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The current trends to (1) investigate sugarcane leaves as a sustainable biomass feedstock for the production of biofuels and bioproducts and (2) delivery of more leaves to factories for processing with stalks, have made information on how it deteriorates on storage during dry and wet environmental conditions more important. Brown, dry (BL) and green leaves (GL) were stripped from hand-cut whole-stalks from Louisiana (LA) sugarcane variety LCP 85-384 in two consecutive years. In the first year, BL and GL were separately allowed to deteriorate in a simulated field canopy shade study. One set was watered across 14 days to simulate rain, and the other set was not watered. This 14 day period was repeated three times across the LA harvest season (October to December) to cover varying environmental conditions: 17–31 October (21 °C; 71% mean humidity), 15–29 November (22 °C; 71%), and 13–27 December (15.5 °C; 78%). In the second year, the simulated study was repeated but over a prolonged 28 day period (17 November–15 December) and fresh and deteriorated leaves were also collected from a grower's LCP 85-384 field and analyzed for comparison. Generally, the worst deterioration for both BL and GL occurred in the watered samples, and when the humidity was highest. On deterioration, more soluble impurities were extracted from GL than BL. Only prolonged deterioration of BL caused a reduction of fiber biomass, and the fiber content of GL usually increased on deterioration because of loss of moisture. The nutrient sucrose was often, but not always, preferentially utilized over glucose and fructose. Results from the grower's field were more extreme than from the simulated experiments. Leaf moisture was higher in the deteriorated than non-deteriorated field BL because its shredded state created more surface area to absorb water; this also allowed for more Leuconostoc mesenteroides bacteria to grow and form dextran and mannitol. Overall, the total microbe populations were highest on watered GL because of higher available nutrients.

article i nfo The Aspergillus niger aggregate within the A. section Nigri is a group of black-spored aspergilli of great agro- economic importance whose well defined taxonomy has been elusive. Rep-PCR has become a rapid and cost- effective method for genotyping fungi and bacteria. In the present study, we evaluated the discriminatory power of a semi-automated rep-PCR barcoding system to distinguish morphotypic species and compare the results with the data obtained from ITS and partial calmodulin regions. For this purpose, 20 morphotyped black-spored Aspergillus species were used to create the A. section Nigri library in this barcoding system that served to identify 34 field isolates. A pair-wise similarity matrix was calculated using the cone-based Pearson correlation method and the dendrogram was generated by the unweighted pair group method with arithmetic mean (UPGMA), illustrating four different clustered groups: the uniseriate cluster (I), the As- pergillus carbonarius cluster (II), and. the two A. niger aggregate clusters (named III.A and III.B). Rep-PCR showed higher resolution than the ITS and the partial calmodulin gene analytical procedures. The data of the 34 unknown field isolates, collected from different locations in the United States, indicated that only 12% of the field isolates were N95% similar to one of the genotypes included in the A. section Nigri library. However, 64% of the field isolates matched genotypes with the reference library (similarity values N90%). Based on these results, this barcoding procedure has the potential for use as a reproducible tool for identifying the black-spored aspergilli. Published by Elsevier B.V.

Aspergillus species are increasingly important human pathogens. It is not known whether toxic metabolites of many of these pathogenic species can act as virulence factors in aspergillosis. We examined isolates of aflatoxin and ochratoxin-producing species for toxin production in ex vivo conditions. Seven of the 21 aflatoxin-producing isolates screened produced aflatoxin at 35 and 37 degrees C on the general medium yeast extract sucrose agar (YES). However, none of them produced toxin at these temperatures on brain heart infusion agar (BHA), a medium that mimics human tissue, or on BHA with modified pH or sugar levels. Six of the 12 ochratoxin-producing isolates examined produced toxin at 35 degrees C on YES. All three isolates of A. alliaceus produced ochratoxin on BHA or modified BHA at 37 degrees C. One strain of A. pseudoelegans produced a minute amount of ochratoxin on modified BHA at 37 degrees C. These data indicate that aflatoxin is an unlikely virulence, factor but that ochratoxin may be a potential virulence factor in aspergillosis.

Aflatoxins are carcinogenic mycotoxins formed by a number of fungi in the genus Aspergillus. The major fungi responsible for aflatoxin formation in crop seeds in the field and in storage are Aspergillus flavus and A. parasiticus. This review emphasizes developmental, environmental, biological, and chemical factors that influence aflatoxin formation by A. flavus and A. parasiticus.

As the number of cases of aspergillosis grows, the number of species reported to cause the disease is increasing. Historically, classification and identification of aspergilli was accomplished using morphological characteristics. A number of molecular, immunological and biochemical methods are now available. For the most part, the results of the various approaches concur, yielding similar results in identifying aspergilli, so the 'best' method for identification is the method that best suits the needs of the researcher or clinician. Each identification method has advantages and disadvantages which will be discussed herein. The paper contains a listing of some of the available identification systems from those that address the whole genus to those capable of separating intraspecific strains.

Soil is presumed to be a major source of inoculum for Aspergillus flavus which contaminates cottonseed and produces the potent carcinogen, aflatoxin. Little is known about the mycoflora of the low desert soils of cotton fields where aflatoxin is a chronic problem. In this study, soils from cotton fields in southwestern Arizona and south-eastern California were assayed for filamentous fungi. Forty-two taxa, predominantly in the genera Aspergillus, Penicillium and Fusarium, were isolated. To determine whether or not compounds produced by these fungi could be potential inhibitors of A. flavus, extracts of strains of each taxon were tested for their ability to inhibit growth of A. flavus. Twelve taxa produced compounds inhibitory to A. flavus, including several strains of Fusarium solani, Penicillium vinaceum and Aspergillus auricomus.

Iturin A, a peptidolipid produced byBacillus subtilis, inhibits growth of a large number of fungi. In this study, the effects of iturin A were evaluated on nine isolates ofA. flavus and seven isolates ofA. parasiticus in liquid shake culture. The mycelial dry weight of theA. flavus isolates was not significantly influenced by iturin A, however, there was a significant reduction in mycelial dry weight for two of theA. parasiticus isolates. Aflatoxin production was significantly reduced in five of theA. flavus isolates and three of the six aflatoxigenicA. parasiticus isolates. For the other seven isolates, aflatoxin levels were either unchanged or significantly increased in the presence of iturin A. These results indicate that iturin A does not consistently reduce growth or aflatoxin production of these fungi in pure culture.

This review summarizes the health aspects of the medically important fungal genus Aspergillus. The morphology and systematics of the genus are explained as well as its biogeography. Major mycotoxins, the aspergilli that produce them, affected crops, and symptoms of the toxicoses are summarized, as are the major mycoses caused by aspergilli. The current status of the relationship between Aspergillus in the indoor environment and health issues are discussed.

Cottonseeds having fluorescent fibers were harvested from fields in Arizona and examined utilizing light microscopy and transmission electron microscopy. The occurrence of fluorescent fibers indicated that seeds had been infected by Aspergillus flavus during development. Presence of A. flavus was verified by plating portions of seeds with fluorescent fibers. Hyphae, conidial heads, and conidia were identified readily in differentially-stained cotyledon tissue processed for light microscopy. Utilization of transmission electron microscopy permitted observations on lignified seed coats and cotyledons of mature cottonseeds. Hyphae were located throughout the cotyledon and in the nonlignified layers of the seed coat. The identification of hyphae in cross sections of vessel elements within the seed coat provided ultrastructural evidence supporting the hypothesis that A. flavus may enter seeds via the vascular tissue. Controls for the microscopy studies included observations on cottonseeds with no visual signs of infection and on laboratory-grown cultures of A. flavus. These observations demonstrated that the hyphae localized within fluorescent seeds had features characteristic of A. flavus and that fungal-like structures do not occur within uninfected seeds.

Bacillus subtilis produces peptidolipid compounds of the iturin group that have been shown to have antifungal properties, but not all fungal species are sensitive to these compounds. In this study, the activity of iturin A, produced by B. subtilis strain B-3, was tested. Paper disks impregnated with various concentrations of iturin A were placed on agar plates seeded with conidia of toxigenic species of Fusarium, Gerlacia, Penicillium or Aspergillus. Most isolates were inhibited at iturin A concentrations as low as 4 micrograms/disk. Penicillium italicum, P. viridicatum, A. ochraceus and A. versicolor were most strongly inhibited by the iturin whereas P. citrinum and A. parasiticus were least sensitive to iturin A.

Twenty-seven mature cotton bolls with Aspergillus flavus Link colonies naturally occurring on the surface of the boll or lint were collected in the field in Arizona along with their subtending stems and peduncles. Bolls inoculated through the carpel wall 30 days after anthesis were allowed to mature in the field and were collected in the same manner. The seed and stem and peduncle sections of each boll were surface-sterilized, plated on agar media and observed for A. flavus. Seventy-eight percent of the naturally contaminated bolls with A. flavus in the seed also had the fungus in the stem and peduncle, whereas only 31% of the naturally contaminated bolls with no A. flavus in the seed had the fungus in the stem or peduncle. This difference was significant (P = 0.0125), indicating a positive relationship between seed infection and stem and peduncle infection. All of the bolls inoculated through the carpel wall had A. flavus in the seed, but only 11% of the stem and peduncle sections were infected, indicating that the fungus does not readily grow downward from the boll into the supporting stem or peduncle. This unidirectional pattern of movement (upward) was further substantiated in greenhouse experiments where cotton seedlings were inoculated at the cotyledonary leaf scar with A. flavus and plants were sequentially harvested, surface sterilized and plated. Aspergillus flavus was isolated from the cotyledonary leaf scar, flower buds, developing bolls, and stem sections in the upper portion of the plant. It was never isolated from roots or stem sections below the cotyledonary node, again indicating that the fungus does not readily move downward through the plant.

Cotton dust associated with high pulmonary function decrements contains relatively high levels of mannitol. In this study, cotton leaf and bract tissue and dust isolated from cotton leaf tissue were examined by optical microscopy, scanning electron microscopy, and capillary gas chromatography. Alternaria alternata, Cladosporium herbarum, Epicoccum purpurascens , and Fusarium pallidoroseum were isolated from cotton leaf dust. The fungal samples, cotton dust, and cotton leaf contained mannitol. This study demonstrates that fungi from a late-fall harvest of cotton leaf material produce mannitol and are a probable source of the mannitol found in cotton dust.

Fusarium semitectum Berkeley and Ravenel and other nonpathogenic fungi appear to contaminate immature cottonseed but cannot express themselves until immediately after seed maturation. It is hypothesized that catechin prevents fungal outgrowth and that inhibition is released when catechin is polymerized during seed maturation.

Cotton flowers in replicate plots in two fields near Phoenix, Ariz., were tagged in June at the beginning of the flowering period. Flowers or developing bolls from these tagged flowers were inoculated on the involucral (bracteal) nectaries with dry spores of Aspergillus flavus. The bolls were harvested as they matured in August, and the seeds were assessed for the presence of the fungus. The number of infected seed from flowers and bolls inoculated up to 25 days after anthesis was significantly higher than that in uninoculated controls. Seeds from bolls inoculated after 25 days postanthesis did not differ significantly from controls in degree of infection. We postulate that the sharp decline in the ability of the fungus to infect the plant and seed is a result of physical or biochemical changes in the boll as it reaches physiological maturity or biochemical changes in the entire plant as it develops.