Abstract
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 Pseudozyma hold great potential for use as biocontrol agents. We identified a unique, biologically active isolate of the epiphytic yeast Pseudozyma aphidis that is capable of inhibiting Botrytis cinerea via a dual mode of action, namely induced resistance and antibiosis. Here, we show that strain L12 of P. aphidis can reduce the severity of powdery mildew caused by Podosphaera xanthii on cucumber plants with an efficacy of 75%. Confocal and scanning electron microscopy analyses demonstrated P. aphidis 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 P. aphidis metabolites can inhibit P. xanthii spore germination in planta. Our results suggest that in addition to its antibiosis as mode of action, P. aphidis may also act as an ectoparasite on P. xanthii. These results indicate that P. aphidis strain L12 has the potential to control powdery mildew.
Highlights
Plant pathogens challenge our efforts to maximize crop production
Fungal biocontrol agents are important for disease control and can provide a viable alternative for chemical-based pesticides
The number of fungal biocontrol agents that are currently used for practical applications is minuscule as compared with the use of chemical-based agents
Summary
Plant pathogens challenge our efforts to maximize crop production. Constant selective pressures from multiple applications has led to the development of pathogens and pests that are resistant to chemical pesticides and efforts are being made to develop novel techniques and tools to control these pests and pathogens (Denholm and Rowland, 1992; Leroux et al, 2002). Among these tools, fungal biocontrol agents have attracted much attention as a viable and important alternative to conventional pesticides.
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