β-Carotene inhibition of aflatoxin biosynthesis amongAspergillus flavus genotypes from Illinois corn

Thirty-nineAspergillus flavus genotypes (DNA fingerprinting) isolated from corn grown in a field near Kilbourne, Illinois were evaluated for their sensitivity to β-carotene (50 μg/ml) inhibition of aflatoxin B₁ biosynthesis. Inhibition of aflatoxin was greater than 90% for 28 of the genotypes and >70% for 38 of the 39 genotypes. FiveA. flavus strains (4 fingerprint groups) isolated from molded raw peanuts, NRRL 3239, NRRL 3357, NRRL 6514, NRRL 6515 and NRRL 13135, produced greater quantities of aflatoxin than all 39 genotypes isolated from corn, and were less sensitive to β-carotene inhibition.Aspergillus flavus NRRL 3357 is commonly used as inoculum in variety trials for aflatoxin resistance. Isolate identity and sensitivity to potential inhibitors in corn can be critical in assessing corn resistance to aflatoxin.     

Characterization of aflatoxigenic and non-aflatoxigenic <Emphasis Type="Italic">Aspergillus flavus</Emphasis> isolates from pistachio

Pistachio is a popular snack food. Aflatoxin contamination of pistachio nuts is a serious problem for many producing countries. The development of biological control methods based on ecological parameters is an environmentally friendly approach. Thirty-eight Aspergillus flavus isolates collected from a pistachio orchard in California (CA) were analyzed for production of aflatoxin (AF), cyclopiazonic acid (CPA), vegetative compatibility groups (VCGs), and mating types. All aflatoxigenic isolates produced both AFB₁ and CPA. The most toxigenic one was CA28 which produced 164 μg AFB₁ per 5 ml PDA fungal culture and small sclerotia (S strain, sclertoium size less than 400 μm). The other aflatoxigenic strains produce AFB₁ ranging from 1.2 μg to 80 μg per 5 ml fungal culture. Twenty-one percent of the CA isolates produced AFB₁, 84% produced CPA and half formed sclerotia on at least one of three tested media. The 38 CA isolates formed 26 VCGs, 6 of which had two or more isolates and 20 contained single isolates. The S strain isolates belong to 4 different VCGs. Genomic profiling by a retrotransposon DNA probe revealed fingerprint patterns that were highly polymorphic. The predicted VCGs (Pred-VCGs) based on a similarity coefficient >80% matched the VCGs of multiple isolates determined by complementation. All isolates within a VCG had the same mating-type gene of either MAT1-1 or MAT1-2. Uncorrected and VCG-corrected MAT1-1 and MAT1-2 among the isolates were equally distributed.     

Feeling the pressure at home: Predator activity at the burrow entrance of an endangered arid‐zone skink

Habitat modification and invasive species are among the most important contemporary drivers of biodiversity loss. These two threatening processes are often studied independently and few studies have focused on how they interact to influence species declines. Here we assess the predation pressure placed on the threatened great desert skink (Liopholis kintorei) and how this interacts with fire‐induced habitat modifications. We collected daily track data of potential predators for 1 month at 30 great desert skink burrow‐systems where vegetation cover varied significantly after experimental burns. We used these data to evaluate potential predation pressure at the burrow‐system and assess whether fire influenced predator pressure. We supplemented this analysis by documenting predation via the inspection of large mammalian predator scats collected from great desert skink habitat. The level of feral cat activity at a burrow‐system entrance was significantly higher than that of any other potential predator, however fire had no effect on the visitation rates of feral cats, dingoes or large snakes to great desert skink burrow‐systems. The remains of great desert skink were found significantly more frequently in feral cat scats, compared to fox and dingo scats. We provide the first direct evidence that feral cats are a significant predator for great desert skink, thus supporting the hypothesis that feral cat predation is a key threatening process. Feral cat activity was not influenced by small‐scale experimental burns, however, this does not preclude an effect of larger scale fires and we recommend further research exploring this possible interaction.     

Culture media and sources of nitrogen promoting the formation of stromata and ascocarps in Petromyces alliaceus (Aspergillus section Flavi)

Petromyces alliaceus Malloch and Cain is the only known sexually reproducing fungus classified in Aspergillus section Flavi. The goal of this research was to identify culture media and sources of nitrogen that best support the formation of stromata with ascocarps. Three cultures of P. alliaceus isolated from crop field soils were grown on selected agar media in Petri dishes for 7 months at 30 degrees C in darkness. The largest numbers of stromata were recorded for cultures grown on Czapek's agar (CZA) and a mixed cereal agar (MCA), while the percentage of stromata containing ascocarps was greatest (P相似文献   

Synnema and sclerotium production in Aspergillus caelatus and the influence of substrate composition on their development in selected strains

The ability of Aspergillus caelatus, a species in Aspergillus section Flavi, to produce synnemata and sclerotia was investigated. Forty-eight isolates of A. caelatus differed widely in their production of synnemata and sclerotia; 83% of the isolates produced varying numbers of synnemata and sclerotia, and 17% produced neither sclerotia nor synnemata. Most strains produced synnemata and mostly sessile and few stipitate sclerotia on the same Czapek agar (CZA) plate. Two strains of A. caelatus were selected for further study because of the contrasting morphology of their synnemata and sclerotia. Those strains are NRRL 25528, the type species and a representative of the synnema- and black sclerotium-forming isolates, and NRRL 26119, considered an atypical strain that produced numerous synnemata and few slightly melanized or tan sclerotia. The induction and maturation of sclerotia in A. caelatus were affected greatly by the type of media as well as the kind and concentration of the carbon and nitrogen sources. CZA induced synnema and sclerotium production in both strains, whereas other media did not. Production of abundant synnemata and sclerotia also occurred when the carbon source in CZA is replaced with dextrose, xylose, cellobiose, melibiose and trehalose. CZA amended with serine, threonine, KNO(3) and NaNO(3) induced the production of numerous sclerotia and synnemata. For both strains, the optimal levels of sucrose and NaNO(3) for maximum production of synnemata or sclerotia were 3 and 0.9%, respectively. The production of synnemata and stipitate/sessile sclerotia by several wild-type strains of A. caelatus further substantiates previous suggestions for an evolutionary link between Aspergillus section Flavi and synnematal species A. togoensis, which also produces stipitate sclerotia.     

Aspergillus bombycis genotypes (RFLP) from silkworm cultivation

 Eighteen isolates of Aspergillus bombycis from samples of dust, insect frass, and soil collected from eight silkworm rearing facilities in Japan, as well as single silkworm rearing facilities in Indonesia and Malaysia, were subjected to DNA fingerprinting. PstI digests of total genomic DNA from each isolate were probed using the pAF 28 repetitive sequence. Among 18 isolates analyzed, 7 distinct DNA fingerprint groups were identified, including GTAb-2 isolated from rearing facilities in four prefectures of Japan. Aspergillus bombycis isolates share several features in common with domesticated yellow-green aspergilli, the koji molds used in traditional Oriental food fermentations, including a loose and deep colony texture, smooth-walled stipes, and the absence of sclerotia. Although aflatoxin is unknown from koji molds, all isolates of A. bombycis produced B and G aflatoxins. Aflatoxin has been linked to increased virulence in Aspergillus disease of silkworms, and there should be strong selection for aflatoxin production among clonal populations of A. bombycis adapted to silkworm cultivation. A hypothesis is offered that A. bombycis isolates from silkworm cultivation represent highly adapted forms of yet to be discovered “wild” populations that may infect Bombyx mandarina. Received: December 24, 2002 / Accepted: March 10, 2003 RID="*" ID="*" Disclaimer: Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the products, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable Acknowledgments We thank Dr. Akira Nakagiri, Institute for Fermentation, Osaka, for providing Aspergillus cultures isolated from diseased silkworms.     

Common genotypes (RFLP) within a diverse collection of yellow-green aspergilli used to produce traditional Oriental fermented foods

 DNA fingerprinting was performed on 72 strains of Aspergillus oryzae and 9 strains of Aspergillus sojae isolated from chu (China) or koji (Japan) mold inoculum used in the production of traditional Oriental fermented beverages or foods including soy sauce, miso, and sake. The cultures were deposited with the ARS Culture Collection (NRRL) between 1909 and 2001. PstI digests of total genomic DNA from each isolate were probed using the pAF28 repetitive sequence. All strains of A. sojae that we examined produced an identical DNA fingerprint and belong to the same DNA fingerprint group (GTAo-9). Strains of A. oryzae were distributed among 41 DNA fingerprint groups, including GTAo-12 represented by 11 strains, GTAo-19 represented by 5 strains, GTAo-5 and GTAo-15 each represented by 4 strains, and GTAo-8, GTAo-17, and GTAo-24 each represented by 3 strains. Thirty-three single strain isolates of A. oryzae produced unique fingerprints. Our data offer evidence suggesting that (1) the successful domestication of A. parasiticus genotypes yielding A. sojae occurred far less frequently than among genotypes of A. flavus var. oryzae; and (2) some Aspergillus genotypes employed in different fermentations and regions were derived from a common ancestral clonal population. Received: February 18, 2002 / Accepted: April 22, 2002     

Diversity of <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> genotypes (RFLP) isolated from traditional soy sauce production within Malaysia and Southeast Asia

DNA fingerprinting was performed on 64 strains of Aspergillus oryzae and 1 strain of Aspergillus sojae isolated from soy sauce factories within Malaysia and Southeast Asia that use traditional methods in producing “tamari-type” Cantonese soy sauce. PstI digests of total genomic DNA from each isolate were probed using the pAF28 repetitive sequence. Strains of A. oryzae were distributed among 32 genotypes (30 DNA fingerprint groups). Ten genotypes were recorded among 17 A. oryzae isolates from a single soy sauce factory. Genotypes Ao-46 and GTAo-47, represented by 8 and 5 strains, respectively, were isolated from a soy sauce factory in Kuala Lumpur and factories in two Malaysian states. Four strains of GTAo-49, isolated from three soy sauce factories in Malaysia; each produced sclerotia. Two strains were found to be naturally occurring color mutants of NRRL 32623 (GTAo-49) and NRRL 32668 (GTAo-52). Only two fingerprint matches were produced with the 43 DNA fingerprint groups in our database, representing A. oryzae genotypes from Japan, China, and Taiwan. Aspergillus sojae NRRL 32650 produced a fingerprint matching GTAo-9, the only known genotype representing koji strains of A. sojae. No aflatoxin was detected in broth cultures of these koji strains as determined by TLC.     

DNA fingerprinting analysis of Petromyces alliaceus (Aspergillus section Flavi)

The objective of this study was to evaluate the ability of the Aspergillus flavus pAF28 DNA probe to produce DNA fingerprints for distinguishing among genotypes of Petromyces alliaceus (Aspergillus section Flavi), a fungus considered responsible for the ochratoxin A contamination that is occasionally observed in California fig orchards. P. alliaceus (14 isolates), Petromyces albertensis (one isolate), and seven species of Aspergillus section Circumdati (14 isolates) were analyzed by DNA fingerprinting using a repetitive sequence DNA probe pAF28 derived from A. flavus. The presence of hybridization bands with the DNA probe and with the P. alliaceus or P. albertensis genomic DNA indicates a close relationship between A. flavus and P. alliaceus. Twelve distinct DNA fingerprint groups or genotypes were identified among the 15 isolates of Petromyces. Conspecificity of P. alliaceus and P. albertensis is suggested based on DNA fingerprints. Species belonging to Aspergillus section Circumdati hybridized only slightly at the 7.0-kb region with the repetitive DNA probe, unlike the highly polymorphic hybridization patterns obtained from P. alliaceus and A. flavus, suggesting very little homology of the probe to Aspergillus section Circum dati genomic DNA. The pAF28 DNA probe offers a tool for typing and monitoring specific P. alliaceus clonal populations and for estimating the genotypic diversity of P. alliaceus in orchards, vineyards, or crop fields.