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Paecilomyces rot of apples is a postharvest disease caused by Paecilomyces niveus, a problematic spoiling agent of fruit juices and derivatives. Processing fruits infected with Paecilomyces rot can lead to juices contaminated with P. niveus ascospores. These ascospores are heat resistant and may survive food processing and germinate in finished products. 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. The range of fruit products contaminated by P. niveus and patulin led us to hypothesize that the host range of Paecilomyces rot is broader than previously thought. Following Koch’s postulates, we determined that multiple untested rosaceous fruits and popular apple cultivars are susceptible to Paecilomyces rot infection and that these infected fruits contain significant levels of patulin. We also observed that two closely related food spoiling fungi, Paecilomyces fulvus and Paecilomyces variotti, were unable to infect, cause symptoms in, or grow in wounded fruits. Therefore, we challenge the assumption that P. niveus spoilage inoculum is introduced to foods solely through environmental sources, and we show that other economically important rosaceous fruits, peaches, pears, sweet cherries, and sour cherries, are susceptible to infection and can also be sources of spoilage inoculum. Our results highlight the unique abilities of P. niveus to infect a variety of fruits, produce patulin, and form resistant spores capable of spoiling normally shelf-stable products.

The postharvest fruit pathogenPaecilomyces niveusproduces ascospores that can survive some pasteurization temperatures, spoil fruit products, and contaminate them with patulin, an FDA-regulated mycotoxin. PreventingP. niveusfrom entering food systems requires a robust detection method to effectively determine sources ofP. niveusspoilage 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, inP. niveus, for use in a rapid qPCR assay. Primer specificity was validated using 24 differentP. niveusisolates 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 detectingP. niveusin infected fruits, infested soils and ciders, and in fruit arising from apple blossoms sprayed with aP. niveusspore suspension. Results from this study may help fruit producers address spoilage and patulin contamination by this food spoiling fungus.HighlightsNew primers specific toPaecilomyces niveus(PnPATf/r) were developed based on the patK geneA qPCR assay to detectP. niveuswas validated, and shown to be able to detect quantities ofP. niveusDNA as low as 18 genome equivalentsThe new qPCR assay was used to investigate the ability ofP. niveusascospores to infect strawberry fruits and enter apple fruits through apple blossom infestation

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 fungusPaecilomyces niveusmay pose a significant threat to hard cider producers.Pa. niveusis known to infect apples (Malusxdomestica), 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 withPa. niveusor one of three patulin-producingPenicilliumspecies and the infected fruits underwent benchtop fermentation. Cider was made with lab inoculated Dabinett and Medaille d’Or 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. OnlyPa. niveuswas able to actively grow throughout the fermentation process. To determine if apple cider can be treated to hinderPa. niveusgrowth, selected industry-grade sanitation measures were tested, including chemical preservatives and pasteurization. High concentrations of preservatives inhibitedPa. niveusgrowth, 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. niveusshould be of great concern to hard apple cider producers due to its demonstrated thermotolerance, survival in fermentative environments, and resistance to sanitation measures.HighlightsApple fruits of traditional cider cultivars Dabinett and Medaille d’Or were found to be susceptible to infection by three patulin-producingPenicilliumspp. andPaecilomyces niveusPa. niveuscan grow in finished fermented hard cider at 5.22% ethanolPatulin levels in cider were reduced by fermentation but still exceeded 50 µg/kg, a maximum limit set by various regulatory agenciesPa. niveuswas observed to be able to grow in low concentrations of three preservatives: potassium sorbate, sulfur dioxide, and sodium benzoate

Paecilomyces rot of apples is a postharvest disease caused by

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 Koch’s 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.

Desiccation tolerance was a key trait that allowed plants to colonize land. However, little is known about the transition from desiccation tolerant non-vascular plants to desiccation sensitive vascular ones. Filmy ferns (Hymenophyllaceae) represent a useful system to investigate how water-stress strategies differ between non-vascular and vascular stages within a single organism because they have vascularized sporophytes and nonvascular gametophytes that are each capable of varying degrees of desiccation tolerance. To explore this, we surveyed sporophytes and gametophytes of 19 species (22 taxa including varieties) of filmy ferns on Moorea (French Polynesia) and used chlorophyll fluorescence to measure desiccation tolerance and light responses. We conducted phylogenetically informed analyses to identify differences in physiology between life stages and growth habits. Gametophytes had similar or less desiccation tolerance (ability to recover from 2 days desiccation at - 86 MPa) and lower photosynthetic optima (maximum electron transport rate of photosystem II and light level at 95% of that rate) than sporophytes. Epiphytes were more tolerant of desiccation than terrestrial species in both life stages. Despite their lack of greater physiological tolerances, gametophytes of several species occurred over a wider elevational range than conspecific sporophytes. Our results demonstrate that filmy fern gametophytes and sporophytes differ in their physiology and niche requirements, and point to the importance of microhabitat in shaping the evolution of water-use strategies in vascular plants.

Desiccation tolerance was a key trait that allowed plants to colonize land. However, little is known about the transition from desiccation tolerant non-vascular plants to desiccation sensitive vascular ones. Filmy ferns (Hymenophyllaceae) represent a useful system to investigate how water-stress strategies differ between non-vascular and vascular stages within a single organism because they have vascularized sporophytes and nonvascular gametophytes that are each capable of varying degrees of desiccation tolerance. To explore this, we surveyed sporophytes and gametophytes of 19 species (22 taxa including varieties) of filmy ferns on Moorea (French Polynesia) and used chlorophyll fluorescence to measure desiccation tolerance and light responses. We conducted phylogenetically informed analyses to identify differences in physiology between life stages and growth habits. Gametophytes had similar or less desiccation tolerance (ability to recover from 2 d desiccation at -86 MPa) and lower photosynthetic optima (maximum electron transport rate of photosystem II and light level at 95% of that rate) than sporophytes. Epiphytes were more tolerant of desiccation than terrestrial species in both life stages. Despite their lack of greater physiological tolerances, gametophytes of several species occurred over a wider elevational range than conspecific sporophytes. Our results demonstrate that filmy fern gametophytes and sporophytes differ in their physiology and niche requirements, and point to the importance of microhabitat in shaping the evolution of water-use strategies in vascular plants.

Paecilomyces niveus is a heat-resistant mold that can spoil fruit products including orange juice, potentially introducing the regulated mycotoxin patulin. The authors hypothesize this fungus may enter orange juice through infected fruits. This study confirms P. niveus can be a wound-infecting pathogen of both oranges and clementines.

Paecilomyces niveus is an extremotolerant fungus with surprising powers to survive high temperatures and infect apples and aphids. These abilities make it a formidable enemy in food and agricultural environments. In addition, it produces patulin, the most significant mycotoxin in apples.

The introduction of non-native animals occasionally results in the co-introduction of their microbial symbionts or parasites. The trade of exotic pets and zoo animals has inadvertently introduced several parasitic species to countries where they are non-native. Both the presence of suitable native hosts and opportunity for dispersal determine whether these non-native species become naturalized. During our studies dealing with species of Herpomyces (Ascomycota, Laboulbeniomycetes), fungi that are exclusively ectoparasitic on cockroaches (Hexapoda, Blattodea), we make use of artificial colonies. Most of our specimens originate from pet stores and laboratory populations. Although they were originally intended for transmission studies, we discovered that some cockroaches from artificial colonies carried fruiting bodies of Herpomyces. We screened a total 292 cockroaches from 11 populations that we maintained after purchase. Sources were different pet stores, a toxicological laboratory, and a biological supply company. In eight populations, we found at least some Herpomyces-infected cockroaches. Parasite prevalence varied between 8.77% and 86.33%. Host associations were Blatta orientalis with Herpomyces stylopygae, Blattella germanica with H. ectobiae, Periplaneta americana with H. periplanetae, Phoetalia pallida with H. leurolestis, and Shelfordella lateralis with an undescribed species of Herpomyces. Apart from the new reports, host associations, and consequences for taxonomy (a new species based on morphological and molecular characters), we started to think about the geographic distributions of these fungi and how we, humans, shape them through spreading hosts and through international pet trade. We reviewed the currently known records of Herpomyces-associated cockroaches and host-parasite relationships. Based on the available data, on a global scale, at least half of the currently known species of Herpomyces are spread by globally invasive host species and through international pet trade. This indicates that the distribution and host range of these obscure and often unnoticed fungi are affected by human activities.

The consequences of initial variability in reproductive effort on later pollination and fruit development have frequently been investigated with flower removal experiments. Often, plants produce many fewer fruits than flowers, so flower removal might not be expected to alter subsequent growth or development patterns all that much. Yet, many studies have demonstrated such changes even for species with low average fruit set, which begs for an explanation. Many (at least seven, by our count) such explanations have been reported in the literature, but experimental support for most is limited. In summer 2014, we conducted a field experiment on a lowbush blueberry (Vaccinium angustifolium) farm in Maine. In this experiment, we coupled flower removal with three other treatments, each designed to assess the validity of one of three often-cited hypotheses invoked to explain why growth and development changes occur following flower removal: 1) “Short-term nutrient shortages;” 2) “spatiotemporal limitations;” and 3) “the compound interest effect.” The three respective treatments—foliar nitrogen fertilization, positionally biased flower removal, and defoliation—were designed to either intensify or weaken the apparent effects of flower removal if the corresponding hypothesis had merit. As in a 2013 preliminary experiment, flower removal elicited several statistically significant growth and development changes in blueberry, including increases in final leaf area, ripe fruit weight, fruit ripening rate, and relative fruit production. The additional treatments also elicited several significant plant responses, though not always with concomitant flower removal effects as well. For example, fertilization generally increased fruit cluster mass by harvest, but flower removal itself had no such effect on cluster mass. Most observed interactive effects between flower removal and the additional treatments either ran counter to expectations, were limited in scope, or couldn't be unambiguously interpreted. For at least a few observed changes, none of the additional treatments significantly altered the effects of flower removal. We conclude that current hypotheses for the mechanistic basis for changes induced by flower removal are inadequate, at least for blueberry, a species with frequently low fruit set even when managed commercially. However, strong intellectual and economic imperatives exist to encourage further investigation into this open question.Plants grown in horticulture or occurring as adventives outside their native range can provide insight into species’ fundamental niche requirements that might not be evident from the native range, or realized niche, alone. Such occurrences can also identify conditions that support individual survival, but do not currently sustain positive population growth (i.e., a species’ ‘tolerance niche’). Further, in the context of rapid climate change, horticultural and adventive occurrences beyond current range edges might circumvent natural dispersal limitations and facilitate species range shifts. To explore these concepts in the field, we investigated the history and structure of five newly discovered populations of naturalized Magnolia tripetala near horticultural sites in western Massachusetts, USA. This tree species is native to the southeastern US, but has been grown horticulturally in the Northeast since the 1800s. However, naturalized populations had not been well documented in the region previously, raising the possibility that the species’ escape has been triggered by recent climate change. With tree coring and life stage surveys, we asked whether the naturalized populations exhibited synchronous patterns of establishment and expansion, suggestive of climatic release and a shift from tolerance niche to fundamental niche conditions in the region. Across the five sites, we documented 660 individuals, with populations ranging in size from 46 to 396 individuals, including seedlings, saplings, and reproduct