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

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.

Foliar application of the leaf-colonizing yeast Pseudozyma churashimaensis elicits systemic defense of pepper against bacterial and viral pathogens

“…3). Leaf application of Pseudozyma aphidis induced systemic resistance against the bacterial canker pathogen Clavibacter michiganensis on tomato, the powdery mildew fungus Podosphaera xanthii on cucumber, and the gray mold pathogen Botrytis cinerea on Arabidopsis thaliana 3536. However, the authors demonstrated direct inhibition of target pathogen growth by P. aphidis crude extract.…”

“…The mechanism of postharvest biological control was proposed to include induction of host defense, pathogen antagonism due to lytic enzyme secretion, alleviation of oxidative damage, and biofilm formation49. Only recently, some studies reported that foliar spray of epiphytic yeast protects tomato, cucumber, and potato plants against fungal and bacterial pathogens34353650.…”

“…Induced resistance was confirmed by gene expression priming analysis of PR1 and PDF1.2 in Arabidopsis 34. The defense signaling for the P. aphidis -mediated induced resistance was elicited through pathways that were dependent on jasmonic acid (JA) and salicylic acid (SA) signaling but independent of ethylene signaling3536. Pre-treatment spraying of tomato and cucumber plants with Podosphaera xanthii spores suppressed bacterial canker (caused by Clavibacter michiganensis ) and powdery mildew (caused by Podosphaera xanthii ).…”

“…Pre-treatment spraying of tomato and cucumber plants with Podosphaera xanthii spores suppressed bacterial canker (caused by Clavibacter michiganensis ) and powdery mildew (caused by Podosphaera xanthii ). Further analysis revealed that extracellular metabolites from P. aphidis directly inhibited C. michiganensis growth and P. xanthii spore germination; therefore, this cannot be classified as induced resistance3536.…”

Molecular identification of Pseudozyma aphidis (Henninger & Windisch) Boekhout: first record from a Brazilian mangrove swamp

“…This genus has been isolated from different types of materials such as leaves (Golubev et al 2007, Chamnanpa et al 2013, flowers (Wei et al 2005, Liou et al 2009), blood samples (Sugita et al 2003, Mekha et al 2014) and even associated with coral reefs and insects (Henninger & Windisch 1975, StatzellTallman et al 2010, Oliveira et al 2014. Pseudozyma aphidis (Henninger & Windisch) Boekhout was firstly described as Sterigmatomyces aphidis Henninger & Windisch in Germany and isolated from Aphididae secretions on leaves of Solanum pseudocapsieum (Henninger & Windisch 1975).…”