Interactions between cranberries and fungi: the proposed function of organic acids in virulence suppression of fruit rot fungi

Abstract

Cranberry fruit are a rich source of bioactive compounds that may function as constitutive or inducible barriers against rot-inducing fungi. The content and composition of these compounds change as the season progresses. Several necrotrophic fungi cause cranberry fruit rot disease complex. These fungi remain mostly asymptomatic until the fruit begins to mature in late August. Temporal fluctuations and quantitative differences in selected organic acid profiles between fruit of six cranberry genotypes during the growing season were observed. The concentration of benzoic acid in fruit increased while quinic acid decreased throughout fruit development. In general, more rot-resistant genotypes (RR) showed higher levels of benzoic acid early in fruit development and more gradual decline in quinic acid levels than that observed in the more rot-susceptible genotypes. We evaluated antifungal activities of selected cranberry constituents and found that most bioactive compounds either had no effects or stimulated growth or reactive oxygen species (ROS) secretion of four tested cranberry fruit rot fungi, while benzoic acid and quinic acid reduced growth and suppressed secretion of ROS by these fungi. We propose that variation in the levels of ROS suppressive compounds, such as benzoic and quinic acids, may influence virulence by the fruit rot fungi. Selection for crops that maintain high levels of virulence suppressive compounds could yield new disease resistant varieties. This could represent a new strategy for control of disease caused by necrotrophic pathogens that exhibit a latent or endophytic phase.

Mixed Phenolic Acids Mediated Proliferation of Pathogens Talaromyces helicus and Kosakonia sacchari in Continuously Monocultured Radix pseudostellariae Rhizosphere Soil

“…B. pumilus is a PGPR, which has been successfully used for the biological control of damping-off diseases (Huang et al, 2012 ). Tadych et al ( 2015 ) also proposed quinic acids could significantly influence virulent facctors of the fruit rot fungi. In our studies, the 3A-DON toxin production of the pathogenic, T. helices , can be promoted by some phenolic acids, especially by the phenolic acids mixed in the same ratio as detected in monocultured rhizosphere soil, then a cascade reaction was triggered off to promote the growth of the other pathogenic fungus, K. sacchari and inhibited the growth of its counterpart, the beneficial bacterium, B. pumilus , (Figure S4 ).…”

Endosymbionts in cranberry: Diversity, effect on plant growth, and pathogen biocontrol

“…To fill the knowledge gap on both fungal and bacterial ericoid endosymbionts, Vaccinium macrocarpon Aiton (American cranberry) is a plant model of choice (Sauer et al, 2002; Tadych et al, 2012, 2015). This experimental system combines several advantages: (i) the perennial plant can be easily propagated by cuttings or seeds; (ii) endosymbiont‐free plants can be readily generated, allowing controlled growth and biocontrol experiments; and (iii) being an important crop species in Northern America, there is great interest in translational research.…”

Nature Abhors a Vacuum: Highly Diverse Mechanisms Enable Spoilage Fungi to Disperse, Survive, and Propagate in Commercially Processed and Preserved Foods

“…The ability to withstand acidic insults is also a virulence factor among endophytic plant pathogens. Some endophytic fungi grow symbiotically within immature fruits that contain high levels of weak organic acids (Tadych et al., ). In fact, the presence of weak organic acids may suppress necrotrophy until acid levels decrease as the fruit matures and the disease develops.…”