Mushroom Sporophores Research Articles

Pathogenic variation in isolates of Pseudomonas causing the brown blotch of cultivated mushroom, Agaricus bisporus.

Twenty seven bacterial isolates were isolated from superficial brown discolorations on the caps of cultivated Agaricus bisporus. After White Line Assay (WLA) and the assist of Biolog computer-identification system, isolates were divided into groups: (I) comprised ninteen bacterial isolates that positively responded to a Pseudomonas “reactans” reference strain (NCPPB1311) in WLA and were identified as Pseudomonas tolaasii, (II) comprised two isolates which were WLA+ towards the reference strain (JCM21583) of P. tolaasii and were proposed to be P. “reactans”. The third group comprised six isolates, two of which weakly responded to the strain of P. tolaasii and were identified as P. gingeri whereas the other four were WLA-and identified as P. fluorescens (three isolates) and P. marginalis (one isolate). Isolates of P. tolaasii showed high aggressiveness compared with those of P. “reactans” in pathogenicity tests. Cubes of 1 cm3 of A. bisporus turned brown and decreased in size when were inoculated with 10 µl of P. tolaasii suspension containing 108 CFU ml-1, whereas a similar concentration of P. “reactans” caused only light browning. Fifty µl of the same concentration of P. tolaasii isolates gave typical brown blotch symptoms on fresh mushroom sporophores whereas the two P. “reactans” isolates caused superficial light discoloration only after inoculation with 100 µl of the same concentration. Mixture from both bacterial suspensions increased the brown areas formed on the pileus. This is the first pathogenicity report of P. tolasii and P. “reactans” isolated from cultivated A. bisporus in Egypt.

Proximate composition and nutrient content of some wild and cultivated mushrooms of Ghana

Some chemical analysis and sensory data of the fruitbodies of eight mushroom species- Auricularia auricula, Coprinus disseminatus (Bull. ex. fr.) Fr, Pleurotus sajor-caju (Fr.) Sing. strain SH-l, Pleurotus sajor-caju (Fr.) Sing strain SM-1, Pleurotus ostreatus (Jacq. ex. fr) Kummer strain EM-l, Pluteus subcervinus (Schaeff Ex. Fr) Kummer, Termitomyces species and Volvariella volvacea (Bull ex. fr.) were investigated. Proximate composition: moisture, protein, fat, ash, carbohydrate; major mineral constituents (Na, Ca, P, K), one minor mineral (Fe) constituent and vitamin C content were determined. The protein content ranged from 6.2 to 30.9 percent; carbohydrate, a major constituent in mushroom species was highest in Pleurotus sajor-caju (Fr.) Sing. strain SH-l (77.2 percent) whilst Auricularia auricula contained 23.5 percent. Values for fat content ranged from 1.1 to 10.8 percent. Ash content ranged between 2.9 to 24.2 percent. Mineral content (P and K) in the mushroom sporophores were found to be higher than in many fruits, and vegetables. From the sensory data Termitomyces species was the most preferred and accepted of the-mushrooms studied.

Effect of60Co-irradiation on Postharvest Quality and Selected Enzyme Activities of Hypsizygus marmoreus Fruit Bodies

Hypsizygus marmoreus fruit bodies were exposed to different doses of (60)Co gamma-irradiation, stored at 4 degrees C and 65-70% relative humidity, and various physiological changes associated with postharvest deterioration, as well as the activities of selected enzymes widely considered to play a role in the process of senescence, were monitored over a subsequent storage period of 25 days. Exposure to 0.8 kGy irradiation was clearly beneficial in maintaining the postharvest appearance of the mushroom sporophores compared to non-irradiated samples and fruit bodies exposed to higher doses (1.2-2.0 kGy) of irradiation. Samples treated with 0.8 kGy also exhibited smaller initial declines in soluble protein, smaller increases in reducing sugar content, and lower levels of malondialdehyde accumulation during the early storage period. Smallest increases in proteinase activity were recorded in samples dosed with 0.8 and 2.0 kGy, and levels of superoxide dismutase were significantly higher in samples exposed to 0.8 kGy compared with non-irradiated controls. Large initial increases in catalase activity were detected in samples irradiated with 0.8, 1.2, and 1.6 kGy and, although enzyme levels gradually decreased in all samples during further storage, residual levels after 25 days were still severalfold higher in irradiated samples compared with controls. The data increase the current understanding of the effects of gamma-irradiation on the biochemical changes associated with postharvest senescence and should lead to more targeted strategies for reducing postharvest quality loss in H. marmoreus and other mushrooms.

Effect of supplementation of rice straw with biogas residual slurry manure on the yield, protein and mineral contents of oyster mushroom

Popularity of oyster mushroom is increasing for its ease of cultivation, high yield potential as well as its high nutritional value. Laboratory experimentation followed by farm trial with a typical oyster mushroom Pleurotus sajor caju revealed that the yield potential of these mushrooms can be increased significantly when grown on a lignocellulosic crop residue—rice straw supplemented with biogas residual slurry manure in 1:1 ratio as substrate. Residual slurry manures obtained from biogas plants utilising either cattle dung, poultry litter, jute caddis or municipal solid waste as substrates for biogas production were all effective in increasing the yield of Pleurotus sajor caju significantly although to different extents. Disinfection of straw and manure by means of 0.1% KMnO 4 plus 2% formalin solution in hot water caused 42.6% increase in yield of Pleurotus sajor caju over control, i.e., when disinfection done with hot water. In addition to increased yield, the above treatments caused significant increase in protein content, reduction in carbohydrate and increase in essential mineral nutrients in mushroom sporophores. Thus, it is concluded from the study that supplementation of rice straw with biogas residual slurry manure has strong impact in improving the yield potential, protein and mineral nutrient contents of Pleurotus sajor caju mushroom in Indian subcontinent or similar climatic conditions.

Pseudomonas costantinii sp. nov., another causal agent of brown blotch disease, isolated from cultivated mushroom sporophores in Finland.

Pathogenic bacteria are frequently associated with mushroom sporophores exhibiting brown blotch disease symptoms. These bacteria belong mainly to Pseudomonas tolaasii or occasionally to 'Pseudomonas reactans'. Although a group of isolates originating from some Finnish mushroom farms satisfied the two characteristic criteria for diagnosis of infection with P. tolaasii (i.e. yielding a typical brown blotch symptom on Agaricus bisporus sporophores and producing a typical white line in agar when streaked towards the 'P. reactans' LMG 5329 inducing strain), results based on numerical taxonomy, siderotyping, DNA-DNA hybridizations and 16S rDNA phylogenetic analyses supported the view that these isolates constituted a novel species within the genus Pseudomonas, Pseudomonas costantinii. The type strain is PS 3a(T) (= CFBP 5705(T) = HAMBI 2444(T)).

Pseudomonas costantinii sp. nov., another causal agent of brown blotch disease, isolated from cultivated mushroom sporophores in Finland

Pseudomonas costantinii sp. nov., another causal agent of brown blotch disease, isolated from cultivated mushroom sporophores in Finland

Extension of mushroom (Agaricus bisporus) shelf life by gamma radiation

Fresh mushroom sporophores (Agaricus bisporus) were placed in trays and covered with PVC film. Forty-eight of the number of packs were irradiated by a γ-source with a dose of 3 kGy, and the remaining 24 treated as control packs. Both treated and control samples were subsequently stored at 10 ± 2°C and relative humidity of 94 ± 6%. After storage, mushrooms were subjected to quality assessments and taste panel-testing, both raw and when cooked. Irradiated sporophores had an extended shelf-life compared with control samples, with less browning and a delay in cap opening. Desiccation was slowed and stipe elongation reduced so that irradiated mushrooms were still acceptable for consumption 16 days after treatment. Deleterious effects of irradiation at this relatively low level were not observed.

Ageing of the mushroom (Agaricus bisporus) under post-harvest conditions

Mushroom sporophores (Agaricus bisporus) as closed caps 3–5 cm in diameter were analysed for membrane constituents and properties, and compared with similar tissue from mushrooms stored for 3 days at 20°C. The leakage of non-specific or specific (K+) ions from pileus tissue was unaffected by storage, as was the content and composition of phospholipids and fatty acids. The sterol/phospholipid ratio and the fluidity of liposomes was unaffected by ageing. However, the membrane proteins in pileus and gill tissue decreased, but membrane viscosity remained constant. In contrast to higher plants, mushroom senescence appears to be independent of degradation of specific membrane lipid components.

Biochemical changes associated with mushroom quality in Agaricus spp.

Activities of tyrosinase (polyphenol oxidase) and protease, together with levels of phenol and protein, were determined in tissues taken from mushroom sporophores to identify quality differences in three strains of Agaricus ( Agaricus bisporus, strain U3, and A. bitorquis, strains AGC W20 and ATCC 32675). In all strains the skin tissue had greater tyrosinase activity, protein levels, and phenol levels than the flesh tissue. Strain U3 exhibited the highest native tyrosinase activity, while AGC W20 had the lowest. Tyrosinase in tissue extracts of all three strains was shown to be activated in vitro by sodium dodecyl sulfate and trypsin. The activation of tyrosinase in U3, particularly by trypsin, was greater than in either A. bitorquis strain. A convergence of activated and native tyrosinase activities occurred during storage, indicating a possible in vivo action. Protease activity in skin and flesh tissues of the sporophore increased during storage, while protein levels fell. Inhibitor studies of the protease activities from senescent sporophores indicated that the major components were metallo- and serine-proteases. Phenol levels from the skin of AGC W20 were found to be consistently lower than those of U3 and ATCC 32675. The implications of these results in relation to mushroom quality at the time of harvest and during storage are discussed.

The influence of flush number, bruising and storage temperature on mushroom quality

The cultivated mushroom (Agaricus bisporus) produces crops of mushroom sporophores periodically in what are commonly referred to as flushes. the influence of flush number and the effects of bruising on the quality of mushrooms during storage were studied. Quality was assessed throughout storage by cap colour, mushroom development and weight loss. A 10 second bruising treatment was found to discolour the mushrooms equivalent to the effect of 7 days storage at 5°C or 2 days storage at 18°C. Second flush mushrooms had less discolouration and were less yellow than those from the first or third flush. For mushrooms from different flushes the only difference in susceptibility to bruising was that the tops of first flush mushrooms were more susceptible to yellow discolouration as a result of bruising treatments than those from the second and third flushes when stored at 18°C. As the flush number increased, the rate of mushroom development in harvested sporophores during storage at 18°C decreased while weight loss increased. Results of these experiments are discussed in relation to the post-harvest physiology of mushrooms.

Effects of Caenorhabditis elegans (Nematoda: Rhabditidae) on the spread of the bacterium Pseudomonas tolaasii in mushrooms (Agaricus bisporus)

SummaryThe effects of mass‐produced saprobic rhabditid nematodes, Caenorhabditis elegans on the spread of the bacterial blotch pathogen, Pseudomonas tolaasii, were studied in mushroom growth chambers. C. elegans significantly reduced the intensity of blotch on sporophores. Repeated isolations of the bacterial flora from the gut of C. elegans recovered from mushroom sporophores during cropping, revealed the presence of Pseudomonas fluorescens biovar reactans. All the isolates of P. fluorescens biovar reactans isolated from nematodes were antagonists of P. tolaasii. C. elegans produced much larger populations in monoxenic cultures with P. fluorescens biovar reactans than with P. tolaasii. It is suggested that as C. elegans selects P. fluorescens biovar reactans rather than P. tolaasii as a food substrate it probably spreads the antagonist in the mushroom crop and may contribute to the control of bacterial blotch.

The effects of pre- and post-harvest development on mushroom tyrosinase

SummaryTyrosinase activity and the content of phenols in the skin and flesh of mushroom sporophores were assayed during pre- and post-harvest development. Skin tissue has more non-latent tyrosinase activity and phenols than the flesh. Latent tyrosinase from both tissues can be activated by trypsin or sodium dodecyl sulphate (SDS). Trypsin activation of skin tryosinase is significantly greater than by SDS, while SDS activates the flesh enzyme to a significantly greater extent. The degree of activation (the proportion of non-latent to fully activated activity) increases only during post-harvest development. The phenol content of the mushroom tissues is greater in the low-quality strain D649 than in the high quality U3. The relationships between tyrosinase activity and phenol level with mushroom quality are discussed.

The Detection and Occurrence of Virus‐like Particles in Extracts of Mushroom Sporophores [Agaricus hortensis (Cooke) Pilát

The Detection and Occurrence of Virus‐like Particles in Extracts of Mushroom Sporophores [<i>Agaricus hortensis</i> (Cooke) Pilát

Some factors affecting the growth rate of sporophores of the cultivated mushroom

The growth of sporophores of mushroom ( Agaricus bisporus) was studied using the Gompertz growth curve, and the parameters of the curve were found to vary appreciably between experiments. Three factors were identified which are associated with an increase in growth rate. These are (i) the earliness of initiation of the sporophore, (ii) the removal of adjacent sporophores, and (iii) a decrease in the number of sporophores initiated. It is suggested that the growth rate of sporophores is dependent on the substrate density in the mycelium, and also that the initiation process might be less efficient than the growth process. The implications of these findings for a mathematical modelling approach to mushroom crop growth are discussed.

Toxin Production by Pseudomonas Tolaasii Paine

Evidence is presented for the production of toxin in vitro and in vivo by P. tolaasii. Nutrient broth suspensions of P. tolaasii placed on detached mushroom sporophores but separated by a dialysis membrane caused brown discoloration and slightly sunken lesions.

Bacteria Antagonistic to Pseudomonas tolaasii and their Control of Brown Blotch of the Cultivated Mushroom Agaricus bisporus

Summary: Pseudomonas tolaasii was isolated from casing peat of healthy and diseased mushroom beds, compost of diseased mushroom beds and from soils round a mushroom farm. It was not isolated from fresh peat or compost from healthy mushroom beds. Three bacteria antagonistic to Ps. tolaasii were isolated from soil and peat. These were a nonfluorescent Pseudomonas sp. (closest to Ps. multivorans) from soil; and strains of Ps. fluorescens and Enterobacter aerogenes from peat. When the antagonists and the pathogen were added in the ratio of 8 × 107: 106 cells/ml to unsterilized peat and applied to mushroom trays, infection of mushroom sporophores by the pathogen was effectively controlled. In vitro studies failed to show lysis or growth inhibition of Ps. tolaasii by the antagonists.