A quantitative PCR assay for detection of the mycotoxigenic plant pathogen and food spoiling mold Paecilomyces niveus in fruit, food, and soil

The postharvest fruit pathogen Paecilomyces niveus produces ascospores that can survive some pasteurization temperatures, spoil fruit products, and contaminate them with patulin, an FDA-regulated mycotoxin. Preventing P. niveus from entering food systems requires a robust detection method to effectively determine sources of P. niveus spoilage and disease inoculum. We designed a new robust and culture-independent detection method using species-specific primers (PnPATf/r) based on the patK gene, encoding a 6-methylsalicylic acid synthase, in P. niveus, for use in a rapid qPCR assay. Primer specificity was validated using 24 different P. niveus isolates and 16 other important food spoilage and fruit pathogenic fungi. The threshold for detection of qPCR was 18 genome equivalents. To further validate our new detection method, we demonstrate its use in detecting P. niveus in infected fruits, infested soils and ciders, and in fruit arising from apple blossoms sprayed with a P. niveus spore suspension. Results from this study may help fruit producers address spoilage and patulin contamination by this food spoiling fungus. HighlightsO_LINew primers specific to Paecilomyces niveus (PnPATf/r) were developed based on the patK gene C_LIO_LIA qPCR assay to detect P. niveus was validated, and shown to be able to detect quantities of P. niveus DNA as low as 18 genome equivalents C_LIO_LIThe new qPCR assay was used to investigate the ability of P. niveus ascospores to infect strawberry fruits and enter apple fruits through apple blossom infestation C_LI