Highest Mycelial Growth Rate Research Articles

Multilayer perceptron-genetic algorithm as a promising tool for modeling cultivation substrate of Auricularia cornea Native to Iran.

Auricularia cornea Ehrenb (syn. A. polytricha) is a wood-decaying fungi known as black ear mushroom. Earlike gelatinous fruiting body distinguishes them from other fungi. Industrial wastes have the potential to be used as the basic substrate to produce mushrooms. Therefore, 16 substrate formulations were prepared from different ratios of beech (BS) and hornbeam sawdust (HS) supplemented with wheat (WB) and rice brans (RB). The pH and initial moisture content of substrate mixtures were adjusted to 6.5 and 70%, respectively. The comparison of in vitro growth characteristics of the fungal mycelia under the different temperatures (25, 28, and 30°C), and culture media [yeast extract agar (YEA), potato extract agar (PEA), malt extract agar (MEA), and also HS and BS extract agar media supplemented with maltose, dextrose, and fructose revealed that the highest mycelial growth rate (MGR; 7.5 mm/day) belonged to HS and BS extract agar media supplemented with three mentioned sugar at 28°C. In A. cornea spawn study, the substrate combination of BS (70%) + WB (30%) at 28°C and moisture contents of 75% displayed the highest mean MGR (9.3 mm/day) and lowest spawn run period (9.0 days). In the bag test, "BS (70%) + WB (30%)" was the best substrate displaying the shortest spawn run period (19.7 days), and the highest fresh sporophore yield (131.7 g/bag), biological efficiency (53.1%) and number of basidiocarp (9.0/bag) of A. cornea. Also, A. cornea cultivation was processed to model yield, biological efficiency (BE), spawn run period (SRP), days for pinhead formation (DPHF), days for the first harvest (DFFH), and total cultivation period (TCP) by multilayer perceptron-genetic algorithm (MLP-GA). MLP-GA (0.81-0.99) exhibited a higher predictive ability than stepwise regression (0.06-0.58). The forecasted values of the output variables were in good accordance with their observed ones corroborating the good competency of established MLP-GA models. MLP-GA modeling exhibited a powerful tool for forecasting and thus selecting the optimal substrate for maximum A. cornea production.

Morphological Characterization of Corynespora cassiicola Isolates in Culture Media

Corynespora cassiicola threatens soybean and cotton production in Brazil. The objective of this study was to evaluate cultural and morphological aspects of C. cassiicola isolated from soybean and cotton of different Brazilian regions, in culture media. The isolates were grown in PDA (Potato Dextrose Agar) and V8 juice agar media. The characteristics evaluated were: color, aspect, and growth rate of mycelia, as well as production and dimension of conidia, and number of septa per conidium. Culture media and isolates were compared using the Kruskal-Wallis or Tukey’s test at 5% significance level. The mycelia of the isolates were predominantly dark gray and light brown. C. cassiicola isolates grew better in V8 juice agar medium, presenting a higher mycelial growth rate. In PDA medium, the production of conidia was higher in isolates from cotton, compared with soybean isolates. There was great variation in the production of conidia in V8 juice agar medium, regardless of the host origin. Conidia length and width varied for isolate and culture medium. The isolates of C. cassiicola coming from cotton presented a higher number of septa per conidium when grown in PDA medium. The morphological aspects of C. cassiicola vary depending on the host of origin and the culture medium.

Production of Antioxidant Bioactive Compounds during Mycelium Growth of Schizophyllum commune on Different Cereal Media

Schizophyllum commune or split gill mushroom is a nutrient-rich natural food ingredient. Even during mycelium growth, S. commune could produce the bioactive compounds including phenolic and flavonoid compounds. The aim of this research was to characterize the production of bioactive compounds during mycelium growth period of S. commune cultured onto different eight edible cereal media (sorghum, corn, barley, wheat, oat, jasmine rice, Mun Poo rice and riceberry rice). The antioxidant activities and mycelial biomass were also observed during their growth. The results show that the highest mycelial growth rate was obtained onto barley and jasmine rice, while the lowest one was found in sorghum and corn. The concentration of phenolic compounds increased along with the mycelial growth. The fungal culture on wheat significantly exhibited the highest production of phenolic compounds which was 8.56 ± 1.09 mg GAE/g DW on day 8.The highest flavonoid production of 577.35 ± 29.93 μg CE/g DW, wasremarkably found onto barley from day 6. The degradation of certain flavonoidsin cereal materials by S. commune was also observed, particularly in riceberryrice. Antioxidant activity of cultured cereals was depended on the initial activitiesof materials and was mainly increased by S. commune metabolism. The DPPH•and ABTS•+ scavenging activities were sharply increased at day 4 which was earlystage of log phase of S. commune. At day 8, most of cereal media exhibited highDPPH• activity with a half maximal inhibitory concentration (IC50) range of 3.83-5.80 mg DW/mL, except jasmine rice. Only wheat and oat could significantly givethe highest ABTS•+ scavenging activity which was in an IC50 range of 2.38-3.27mg DW/mL. The highest FRAP activity with a median effective concentration (EC50)of 2.14 ± 0.23 mg DW/mL, was observed in barley which corresponded with itshighest flavonoid content. Antioxidant activities of S. commune culture onto cerealmedia were correspondent with their phenolic and flavonoid contents. Therefore,this study assured that several antioxidative substances were interestinglyproduced by using S. commune cultured onto the selected edible cereals, whichcould be possibly developed as a new supplement or active ingredient forpharmaceutical and food industries.

NGHIÊN CỨU ẢNH HƯỞNG CỦA CƠ CHẤT ĐẾN MỘT SỐ CHỈ TIÊU SINH TRƯỞNG, NĂNG SUẤT CỦA NẤM LINH CHI ĐỎ (Ganoderma lucidum)

The research aimed to evaluate the effects of 3 types of substrate (containing the main ingredient being Bodhi sawdust, which was treated and mixed according to 3 different formulas) on the growth and productivity of red reishi mushrooms. The results of the study showed that, of the three types of research medium formulations, Bodhi sawdust treated long-term with incubating for 168 hours was the substrate for the highest mushroom yield, reaching 96.73 g\bag, showing through the indexes of the number of fruiting body bunches\bag (3.47 bunches), fruiting body thickness (1.09 cm), fruiting body diameter (14.8 cm), polysaccharide content of mushroom (2.128%). Meanwhile, the substrate containing 70% sawdust and 30% straw substrates had the highest mycelial growth rate (1.02 cm\day) and the shortest mycelial growth time (the mushroom silk covered the whole bag at 26.3 days). Compared with the above two types of media, the formula using sawdust for short-term treatment (incubated for 48 hours) is ineffective in both the mycelial growth and fruiting body formation stages. The obtained research results contribute to perfecting the production process of red reishi mushrooms on the substrate of agricultural by-products, reducing environmental pollution and bringing economic efficiency to the farmers.

Light-Photoreceptors and Proteins Related to Monilinia laxa Photoresponses.

Light represents a ubiquitous source of information for organisms to evaluate their environment. The influence of light on colony growth and conidiation was determined for three Monilinia laxa isolates. The highest mycelial growth rate was observed under red light for the three M. laxa isolates, followed by green light, daylight or darkness. However, reduced sporulation levels were observed in darkness and red light, but conidiation enhancement was found under daylight, black and green light with more hours of exposure to light. Putative photoreceptors for blue (white-collar and cryptochromes), green (opsins), and red light (phytochromes) were identified, and the photoresponse-related regulatory family of velvet proteins. A unique ortholog for each photoreceptor was found, and their respective domain architecture was highly conserved. Transcriptional analyses of uncovered sets of genes were performed under daylight or specific color light, and both in time course illumination, finding light-dependent triggered gene expression of MlVEL2, MlPHY2, MlOPS2, and MlCRY2, and color light as a positive inductor of MlVEL3, MlVEL4, MlPHY1, and MlCRY1 expression. M. laxa has a highly conserved set of photoreceptors with other light-responsive fungi. Our phenotypic analyses and the existence of this light-sensing machinery suggest transcriptional regulatory systems dedicated to modulating the development and dispersion of this pathogen.

Biological control of sheep nematode Haemonchus contortus using edible mushrooms

This study evaluated in vitro the morphology of ten strains of edible mushroom: Pleurotus ostreatus (strains 1123 and 0152), P. eryngii (strains 1290 and 1291), P. cornucopiae (strains 1328 and 1330), Coprinus comatus (strain 1103), Panus sp. (strain 801), Lentinula edodes (strain 401) and L. boryanus (strain 402) on different growing media. In addition, the in vitro anthelmintic activity (AH) of the mycelium of the fungi against Haemonchus contortus infective larvae was evaluated in Petri dishes. Finally, organic extracts of six of the fungi were synthesized and evaluated against H. contortus larvae. The highest mycelial growth rate was achieved by P. ostreatus (0152), Panus sp. (801), and P. ostreatus (1123) in wheat flour with agar (HIT). The highest biomass (1.43 g/Petri dish) was produced by Panus sp. 801 in the HIT medium. The highest percentages of mycelial AH mortality were caused by P. ostreatus 0152, P. cornucopiae 1328, P. ostreatus 1123, P. eryngii 1292 and L. edodes 401, at 88, 88.5, 91, 93 and 93.93% respectively. The biological activity of the fungi could be due to toxins, which inhibit the movement of nematodes and subsequently degrade them. The extracts that caused the highest mortality rates were: P. ostreatus 0152 (81.6%) and P. eryngii 1292 (90.8%) at 72 h following exposure to 200 mg/mL of extract. The results of the present study show that these fungi are candidates for future in vivo tests against H. contortus.

Formation of sclerotia in Sclerotinia ginseng and composition of the sclerotial exudate.

BackgroundSclerotinia ginseng is a major devastating soil-borne pathogen of ginseng that can cause irreparable damage and large economic losses. This pathogen produces sclerotia, which are among the most persistent resting structures produced by filamentous fungi. The production of an exudate is a common feature of sclerotial development.MethodsS. ginseng was cultured on 10 different media and the following parameters were measured: mycelial growth rate (mm/day), initial formation time of exudate droplets, total quantity of exudate, number of sclerotia per dish, and sclerotial fresh/dry weight. The composition of the sclerotial exudate was analyzed using four methods (high performance liquid chromatography, gas chromatography-mass spectrometry, flame atomic absorption spectrometry, and Nessler’s reagent spectrophotometry).ResultsWe found that PDA was the optimal medium for exudate production, while SDA medium resulted in the highest mycelial growth rate. The earliest emergence of exudate droplets from sclerotia was on OA-YE and V8 media. The largest amount of sclerotia and the smallest sclerotia were produced on V8 medium. The maximum and minimum dry/fresh weight were obtained on MEA medium and V8 medium, respectively. The exudate contained organic acids (oxalic acid, gallic acid, ferulic acid, vanillic acid, caffeic acid, and tannic acid), carbohydrates (inositol, glucose, and trehalose), various ions (potassium, sodium, and magnesium), and ammonia.DiscussionThe functions of the identified compounds are discussed within the context of pathogenicity, sclerotial development, and antimicrobial activity. Our findings provide information about the production of sclerotia and the composition of sclerotial exudate that may be useful to develop strategies to control this disease.

INFLUENCE OF NUTRITIONAL AND CLIMATIC CONDITIONS ON MYCELIAL GROWTH OF THREE OYSTER MUSHROOM STRAINS

The mycelial growth rate of three oyster mushroom strains namely Pleurotus erengii, P. ostreatus and P. florida was examined on six different agar media (malt extract, Potato dextrose, rose bengal, corn meal, czapek’s dox and waksman’s glucose agar media) to select the most suitable one. Effect of pH was also examined at different values (5.0, 5.5, 6.0, 6.5 and 7.0) on the selected medium. Results indicated that Malt extract agar medium was the most suitable one for mycelium growth of all the tested mushroom strains, being the highest (9 cm ) for P. erengii and P. ostreatus at pH 7 and 9 cm at pH 6 -6.5 for P. florida after 6 days of incubation. The mycelia growth of the tested oyster mushroom strains was also examined at different temperatures (15, 20, 25, 30 and 35oC) and different levels of relative humidity (50, 65, 75, 85, 95 and 100 %) on malt extract agar medium. The highest mycelial growth rate was obtained at 25°C and relative humidity of 65% after 6 days of incubation for the three tested oyster mushrooms.

Yield, Nutritional Content, and Antioxidant Activity of Pleurotus ostreatus on Corncobs Supplemented with Herb Residues

Improper disposal of herb residues in China has caused severe problems to the surrounding environment and human safety. Three herb residues, i.e., compound Kushen injection residues (CKI) and part one and part two of Qizhitongluo Capsule residues (QC1 and QC2, respectively), were used for the cultivation of Pleurotus ostreatus. The effect of the supplementation of corncobs (CC) with different herb residues on yield, nutritional composition, and antioxidant activity of P. ostreatus was investigated. Compared to the control, the higher mycelial growth rate was observed on substrates CC +30% CKI and CC +30% QC1, while the higher yield was obtained from substrates CC +30% QC2 and CC +30% CKI. Moreover, chemical analysis of fruit bodies revealed that the addition of herb residues to CC significantly increased proteins, amino acids, ashes, minerals (Na and Ca), and total phenolic contents but significantly reduced carbohydrates and IC50 values of DPPH radicals. In addition, no heavy metals (Pb, Cd, and As) were detected in the fruiting bodies harvested from different substrate combinations. These results demonstrated that mixtures of CC with herb residues might be utilized as a novel, practical, and easily available substrate for the cultivation of P. ostreatus, which is beneficial for the effective management of herb residues.

Viral Effects of a dsRNA Mycovirus (PoV-ASI2792) on the Vegetative Growth of the Edible Mushroom Pleurotus ostreatus

A double-stranded RNA (dsRNA) mycovirus was detected in malformed fruiting bodies of Pleurotus ostreatus strain ASI2792, one of bottle cultivated commercial strains of the edible oyster mushroom. The partial RNA-dependent RNA polymerase (RdRp) gene of the P. ostreatus ASI2792 mycovirus (PoV-ASI2792) was cloned, and a cDNA sequences alignment revealed that the sequence was identical to the RdRp gene of a known PoSV found in the P. ostreatus strain. To investigate the symptoms of PoV-ASI2792 infection by comparing the isogenic virus-free P. ostreatus strains with a virus-infected strain, isogenic virus-cured P. ostreatus strains were obtained by the mycelial fragmentation method for virus curing. The absence of virus was verified with gel electrophoresis after dsRNA-specific virus purification and Northern blot analysis using a partial RdRp cDNA of PoV-ASI2792. The growth rate and mycelial dry weight of virus-infected P. ostreatus strain with PoV-ASI2792 mycovirus were compared to those of three virus-free isogenic strains on 10 different media. The virus-cured strains showed distinctly higher mycelial growth rates and dry weights on all kinds of experimental culture media, with at least a 2.2-fold higher mycelial growth rate on mushroom complete media (MCM) and Hamada media, and a 2.7-fold higher mycelial dry weight on MCM and yeast-malt-glucose agar media than those of the virus-infected strain. These results suggest that the infection of PoV mycovirus has a deleterious effect on the vegetative growth of P. ostreatus.

Optimizing bio-physical conditions and pre-treatment options for breaking lignin barrier of maize stover feed using white rot fungi.

The greatest limitation to utilization of maize stover by ruminants as a feed is the high concentration of lignin, which limits fibre digestibility. However, ruminants can effectively utilize maize stover if its nutritive value is improved using white rot fungal species. This study was designed to determine optimal bio-physical conditions for mycelial growth and select the most ideal fungal species and pre-treatment options for improving nutritive value of maize stover. Four popular edible Pleurotus fungal species (viz. Pleurotus florida, Pleurotus ostreatus, Pleurotus sajor caju and Pleurotus pulmonarius) were subjected to varying temperatures, pH levels, hydrogen peroxide (H2O2) concentration and illumination to establish the extent of mycelial growth rate. Inclusion of H2O2 was used to determine optimal levels for preservation and prevention of contamination from other indigenous microbiota. Effects of pre-treatment options on chemical composition and nutritive value of maize stover were also examined. Mycelial growth rate of Pleurotus species on potato dextrose agar (PDA) varied (P < 0.05) with temperature, pH level and H2O2 concentration following a quadratic trend. Optimal temperature, pH and H2O2 concentration for mycelial growth on PDA were 25 °C, 5 and 0.01 mL/L, respectively. Under the different bio-physical conditions, P. sajor caju had the highest mycelia density and growth rate. Chemical composition of solid-state fermented maize stover differed (P < 0.05) among the Pleurotus species. Maize stover fermented with P. sajor caju had the highest crude protein (CP) of 86.6 g/kg DM, in-vitro dry matter digestibility (IVDMD) of 731 g/kg DM, in-vitro organic matter digestibility (IVOMD) of 670.4 g/kg DM and metabolizable energy (ME) of 10.0 MJ/kg DM but with the lowest lignin (sa) of 50 g/kg DM. At 25 °C, P. sajor caju had the highest mycelial growth rate on PDA and highest lignin (sa) breakdown in the maize stover substrate. It was, therefore, selected as the most ideal fungal species for improving nutritive value of maize stover. Pre-treatment of maize stover with Lactobacillus plantarum and molasses under anaerobic condition for 7 days before inoculation with P. sajor caju resulted into a substrate with the highest (P < 0.05) CP (96.6 g/kg DM), IVDMD (752.3 g/kg DM), IVOMD (687.2 g/kg DM) and ME (10.2 MJ/kg DM). However, neutral detergent fiber exclusive of residual ash (NDFom) and lignin (sa) fractions decreased (P < 0.05) as a result of subjecting maize stover to pre-treatment with L. plantarum and molasses prior to fermentation with P. sajor caju. Therefore, pre-treatment of maize stover with L. plantarum and molasses for 7 days prior to fermentation with P. sajor caju for 14 days in darkness at 25 °C offered the greatest potential for breaking the lignin barrier.

Production of natural melanin by Auricularia auricula and study on its molecular structure

In this study, the production and structure of melanin produced by Auricularia auricula have been determined and analyzed in detail. The results showed that the highest mycelial growth rate was observed in low-carbon and carbon-free medium. In low-nitrogen and nitrogen-free medium, melanin yield was very low. Deficiency of tyrosine in medium led to weak secretion of melanin. The inorganic salt could markedly influence mycelia morphology, but did not obviously impact mycelia growth rate and melanin yield. Meanwhile the condensed molecular formula ([C18(OR)3H7O4N2]n) and structural formula of melanin were concluded based on UV–Vis, HPLC, FTIR, NMR and elemental assay. This is an eumelanin and also a macromolecular polymer of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid. The 6 main components were phenolic hydroxyl, carboxyl, amidogen, carbonyl, methylene, methyne and sulfur. This work testified that nutritional control was very important to promote melanin production, making melanin more affordable as material in food, cosmetics and medicines.

English

We examined the incidence of fusariosis in Montes Claros–MG and determined the effect of temperature and photoperiod on the development of Fusarium guttiforme. Four family production units were investigated, from which four isolates of F. guttiforme were isolated. For each isolate, two experiments were set up to assess mycelial growth for 144 h in environments with different temperatures and either a 12 h photoperiod or continuous darkness. To evaluate the development of isolates of F. guttiforme, we used a portion sub-divided randomized block design. The number of conidia produced by each isolate was counted according to the above-mentioned conditions. All production units had occurrence rates ranging from 12.2 to 64.4%. The fungal isolates showed a higher mycelial growth rate when incubated at 25°C under a 12 h photoperiod. However, the production of conidia varied depending on the temperature and on the isolate. With these overall results better understand how the spread of this fungus occurred so quickly. We may use this information to suggest management practices that reduce the incidence of pineapple fusariosis. Key words: Light, mycelial growth rate, Fusarium guttiforme, temperature.

Nitrogen fertilisation and substrate pH effects on corky root disease (Pyrenochaeta lycopersici) in greenhouse tomatoes

Corky root disease is becoming increasingly important in organic tomato production. The effects of ammonium-dominated, nitrate-dominated or balanced nitrogen fertiliser on corky root were studied in greenhouse tomatoes. The lowest disease index occurred in tomatoes with the ammonium-dominated fertiliser and the highest with the balanced nitrogen fertiliser. Disease incidence increased with increasing nitrogen level and disease severity with increasing pH value of the soil-substrate. In complementary in vitro studies, the highest mycelial growth rate of Pyrenochaeta lycopersici was observed on balanced nitrogen medium (50% nitrate: 50% ammonium) and the lowest in the nitrate-dominated medium. Regarding pH, the highest mycelial growth occurred at the optimum pH for tomato growth (pH range 5.0–6.5). No practical advice concerning fertiliser composition was possible because no treatment achieved satisfactory control of corky root. However, N fertilisation of organic greenhouse tomatoes should be based on calculated nutrient uptake by the crop.

The effect of six substrates on the growth and yield of American oyster mushrooms based on juncao technology

Mushroom cultivation in Sri Lanka is a popular cottage industry having oyster mushrooms as the most preferred variety. An investigation was carried out to study the suitability of five different plant substrates (dried banana leaves, coconut leaves, kakilla leaves (Dicranopteris dicnotonoma), paddy straw and sugar cane bagasses) for oyster mushroom cultivation in comparison with standard saw dust media as the control. Best substrate for oyster mushroom cultivation was adjudged by comparing the mycelial growth rate and the fruiting body yield values in different substrates. Although the highest mycelial growth rate was recorded in banana leaf substrate followed by paddy straw and bagasses mixtures, higher mushroom yields were recorded only in mixtures with paddy straw and bagasses which showed no significant difference to the control. Therefore it could be concluded that paddy straw and sugar cane bagasses are equally good substrates as the traditionally used saw dust media for oyster mushroom cultivation in Sri Lanka.

The β-1,3-Exoglucanase GeneexgA(exg1) ofAspergillus oryzaeIs Required to Catabolize Extracellular Glucan, and Is Induced in Growth on a Solid Surface

The biological role of ExgA (Exg1), a secretory beta-1,3-exoglucanase of Aspergillus oryzae, and the expression pattern of the exgA (exg1) gene were analyzed. The exgA disruptant and the exgA-overexpressing mutant were constructed, and phenotypes of both mutants were compared. Higher mycelial growth rate and conidiation efficiency were observed for the exgA-overexpressing mutant than for the exgA disruptant when beta-1,3-glucan was supplied as sole carbon source. On the other hand, no difference in phenotype was observed between them in the presence or absence of the inhibitors of cell wall beta-glucan remodeling when grown with glucose. exgA Expression was induced in growth on solid surfaces such as filter membrane and onion inner skin. A combination of poor nutrition and mycelial attachment to a hydrophobic solid surface appears to be an inducing factor for exgA expression. These data suggest that ExgA plays a role in beta-glucan utilization, but is not much involved in cell wall beta-glucan remodeling.

Cultivation of Culinary-Medicinal Lion's Mane Mushroom Hericium erinaceus (Bull.: Fr.) Pers. (Aphyllophoromycetideae) on Substrate Containing Sunflower Seed Hulls

The mycelial growth rates in linear growth assays, yield, and mushroom productivity of Hericium erinaceus were evaluated in a substrate containing sunflower seed hulls as the main energy and nutritional component, with the addition of different levels of Mn(II) and/or NH4+. The mycelial growth rate in substrates possessing different sunflower seed hull sizes with or without the addition of wheat bran showed that, irrespective of the presence of wheat bran, higher mycelial growth rate was observed with the larger sunflower seed hull size (as disposed of by the regional oil-seed factory without additional process). Adding growth-limiting mineral nutrients such as Mn(II) (20 or 100 ppm) and/or NH4+ (200 or 500 ppm) increased the mycelial growth rate by 8%−16%. The first flush occurred at day 10 and the second at day 30, with a production cycle duration of 55 days starting from inoculation. No statistical differences were detected between accumulated biological efficiencies coming from different substrate formulations with the addition of wheat bran, barley straw, or poplar sawdust compared to the sunflower seed hull control, but a tendency for higher yield was observed for the substrate supplemented with 20 ppm Mn and 200 ppm NH4+. Sunflower seed hulls without supplementation constitute a very good basal substrate, so this substrate by itself constitutes a very good source of energy and nutrition for H. erinaceus growth and development.

The α-tubulin gene AmTuba1: a marker for rapid mycelial growth in the ectomycorrhizal basidiomycete Amanita muscaria

The apical extension of hyphae is of central importance for extensive spread of fungal mycelium in forest soils and for effective ectomycorrhiza development. Since the tubulin cytoskeleton is known to be important for fungal tip growth, we have investigated the expression of an alpha-tubulin gene from the ectomycorrhizal basidiomycete Amanita muscaria (AmTuba1). The phylogenetic analysis of protein sequences revealed the existence of two subgroups of alpha-tubulins in homobasidiomycetes, clearly distinguishable by defined amino acids. AmTuba1 belongs to subgroup1. The AmTuba1 transcript level is related to mycelial growth rate. Growth induction of carbohydrate starved (non-growing) hyphae resulted in an enhanced AmTuba1 expression as soon as hyphal growth started, reaching a maximum at highest mycelial growth rate. Bacterium-induced hyphal elongation also leads to increased AmTuba1 transcript levels. In mature A. muscaria/P. abies ectomycorrhizas, where fungal hyphae are highly branched, and slowly growing, AmTuba1 expression were even lower than in carbohydrate-starved mycelium, indicating a further down-regulation of gene expression in symbiosis. In conclusion, our analyses show that the AmTuba1 gene can be used as a marker for active apical extension in fly agaric, and that alpha-tubulin proteins are promising tools for the classification of fungi.

Improvement of exopolysaccharide production by macro-fungus Auricularia auricula in submerged culture

The effect of culture conditions and pH on the performance of exopolysaccharide (EPS) production by Auricularia auricula, an edible and medical macro-fungus, was investigated in submerged culture. First, the optimal cultivation condition was determined in shake flasks by the single-factor tests. Second, the effect of pH on EPS production was investigated in batch submerged fermentation, a highest EPS concentration (7.5 ± 0.14 g/l), a highest mycelial growth rate but a lowest residual glucose concentration (3.9 ± 0.04 g/l) were achieved at the pH 5.5, 5.0 and 4.5, respectively. Based on kinetic parameters analysis, a two-stage pH-control strategy was proposed, in which pH was controlled at 5.0 in the first 48 h and then switched to 5.5. The effectiveness of the strategy was verified successfully by experiments. Higher concentration (8.7 ± 0.08 g/l) and productivity (0.091 g/l/h) of EPS were achieved by applying this strategy. The productivity increased 93.3, 110.4 and 45%, respectively, compared with that of the non-pH control, and controlling pH at 5.0 and 5.5. Those results demonstrated that EPS production by A. auricula was sensitive to the pH change in submerged culture. In addition, the idea of changing environmental conditions at different culture stages to suit the metabolic characteristics of cell, could be applied to the other bioactive metabolites production from macro-fungi in submerged culture.

Genetic and physiological variation in isolates of Verticillium fungicola causing dry bubble disease of the cultivated button mushroom, Agaricus bisporus

The objectives of this study were to examine genetic variation, physiological dissimilarities and diversity in pathogenicity between Verticillium fungicola var. aleophilum and var. fungicola and within a population of six V. fungicola var. fungicola strains responsible for dry bubble outbreaks on mushroom farms. Genetic variability was investigated using random amplification of polymorphic DNA (RAPD). Mycelial growth rate, extracellular enzyme production and susceptibility to hydrogen peroxide were used to examine physiological dissimilarities. Variation in pathogenicity was studied both in vitro and during mushroom cultivation. All the physiological properties studied indicated that var. aleophilum isolates were potentially more efficient than var. fungicola isolates for rapid colonisation of the mushroom cultivation medium. They could then interact more efficiently with Agaricus bisporus to produce dry bubble disease. RAPD analysis confirmed that all the French isolates belonged to var. fungicola, and two isolates were distinguishable from the homogeneous group constituted by the others. These isolates had a higher mycelial growth rate and lower extracellular enzyme activities in liquid media, except for chitinases. Their spores were more susceptible to germination inhibition by hydrogen peroxide, and they were responsible for higher levels of affected mushrooms. The two varieties might be regarded as pathotypes that are geographically isolated, and variation in isolates of var. fungicola might have consequence for mushroom growers.