>Epiphytic yeasts, which colonize plant surfaces, may possess activity that can be harnessed to help plants defend themselves against various pathogens. Due to their unique characteristics, epiphytic yeasts belonging to the genus <italic>Pseudozyma</italic> hold great potential for use as biocontrol agents. We identified a unique, biologically active isolate of the epiphytic yeast <italic>Pseudozyma aphidis</italic> that is capable of inhibiting <italic>Botrytis cinerea</italic> via a dual mode of action, namely induced resistance and antibiosis. Here, we show that strain L12 of <italic>P. aphidis</italic> can reduce the severity of powdery mildew caused by <italic>Podosphaera xanthii</italic> on cucumber plants with an efficacy of 75%. Confocal and scanning electron microscopy analyses demonstrated <italic>P. aphidis</italic> proliferation on infected tissue and its production of long hyphae that parasitize the powdery mildew hyphae and spores as an ectoparasite. We also show that crude extract of <italic>P. aphidis</italic> metabolites can inhibit <italic>P. xanthii</italic> spore germination <italic>in planta</italic>. Our results suggest that in addition to its antibiosis as mode of action, <italic>P. aphidis</italic> may also act as an ectoparasite on <italic>P. xanthii</italic>. These results indicate that <italic>P. aphidis</italic> strain L12 has the potential to control powdery mildew.</p>