Humans and animals are exposed to aflatoxins, toxic carcinogenic fungal metabolites, through consumption of contaminated food and feed. Aspergillus flavus , the primary causal agent of crop aflatoxin contamination, is composed of phenotypically and genotypically diverse vegetative compatibility groups (VCGs). Molecular data suggest that VCGs largely behave as clones with certain VCGs exhibiting niche preference. VCGs vary in aflatoxin‐producing ability, ranging from highly aflatoxigenic to atoxigenic. The prevalence of individual VCGs is dictated by competition during growth and reproduction under variable biotic and abiotic conditions. Agronomic practices influence structures and average aflatoxin‐producing potentials of A. flavus populations and, as a result, incidences and severities of crop contamination. Application of atoxigenic strains has successfully reduced crop aflatoxin contamination across large areas in the United States. This strategy uses components of the endemic diversity to alter structures of A. flavus populations and improve safety of food, feed, and the overall environment.
This report identifies an Alternaria disease affecting pinto beans in incidence in Arizona. The similarity of disease symptoms and morphology of the pathogen to a recently characterized Alternaria and its disease of bean in Brazil causes concern about its potentially damaging effects on pinto bean production in Arizona. Accepted for publication 20 September 2011. Published 18 October 2011.
Bird species worldwide are affected by trichomoniasis caused by the protist Trichomonas gallinae. In avivorous raptors such as Cooper's hawks (Accipiter cooperii), nestlings are more susceptible than fledglings and adults. Previous research suggested a link between oral pH and susceptibility: the oral pH of fledgling and adult hawks is more than seven times more acidic than that of nestlings. We speculated that this age-specific difference in pH would correspond to age-specific differences in the oral microbiota of Cooper's hawks. We examined the oral microbiomes of 31 healthy, wild Cooper's hawks in Tucson, Arizona (USA). Individuals represented three age classes (nestlings, fledglings, and adults). We designed our study with multiple controls, replicated sampling, mock communities, and stringent quality-controls to address challenges that can limit the inferential quality of microbiome data sets.Richness of bacterial communities in oral cavities of Cooper's hawks differed as a function of age but not as a function of sex, sampling date, or sampling location. Bacterial communities in oral cavities of nestlings differed from those of fledglings and adults, whereas communities in fledglings and adults did not differ from each other. Communities were similar in males and females and did not differ over the sampling season. Prevalence of acid-producing bacteria in fledgling and adults vs. nestlings is consistent with previous reports of age-specific variation in oral pH, but further research is needed to establish a causal link to pH levels or susceptibility to disease. Analyses of mock communities demonstrated high repeatability and showed that operon number and read abundance were highly correlated.The oral microbiota of wild Cooper's hawks differs between nestlings and older birds. Variation in the oral microbiome is consistent with differences in oral pH between nestlings and older individuals. Overall our study provides a first perspective on bacterial communities associated with oral cavities of a wild raptor.
Biodiversity collections contain a wealth of information encapsulated both in specimens and in their metadata, providing the foundation for diverse studies in fields such as ecology. Yet biodiversity repositories can present a challenge for ecological inferences because collections rarely are structured with ecological questions in mind: collections may be opportunistic in space or time, may focus on particular taxonomic groups, may reflect different collection strategies in different places or times, or may not be exhaustive in terms of retaining every specimen or having similar metadata for each record. In addition to its primary holdings, the Robert L. Gilbertson Mycological Herbarium at the University of Arizona holds a collection of living specimens of fungi isolated from the interior of healthy plants and lichens (i.e., endophytic and endolichenic fungi). Over the past decade, more than 7000 isolates from the southwestern United States were accessioned, including strains from diverse hosts in more than 50 localities across the biotically rich state of Arizona. This collection is distinctive in that metadata and barcode sequences are available for each specimen, many localities have been sampled with consistent methods, and all isolates obtained in surveys have been retained. Here, we use this herbarium collection to examine endophyte community structure in an ecological and evolutionary context. We then artificially restructure the collection to resemble collections more typical of biodiversity repositories, providing a case study for ecological insights that can be gleaned from collections that were not structured explicitly to address ecological questions. Overall, our analyses highlight the relevance of biogeography, climate, hosts, and geographic separation in endophyte community composition. This study showcases the importance of extensive metadata in collections and highlights the utility of biodiversity collections that can yield emergent insights from many surveys to answer ecological questions in mycology, ultimately providing information for understanding and conserving fungal biodiversity.
In the Rio Grande Valley of Texas (RGV), values of maize and cottonseed crops are significantly reduced by aflatoxin contamination. Aflatoxin contamination of susceptible crops is the product of communities of aflatoxin producers and the average aflatoxin-producing potentials of these communities influence aflatoxin contamination risk. Cropping pattern influences community composition and, thereby, the epidemiology of aflatoxin contamination. In 2004, Aspergillus parasiticus was isolated from two fields previously cropped to sugarcane but not from 23 fields without recent history of sugarcane cultivation. In 2004 and 2005, A. parasiticus composed 18 to 36% of Aspergillus section Flavi resident in agricultural soils within sugarcane-producing counties. A. parasiticus was not detected in counties that do not produce sugarcane. Aspergillus section Flavi soil communities within sugarcane-producing counties differed significantly dependent on sugarcane cropping history. Fields cropped to sugarcane within the previous 5 years had greater quantities of A. parasiticus (mean = 16 CFU/g) than fields not cropped to sugarcane (mean = 0.1 CFU/g). The percentage of Aspergillus section Flavi composed of A. parasiticus increased to 65% under continuous sugarcane cultivation and remained high the first season of rotation out of sugarcane. Section Flavi communities in fields rotated to non-sugarcane crops for 3 to 5 years were composed of <5% A. parasiticus, and fields with no sugarcane history averaged only 0.2% A. parasiticus. The section Flavi community infecting RGV sugarcane stems ranged from 95% A. parasiticus in billets prepared for commercial planting to 52% A. parasiticus in hand-collected sugarcane stems. Vegetative compatibility assays and multilocus phylogenies verified that aflatoxin contamination of raw sugar was previously attributed to similar A. parasiticus in Japan. Association of closely related A. parasiticus genotypes with sugarcane produced in Japan and RGV, frequent infection of billets by these genotypes, and the ephemeral nature of A. parasiticus in RGV soils suggests global transport with sugarcane planting material.
Table S2. Mock community, number of operons, and average reads observed for the even and staggered mock communities. Table containing details for each mock community. (XLSX 56 kb)
Table S1. Summary of operational taxonomic units for oral microbiome of urban Cooperâ s hawks. Excel file containing operational taxonomic units, taxonomy, and occurrence of each in individual hawks. (XLSX 115 kb)
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