A Basidiomycete Fungus Responsible for Fresh Mushroom Off-Flavour in Wines: Crustomyces subabruptus, (Bourdot & Galzin) Jülich 1978

Grape rot can cause organoleptic deviations in wines, including the aroma of fresh mushrooms; one of the molecules responsible for this is 1-octen-3-one. The bunches affected by this defect are often contaminated by Botrytis cinerea; however, they may also contain a whitish mycelium that cannot be attributed to B. cinerea. This additional fungal growth is the subject of this study. Several isolations of this fungus were carried out on grape bunches from different vineyards in the French Alsace and Champagne regions using a culture medium containing an anti-Botrytis fungicide (Boscalid). The sequencing of the ITS regions showed that most isolations corresponded to Crustomyces subabruptus (Bourdot & Galzin; Jülich 1978), an endophyte basidiomycete. Contamination tests carried out on bunches and grape juice with this fungus confirmed its responsibility for the appearance of fresh mushroom defects in wines, and showed that it has the capacity to produce large quantities of 1-octen-3-one in a wet and warm environment. The results of this study suggest that this basidiomycete is responsible for fresh mushroom aromas in wines.

Strobilurins: New group of fungicides

Strobilurin is a group of natural products and their synthetic analogs have been widely used to control and prevent fungal diseases. Strobilurins were firstly isolated in 1977 from the mycelium of Strobilurus tenacellus, a saprobic Basidiomycete fungus causing wood-rotting on forest trees. This group of pesticides was designed to manage fungal pathogens classes such as Ascomycetes, Basidiomycetes, and Oomycetes. Also, Strobilurin commercialized included derivatives such as are azoxystrobin, kresoxim-methyl, picoxystrobin, fluoxastrobin, oryzastrobin, dimoxystrobin, pyraclostrobin and trifloxystrobin. This group is a part of the larger group of QoI inhibitors, which act to inhibit the respiratory chain at the level of Complex III. Strobilurins group control an unusually wide array of fungal diseases, included water molds, downy mildews, powdery mildews, leaf spotting and rusts. This group are used on cereals, field crops, fruits, tree nuts, vegetables, turfgrasses and ornamentals. Also, Strobilurins found to enhance the plant growth in some cases.

Direct Ethanol Production from Xylan and Acorn Using the Starch-Fermenting Basidiomycete Fungus Phlebia acerina

During our search for ethanol-producing basidiomycete fungi for a wide range of substrates, we isolated Phlebia acerina, which is a white rot basidiomycete fungus. It favorably converted starch into ethanol with approximately 70% yield. Although the yield decreased as the starch concentration increased, growth and fermentation were observed even at 200 g/L of starch. P. acerina produced ethanol from glucose, galactose, mannose, xylose, cellobiose, and maltose with 93%, 91%, 86%, 72%, 92%, and 68% yields, respectively. Additionally, P. acerina, which secreted xylanase and xylosidase, was capable of assimilating xylan and directly converting it to ethanol with a yield of 63%. Furthermore, P. acerina produced ethanol directly from acorns, which are plant fruits containing starch and tannins, with a yield of 70%. Tannin delayed mycelia growth, thus prolonging ethanol production; however, this did not particularly affect the yield. These results were similar to those of fermentation in a medium with the same amounts of starch and tannin as the target crop acorn, thus suggesting that P. acerina could successfully produce environmentally friendly ethanol from starch-containing lignocellulosic biomass, unlike previously reported ethanol-producing basidiomycete fungi.

Anti-obesity effects of Grifola frondosa through the modulation of lipid metabolism via ceramide in mice fed a high-fat diet

Obesity is characterized by massive fat deposition and is related to a series of metabolic complications, such as insulin resistance (IR) and steatohepatitis. Grifola frondosa (GF) is a basidiomycete fungus...

Purification and Characterization of Two Novel Laccases from Peniophora lycii

Although, currently, more than 100 laccases have been purified from basidiomycete fungi, the majority of these laccases were obtained from fungi of the Polyporales order, and only scarce data are available about the laccases from other fungi. In this article, laccase production by the white-rot basidiomycete fungus Peniophora lycii, belonging to the Russulales order, was investigated. It was shown that, under copper induction, this fungus secreted three different laccase isozymes. Two laccase isozymes—Lac5 and LacA—were purified and their corresponding nucleotide sequences were determined. Both purified laccases were relatively thermostable with periods of half-life at 70 °C of 10 and 8 min for Lac5 and LacA, respectively. The laccases demonstrated the highest activity toward ABTS (97 U·mg−1 for Lac5 and 121 U·mg−1 for LacA at pH 4.5); Lac5 demonstrated the lowest activity toward 2,6-DMP (2.5 U·mg−1 at pH 4.5), while LacA demonstrated this towards gallic acid (1.4 U·mg−1 at pH 4.5). Both Lac5 and LacA were able to efficiently decolorize such dyes as RBBR and Bromcresol Green. Additionally, phylogenetic relationships among laccases of Peniophora spp. were reconstructed, and groups of orthologous genes were determined. Based on these groups, all currently available data about laccases of Peniophora spp. were systematized.

Sterile White Basidiomycete Fungus Marasmius graminum: A New Pathogen Causing Seedling Blight in Rice

In April 2018, damping-off of rice (Oryza sativa L.) seedlings at the 2-to-3-leaf stage was observed in three fields in the counties of Wharton and Matagorda of Texas and Jefferson-Davis Parish of Louisiana. All affected areas were 1 ha or greater, with 10 to 20% of the seedlings showing the symptoms. Infected seedlings showed dark-brown necrotic lesions on the roots and/or mesocotyls where white superficial mycelium was usually present. Symptomatic tissues excised from 10 diseased seedlings of each field were surface sterilized with 1% NaOCl, double rinsed in sterilized distilled water, and plated on potato dextrose agar (PDA). The plates were incubated at 25°C with a 12-h photoperiod in a growth chamber. After 48 h, hyphal tips of fungal colonies were transferred onto PDA and 12 isolates were obtained. Clamp connections and dolipore septa were observed in young hyphae, indicating that these isolates were a basidiomycete fungus. Young hyphal cells were binucleate based on safranin O stain (Bandoni 1979). No fruiting bodies or sclerotia produced on PDA after one month of incubation. Based on these morphological characteristics, these isolates were identified as belonging to sterile white basidiomycetes (SWB) (Howard et al. 1977). To further identify the isolates into the species level, the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of a representative isolate was sequenced with primer ITS1 and ITS4 (Vinnere et al. 2005). The ITS sequence (GenBank acc. no. MT524457) had more than 97% sequence similarity with known Marasmius graminum strains from Denmark (JN943595) (Schoch et al. 2012) and Sweden (MH857692) (Vu et al. 2019). Pathogenicity was tested with three representative isolates in a growth chamber using a modified method (Carling and Leiner 1990). Pots (6.5 cm in diameter x 7.5 cm height) were filled with 100 g of sterilized sand and watered to field capacity. Five PDA plugs (4 mm in diameter) from 5-day-old growing culture were placed on the sand surface of each pot. Pots inoculated with PDA plugs without fungus served as the controls. Five seeds of rice cv. Presidio were planted into each pot and covered with 10 g of sterilized sand. Pots were maintained at 25±2°C in a growth chamber with a 12-h photoperiod for 14 days. There were four replicated pots for each treatment and the experiment repeated twice. After 2 weeks, severe damping-off and associated symptoms similar to those observed in the field appeared in the inoculated pots. No symptoms developed in the control pots. The same fungus was consistently re-isolated from infected plants. Based on morphological characteristics and rDNA-ITS sequencing, these isolates were identified as M. graminum. The SWB fungus was first reported as a causal agent of stem rot of snap bean in Florida (Howard et al. 1977) and Nebraska (Harveson 2002), root or hypocotyl rot of corn, snap bean, squash and peanut in Georgia (Sumner et al. 1979; Bell and Sumner 1984), and crown rot of pigeon pea (Cajanus cajan) in Puerto Rico (Kaiser et al. 1987). Later, the SWB strain (ATCC 28344) causing stem rot of snap bean in Florida was further identified as M. graminum based on nuclear large subunit rRNA gene (Vinnere et al. 2005). Comparing the ITS region of this isolate (AY445120) with our isolate revealed a 99% similarity. To our knowledge, this is the first report that the SWB fungus M. graminum causes seedling blight in rice. Identification of this new disease will help to develop management strategies for control of stand loss in rice.