Differential response to synthetic and natural antifungals by Alternaria tenuissima in wheat simulating media: Growth, mycotoxin production and expression of a gene related to cell wall integrity.

Alternaria spp. are major contaminants of wheat crops, causing both economic losses for producers and health risk for consumers due to the accumulation of toxic metabolites. The application of synthetic fungicides in the field may trigger mycotoxin accumulation, since fungistatic levels of those compounds might cause fungal responses to stress. Hence, new alternatives are needed for its control. The aim of this work was to compare the effects of a natural antifungal compound, the antifungal protein PgAFP, and a synthetic commercial one, on Alternaria tenuissima sp.-grp. growth, mycotoxin biosynthesis (tenuazonic acid and alternariols) and the expression of a stress-related gene associated with cell wall integrity (CWI) pathway, in a wheat-based medium at two water activities (aw; 0.95 and 0.98 aw) conditions associated with the ripening of this grain. The application of both antifungals produced comparable fungistatic effects on Alternaria spp. growth. However, the presence of PgAFP produced a significant reduction in mycotoxins accumulation, whereas this effect was not observed with the commercial antifungal. To our knowledge, this is the first study on the influence of fungicides on the expression of a key gene involved in CWI stress-related pathway in relation to Alternaria mycotoxins accumulation. This information is useful when developing new antifungal methods for foods. The application of PgAFP would be a promising natural strategy for its application in wheat for the control of Alternaria spp.