Biology subjects

Wang, T. W.

Publications and source records attributed to Wang, T. W..

3 recordsLinked to original sources

bioRxiv2023

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

microbiology↗

bioRxiv2023

Patulin contamination of hard apple cider by Paecilomyces niveus and other postharvest apple pathogens: assessing risk factors

Hard apple cider is considered to be a low-risk product for food spoilage and mycotoxin contamination due to its alcoholic nature and associated food sanitation measures. However, the thermotolerant mycotoxin-producing fungus Paecilomyces niveus may pose a significant threat to hard cider producers. Pa. niveus is known to infect apples (Malus xdomestica), and previous research indicates that it can survive thermal processing and contaminate finished apple juice with the mycotoxin patulin. To determine if hard apple cider is susceptible to a similar spoilage phenomenon, cider apples were infected with Pa. niveus or one of three patulin-producing Penicillium species and the infected fruits underwent benchtop fermentation. Cider was made with lab inoculated Dabinett and Medaille dOr apple cultivars, and patulin was quantified before and after fermentation. Results show that all four fungi can infect cider apples and produce patulin, some of which is lost during fermentation. Only Pa. niveus was able to actively grow throughout the fermentation process. To determine if apple cider can be treated to hinder Pa. niveus growth, selected industry-grade sanitation measures were tested, including chemical preservatives and pasteurization. High concentrations of preservatives inhibited Pa. niveus growth, but apple cider flash pasteurization was not found to significantly impact spore germination. This study confirms that hard apple cider is susceptible to fungal-mediated spoilage and patulin contamination. Pa. niveus should be of great concern to hard apple cider producers due to its demonstrated thermotolerance, survival in fermentative environments, and resistance to sanitation measures. HighlightsO_LIApple fruits of traditional cider cultivars Dabinett and Medaille dOr were found to be susceptible to infection by three patulin-producing Penicillium spp. and Paecilomyces niveus C_LIO_LIPa. niveus can grow in finished fermented hard cider at 5.22% ethanol C_LIO_LIPatulin levels in cider were reduced by fermentation but still exceeded 50 {micro}g/kg, a maximum limit set by various regulatory agencies C_LIO_LIPa. niveus was observed to be able to grow in low concentrations of three preservatives: potassium sorbate, sulfur dioxide, and sodium benzoate C_LI

microbiology↗

bioRxiv2021

Susceptibility of rosaceous fruits and apple cultivars to postharvest rot by Paecilomyces niveus

Paecilomyces rot of apples is a postharvest disease caused by Paecilomyces niveus, a problematic spoiling agent of fruit juices and derivatives. The fungus produces ascospores that can survive food processing and germinate in finished fruit products. Processing apple fruits infected with Paecilomyces rot can lead to P. niveus contaminated juices. Because the fungus produces the mycotoxin patulin, juice spoilage by P. niveus is an important health hazard. Little is known about the disease biology and control mechanisms of this recently described postharvest disease. Following Kochs postulates, we determined that a range of previously untested rosaceous fruits and popular apple cultivars are susceptible to Paecilomyces rot infection. We also observed that two closely related food spoiling fungi, Paecilomyces fulvus and Paecilomyces variotti, were unable to infect, cause symptoms in, or reproduce in wounded fruits. Our results highlight the unique abilities of Paecilomyces niveus to infect a variety of fruits, produce patulin, and form highly-resistant spores capable of spoiling normally shelf-stable products.

pathology↗