SEARCH

SEARCH BY CITATION

Keywords:

  • casing;
  • dry matter;
  • mushroom size;
  • substrate;
  • temperature

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

BACKGROUND

The almond mushroom Agaricus subrufescens (formerly Agaricus blazei or Agaricus brasiliensis) is cultivated at commercial level in Brazil and some Asian countries on local substrates and casing mixtures. Despite its tropical origin, A. subrufescens might be a seasonal option for mushroom growers in western countries, where some wild strains have been isolated. For this purpose, cultivation conditions were developed starting from the substrate and casing mixture commonly used for commercial production of the button mushroom Agaricus bisporus in France.

RESULTS

The commercial compost, based on wheat straw and horse manure, used for A. bisporus and the casing mixture (peat and limestone) supplemented with fine sand proved efficient to grow A. subrufescens. Increasing the depth of the casing layer improved significantly the yield and time to fruiting. Daily variations in temperature did not markedly modify the yield. Significantly higher mushroom biomass was obtained with three wild European strains compared with three Brazilian cultivars. The very productive wild strain CA438-A gave mushrooms of size and dry matter content comparable to those of a cultivar.

CONCLUSION

Commercial production of A. subrufescens can be developed in western countries on the wheat straw-based substrate commonly used for A. bisporus in these regions, by a simple modification of the casing mixture and maintaining the incubation temperature throughout the crop, which is expected to save energy during summer. Good yields were obtained cultivating European strains under optimised parameters. © 2013 Society of Chemical Industry


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

Important cultivated edible and medicinal mushrooms belong to the Agaricus genus. Among them is the almond mushroom formerly known as Agaricus blazei Murrill. In the 2000s, two new species names, Agaricus subrufescens Peck[1] and Agaricus brasiliensis Wasser et al.,[2] were proposed for this fungus, which is believed to originate from Brazil.[3] Currently, many publications refer to the Brazilian cultivars as A. blazei or A. brasiliensis. Recently, A. subrufescens Peck was declared the correct name,[4] but the authors excluded neither the existence of infraspecific taxa nor the fact that A. subrufescens might be a complex of species. The mushroom has been produced on a commercial scale in Brazil since the early 1990s[5] and exported to several countries. Nowadays it is also cultivated at the industrial level in Japan, China, Taiwan and Korea.[6] These cultures rely on local agroindustrial waste-based substrates. The majority of articles on A. subrufescens cultivation available in the literature refer to experiments in Brazil. The raw materials commonly used to prepare the substrate are sugar cane bagasse, various grasses (e.g. Brachiaria spp., Cynodon dactylon, Panicum maximum), cereal straw (Triticum aestivum, Avena sativa, Oryza sativa) and manure supplemented with nitrogen sources (soybean, wheat, corn and cotton meal, urea, ammonium sulfate) and sources of phosphorus and calcium.[7] Experiments performed in China showed the possible use of cottonseed hulls, rice hulls, asparagus straw and soybean cake.[8, 9] Efficient A. subrufescens production was also obtained with substrate compositions closer to that used to grow the button mushroom Agaricus bisporus in temperate countries, such as cattle bedding compost/sawdust/cereal bran[10] and chicken manure/wheat straw.[6] Local soils, with or without the addition of vegetal charcoal, have been tested as an alternative to peat in the casing layer used for A. subrufescens cultivation.[11-14] The casing soil composition is important, regardless of the substrate formulation.[13] The physical characteristics of the soil contribute greatly to the mushroom yield.[12] These cultivation conditions are well adapted to tropical countries, although yields are significantly lower than those obtained with A. bisporus, but A. subrufescens might be a seasonal option for mushroom growers in western countries. They can save energy by producing the almond mushroom efficiently during summer, owing to its higher optimal temperature requirements when compared with A. bisporus. Our aim was to define cultivation conditions suitable for A. subrufescens starting from the substrate and casing mixture used for A. bisporus commercial production and making changes easy to perform by producers of button mushroom in western countries.

MATERIAL AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

Agaricus subrufescens

Three strains, CA561, CA565 and CA570, were cultivars from Brazil kept in the Collection of Germplasms of Agaricus in Bordeaux (CGAB), INRA (Bordeaux, France) since 2007; CA454 was a subculture of the strain A. blazei ATCC 76739 kept in the CGAB since 2006; CA438-A, CA487 and CA643 were wild European strains; the hybrid was obtained between CA454 and a French wild isolate (Table 1). Previous experiments have shown that the hybrid is fertile. Spawn was prepared as follows. Mycelium grown on malt agar medium was transferred to sterilized rye grain purchased from a spawn maker (Euromycel, Ile-Bouchard, France) and incubated at 23 ± 2 °C until completely colonized. The spawn was stored at 11 °C and placed at room temperature the day before spawning. Spawn storage never exceeded 2 weeks.

Table 1. Cultivars and wild strains with reference to origin and code in collection
TypeOriginCode CGABaCode FCA/UNESPb
  1. a

    Collection of Germplasms of Agaricus in Bordeaux, INRA.

  2. b

    Collection of the Mushroom Research Centre of the College of Agronomic Sciences, Sao Paulo State University, Brazil.

European wild isolatesSpainCA438-A 
Saint-Léon, Gironde, FranceCA487 
Le Pian Médoc, Gironde, FranceCA643 
Original cultivated strainCollection, subculture of ATCC 76739CA454 
Brazilian cultivarsPiedade, SP, BrazilCA561ABL-99/30
Boituva, SP, BrazilCA565ABL-03/48
Rio de Janeiro, RJ, BrazilCA570ABL-01/29
HybridObtained at INRACA454-3 × CA487-100 

Cultivation substrate

The substrate was compost prepared for commercial production of A. bisporus and provided by Renault SA (Pons, France). The main ingredients for composting were wheat straw and horse manure. Composting was performed indoors. The characteristics and mean composition of the compost were as follows: 66.8% humidity; pH 7; minerals 303.3 g kg−1, with K = 32.1, Mg = 6.4, Ca = 55.8, Na = 2.8, S = 35.8, organic C = 348 and N (Kjeldahl) = 23.1 g kg−1 (C/N = 15.1). The water-soluble organic matter (OM) and the OM insoluble in acid detergent represented 32.5 and 48.8% of total OM respectively. Hemicelluloses, celluloses and lignin + humic compounds accounted for 18.7, 2.9 and 45.9% of total OM respectively. The analyses were performed by LCA (La Rochelle, France) using normalized methods.

Standard conditions for fructification

Based on previous results,[15] trays filled with 8 kg of compost were inoculated with 1% spawn and incubated for 15 days in a climatic chamber at 23 ± 0.5 °C with 98 ± 2% relative humidity. Then 2.5 cm of casing layer C1 (casing used for commercial production of A. bisporus + fine sand, corresponding to 45% peat/20% limestone/35% fine sand (v/v/v)) was added and the trays were left under the same environmental conditions for a 7 day post-incubation period. After that the climatic chamber was set at 23 ± 0.5 °C with 97 ± 2% humidity and 1400 ± 100 ppm CO2 concentration. Time to fruiting was the number of days between casing and the first picking. The numbers and fresh weight of fruiting bodies were recorded until 65 days after casing. The experiments were performed according to a completely randomised design with four replicates per strain and cultivation condition.

Variations in casing parameters

Casing quantity

Two depths of casing layer, 2.5 cm (quantity used for A. bisporus) and 5 cm, were compared in two independent experiments, each performed with a different batch of compost.

Casing composition

Fruiting was compared using the following casing mixtures: C1 as described for standard cultivation conditions; C2 = 15% peat/23% limestone/37% fine sand/25% vegetal charcoal (v/v/v/v); C3 = 15% peat/23% limestone/42% fine sand/20% spent compost (v/v/v/v); C4 = 80% peat/20% spent compost (v/v) + CaCO3 (100 g L−1 casing mixture); C5 = 25% peat/25% limestone/50% fine sand (v/v/v). Spent compost was obtained from previous experiments performed with compost provided by Renault SA, as for the present experiments: after the last harvest of A. subrufescens mushrooms (65 days after casing), the casing layer was removed and the spent compost was collected, submitted to thermal treatment (70 °C, 12h) and matured for 2 months[16] before being used. No casing inoculum was used, whatever the casing mixture. Owing to the capacity of the climatic chamber, four to six strains were used to compare the casing mixtures (see ‘Results’). All strains were compared under the best casing conditions in two independent experiments.

Variations in temperature

The eight strains were inoculated and incubated following the standard conditions. After incubation, the trays were removed from the climatic chamber for addition of the best casing mixture. The trays were returned to the climatic chamber with the same setting for 2 days. Then the temperature was increased to 30 °C and the following temperature cycle, set automatically (Fancom BV system, Panningen, The Netherlands), was begun: decrease in temperature over 10 h 40 min at a rate of 1.4 °C h−1 and holding at this temperature for 1 h 20 min; increase in temperature over 10 h 40 min at a rate of 1.4 °C h−1 and holding at this temperature for 1 h 20 min. Standard conditions were applied for relative humidity and CO2 concentration. The air temperature in the climatic chamber was recorded. The temperature was also measured inside the compost of four trays, each inoculated with a different strain, namely CA565, CA454, CA487 and CA643. Measures were recorded automatically every 30 min with F-central for Windows Version B4.4 (Fancom BV).

Parameters of yield components of A. subrufescens

Strains were compared for time to fruiting (number of days between casing and the first picking day) and total fresh weight of fruiting bodies at the end of the experiment. Because the strains showed great variation in time to fruiting, they were also compared for biomass production during three periods extending from d1 to d10, from d1 to d20 and from d1 to d30, where d1 is the day of the first picking for the strain and d10, d20 and d30 are the 10th, 20th and 30th days following the first picking respectively. Because flushes were not always well differentiated, biomasses obtained during d1–d10, d11–d20 and d21–d30 were compared to give an idea of the kinetics of production of each strain. Mean fresh weight and dry matter content were estimated for sporophores obtained with variations in temperature. The size of fruiting bodies was measured as g per mushroom.[10]

Statistical analysis and graphical representation

Analyses of variance (ANOVA) were performed followed by Duncan's test to identify statistical differences. Box plot representation was used to show the data distribution of mushroom fresh weight and dry matter content. Cramer–Von Mises and Kolmogorov–Smirnov nonparametric tests were performed to compare data distributions.

Results

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

Effect of casing quantity

At the end of the post-incubation period, A. subrufescens mycelium had fully colonized the casing, irrespective of the quantity used. The ANOVA showed that variation in casing depth significantly modified time to fruiting (P = 0.021) and mushroom yield (P < 0.001). The absence of interaction between strain and casing (P = 0.575, 0.107, 0.104 and 0.266 for biomass recorded at the end of the experiment and during periods d1–d10, d1–d20 and d1–d30 respectively) indicated the same classification of the casing treatments for all strains. Higher mushroom biomass was obtained with the 5 cm casing layer (Table 2). This casing depth was used in the following experiments.

Table 2. Comparison of casing depth effect on time to fruiting and mushroom biomass
Casing depth (cm)Mean time to fruiting (days)aBiomass mean value (g kg−1 substrate)a
End of exp.d1–d10d1–d20d1–d30
  1. a

    Within a column, values followed by the same letter are not different at P = 0.05 by Duncan's test.

2.532.725A57.710B22.417B39.642B51.189B
528.100B93.248A39.053A65.216A83.738A

Effect of casing composition

The ANOVA revealed a significant effect (P < 0.0001) of casing composition on time to fruiting and mushroom biomass, but the significant interaction (P < 0.0001) between strain and casing composition meant that the best composition varied with the strain. No variation in time to fruiting was observed with CA 487, while the other three strains showed the shortest time to fruiting with C1 and C2. CA 565 failed to fruit with C3 and C4. Casing mixtures C1 and C2 gave the best biomass at the end of the experiment. When considering biomass obtained 30 days after the first picking, C1 remained the most efficient (Table 3). The ANOVA showed that the percentage of sand in the casing mixture (C5 vs C1) had no significant effect (P = 0.05) on time to fruiting and biomass production. Variations related to the mushroom strains cultivated with C1 are presented in Table 4. Based on these results, further experiments were performed with casing mixture C1.

Table 3. Comparison of effect of four casing compositions on time to fruiting and mushroom biomass of four strains
ParameterStrainCasingb
C1C2C3C4
  1. a

    Within a row, values followed by the same letter are not different at P = 0.05 by Duncan's test.

  2. b

    C1, 45% peat/20% limestone/35% fine sand (v/v/v); C2, 15% peat/23% limestone/37% fine sand/25% vegetal charcoal (v/v/v/v); C3, 15% peat/23% limestone/42% fine sand/20% spent compost (v/v/v/v); C4, 80% peat/20% spent compost (v/v) + CaCO3 (100 g L−1).

  3. c

    No record: strain did not fruit on this casing mixture.

  4. d

    No record: strain began to fruit too late.

Time to fruiting (days)aCA48716A16A17A17A
CA64320C22C28B32A
CA56541A43A[BOND]c[BOND]
CA57027BC25C29B40A
Biomass, end of experiment (g kg−1 substrate)aCA487206.2A152.4AB77.8B202.5A
CA643122.9A97.3A15.9B16.6B
CA56521.8A24.1A0.0B0.0
CA57062.6A30.3AB3.5B21.8AB
Biomass, d1–d30 (g kg−1 substrate)aCA487193.6A126.4B72.6C163.7AB
CA643112.1A84.9B15.9C11.7C
CA565d
CA57062.6A29.2AB3.5B
Table 4. Comparison of six strains grown with casing mixture C1
StrainTime to fruiting (days)aBiomass (g kg−1 substrate)a
End of experimentd1–d30
  1. a

    Within a column, values followed by the same letter are not different at P = 0.05 by Duncan's test.

CA438-A23.2B262.1A227.8A
CA48716.5C244.8A196.4A
CA64322.7B236.8A193.1A
CA56133.2A75.7B73.9B
CA56532.7A12.8C12.6C
CA57024.3B75.1B64.4B

Strain comparison on substrate covered with 5 cm of casing mixture C1

The ANOVA showed a significant effect (P < 0.001) of the experiment (substrate effect), but no interaction (P = 0.05) between strain and experiment was detected, meaning that the classification of the strains for the different parameters tested was the same in the two experiments.

Important variability in time to fruiting was observed among the eight strains (15–48 days). The wild European strains and the hybrid began to fruit significantly earlier than CA454 and the cultivars (Table 5).

Table 5. Comparison of eight strains for time to fruiting and biomass production on substrate covered with 5 cm of casing mixture C1
StrainTime to fruiting (days)aBiomass (g kg−1 substrate)aBiomassb
End of exp.d1–d10d1–d20d1–d30d1–d10d11–d20d21–d30
  1. a

    Within a column, values followed by the same capital letter are not different at P = 0.05 by Duncan's test.

  2. b

    Within a row, values followed by the same lowercase letter are not different at P = 0.05 by Duncan's test.

  3. c

    No record: strain began to fruit too late.

  4. d

    As g kg−1 substrate.

  5. e

    As % biomass (d1–d30).

CA438-A18.5DE139.2AB49.0C81.5B102.6B49.0da (47.7)e32.5b (31.7)21.2c (20.6)
CA48715.1E166.2A95.3A139.5A157.5A95.3a (60.5)44.3b (28.1)18.0b (11.4)
CA64320.8CD119.8AB77.1AB88.4B109.2B77.1a (70.6)20.8b (19.0)11.4b (10.4)
CA45430.4B11.5C7.2D7.4C11.5C7.2a (63.0)4.1ab (35.5)0.1b (1.5)
CA56127.0B38.6C13.8D24.3C34.9C13.8a (39.7)10.7a (30.5)10.4a (29.8)
CA56548.8A9.4C4.5Dc4.5a (100)
CA57026.8B24.1C14.2D18.2C20.5C14.2a (69.5)4.0b (19.3)2.3b (11.2)
Hybrid22.8C117.4B58.6BC91.3B99.4B58.6a (59.0)32.6b (32.8)8.1c (8.2)

Mushroom biomass produced at the end of the experiment or during the same period of time since the first picking (d1–d10, d1–d20 or d1–d30) clearly separated the wild European strains and the hybrid from the Brazilian strains and showed that the latter were significantly less productive (Table 5). Mushroom biomass obtained during the three successive periods of 10 days after the first picking showed that the productivity of the strains decreased significantly after the first period, except for CA561. For all strains but CA438-A and CA561, mushrooms harvested during the first period (d1–d10) represented more than 50% of the biomass collected during the d1–d30 period (Table 5). Mushroom biomass was significantly and negatively correlated with time to fruiting (r = 0.751, P = 0.032 for d1–d10; r = 0.948, P = 0.001 for d1–d20; r = 0.963, P < 0.001 for d1–d30).

Effect of variations in temperature

During incubation and the couple of days following casing, minimum, maximum and mean air temperatures ranged from 20 to 21.5 °C, from 21.2 to 23.4 °C and from 20.8 to 22.4 °C respectively (Fig. 1). Until the 10th day of incubation, composts of the four strains showed similar small variations in temperature. Thereafter the temperature kinetics varied dramatically with the strain. Small variations were observed with CA643, for which the compost temperature ranged from 23.9 to 24.1 °C during the day before casing. In compost inoculated with CA487, the temperature reached 27.7 °C on day 11 then declined gradually to 24.1 °C. In contrast, the temperature increased from 24 to 28 °C from day 12 in compost inoculated with CA454. Moderate variations ranging from 25.9 to 27.7 °C were recorded in the CA 565 compost (Fig. 2). The mycelium of all strains except CA454 and CA565 developed intensively in the compost. Homogeneous but less dense colonization was observed with CA454 and CA565 at the end of the incubation step.

image

Figure 1. Minimum, maximum and mean air temperatures measured daily in climatic room during incubation and couple of days following casing.

Download figure to PowerPoint

image

Figure 2. Temperature measured in substrate of four strains during incubation and couple of days following casing.

Download figure to PowerPoint

Rapidly after daily variations in temperature were applied, minimum, maximum and mean air temperatures ranged from 14.3 to 18.3 °C, from 25.5 to 28.4 °C and from 19.9 to 23.1 °C respectively. Despite computer control, the maximum air temperature recorded in the climatic room showed a peak centred on the d42–d53 period (Fig. 3) because of a dramatic increase in the outdoor temperature, which reached 31.6 °C on d50. Similar daily fluctuations in compost temperature occurred for the four strains until the end of the experiment. Minimum temperatures varied from 17.5 to 19.4 °C and maximum temperatures from 23.7 to 26.8 °C (Fig. 4). Around d50, the temperature measured in the compost showed a peak that followed the variations in air temperature. The small volume of compost per tray (0.018 m3) could explain such variations. No explanation can be proposed for the peaks of temperature recorded around d24 and d35 in the compost of CA454.

image

Figure 3. Minimum, maximum and mean air temperatures measured daily in climatic room from day 3 after casing to end of experiment.

Download figure to PowerPoint

image

Figure 4. Minimum, maximum and mean temperatures recorded daily in substrate of four strains from day 3 after casing to end of experiment.

Download figure to PowerPoint

The wild European strains and the hybrid began to fruit significantly earlier than CA454 and the cultivars (Table 6). Except for CA 565, no marked difference in time to fruiting was detected compared with cultivation under constant air temperature presented in Table 5, which was confirmed by the Pearson correlation of 0.777 (P = 0.023). As regards mushroom biomass production, the Pearson correlation of 0.939 (P = 0.021) showed that variations in temperature did not markedly modify the classification of the strains. Significantly higher mushroom biomass was obtained with the three European strains compared with the Brazilian strains and the hybrid either at the end of the experiment or for periods of 10, 20 or 30 days since the first picking. Biomass produced during the d1–d10 period represented 47–63% of that recorded during the d1–d30 period for all but the two poorly productive strains CA454 and CA565 (Table 6). Amounts of biomass produced during the same period of time were significantly and negatively correlated with times to fruiting (r = 0.947, P < 0.001 for d1–d10; r = 0.956, P < 0.001 for d1–d20; r = 0.959, P < 0.001 for d1–d30).

Table 6. Effect of variations in temperature on time to fruiting and biomass production of eight strains
StrainTime to fruiting (days)aBiomass (g kg−1 substrate)aBiomassb
End of exp.d1–d10d1–d20d1–d30d1–d10d11–d20d21–d30
  1. a

    Within a column, values followed by the same capital letter are not different at P = 0.05 by Duncan's test.

  2. b

    Within a row, values followed by the same lowercase letter are not different at P = 0.05 by Duncan's test.

  3. c

    No record: strain began to fruit too late.

  4. d

    As g kg−1 substrate.

  5. e

    As % biomass (d1–d30).

CA438-A21.5CD114.6C54.5B98.4C110.1C54.5da (49.5)e44.0a (39.9)11.7b (10.6)
CA48718.5D188.9A89.2A154.4A171.1A89.2a (52.1)65.2b (38.1)16.7c (9.8)
CA64321.0D149.0B83.7A130.5B145.2B83.7a (57.7)46.8b (32.2)14.7c (10.1)
CA45433.7A7.1E6.5D6.5E7.1E6.5a (91.5)0b (0)0.6b (8.5)
CA56134.7A16.3E10.3D13.9E16.3E10.3a (63.0)3.7b (22.5)2.3b (14.5)
CA56534.0A7.5E7.5Dc7.5a (—)
CA57029.3B27.9E12.7D16.1E27.1E12.7a (46.7)3.4b (12.7)11.0a (40.6)
Hybrid25.0C74.4D38.4C60.0D62.5D38.4a (61.5)21.6ab (34.6)2.5b (3.9)

Sporophore fresh weight and dry matter content

The wild strains and the cultivar CA 561 differed significantly from CA454, the two other cultivars and the hybrid in the distribution of sporophore fresh weight, which moved towards higher values in the second group of strains (Fig. 5A).

image

Figure 5. Sporophore (A) fresh weight and (B) dry matter content of eight strains.

Download figure to PowerPoint

Data distributions of fresh weight moved significantly toward low values after the d1–d10 period for the wild strains CA438-A and CA487, while values varied in the same range throughout the crop for the third wild strain, CA643. No significant differences in the distributions obtained for the first two periods were detected for CA570 and the hybrid (Fig. 6).

image

Figure 6. Variations in sporophore fresh weight during three successive time periods under variations in temperature.

Download figure to PowerPoint

Lower dry matter contents were found in the sporophores of the wild strains CA487 and CA 643 than in those of the other strains. Distributions obtained for CA454 and two cultivars (CA561 and CA570) did not differ among themselves. High dry matter contents were measured in sporophores of CA565. The hybrid showed higher dry matter content compared with its parent CA487 but did not differ significantly from its parent CA454 for this trait (Fig. 5B).

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

Works aimed at comparing the productivity of different mushroom strains have generally considered total biomass obtained during the same period of time starting at casing. The eight strains studied in the present work showed very different time to fruiting, meaning harvests lasted for very different periods of time in experiments analysed 65 days after casing. Comparing biomass production during the same period of time is a better representation of the ability of strains to mobilise nutrients to fruit. Consequently, strains were compared for mushroom biomass 10, 20 and 30 days after the first picking.

Under our cultivation conditions (straw- and horse manure-based compost for A. bisporus, incubation and fructification in a climatic chamber), using a 5 cm casing layer instead of the 2.5 cm conventionally used in experiments with A. bisporus significantly improved biomass production of the strains tested. A similar effect of casing depth was obtained in Brazil with different casing mixtures and substrate compositions. Both 5 and 8 cm of casing mixture based on Brazilian soils were better than 3 cm for cultivating ABL-97/12 in a greenhouse on substrate prepared with local Brazilian wastes.[17] Increasing casing quantity led to higher yield in strain M7700 grown in a climatic chamber on substrate made of chicken manure, wheat straw and gypsum.[6] Besides the effect observed in a greenhouse, no improvement occurred in a bamboo-covered structure.[17] The quantity of casing material proved important for biomass production of A. subrufescens, irrespective of the strain, casing and substrate materials, but its effect could be affected by the cultivation environment.

Peat use causes the loss of non-renewable resources and participates in the greenhouse effect by the liberation of CO2 through the aerobic decomposition of carbon,[18] thus generating a worldwide demand for alternatives in agriculture. In Brazil the most utilised casing for both A. bisporus and A. subrufescens is subsoil or subsoil mixtures with charcoal,[12] and several works have shown various effects of charcoal on A. subrufescens. Rhodic Hapludox/eucalyptus charcoal 4:1 (v/v) led to a better yield of strain CS1 compared with Xanthic Hapludox or Humic Haplaquox soil.[13] In contrast, casing made of peat or shale increased the productivity of ABL-99/26 and ABL-99/29 by 10–20% compared with a mixture of 70% ravine soil/30% charcoal (v/v),[19] and lime schist or peat led to better biological efficiency of the same strains compared with a mixture of subsol/charcoal 7:3 (v/v).[12] In outdoor cultivation, strain BZ-04 showed better yield on a substrate covered with local soil horizon A compared with casing mixtures composed of 30% eucalyptus charcoal/70% local soil horizon B (v/v).[11] Our aim was to replace the standard casing used for A. bisporus cultivation with a casing mixture efficient for growing A. subrufescens and easy to implement by European mushroom growers. Peat/limestone was far less efficient than peat/limestone/sand casing for time to fruiting and biomass production of CA487.[20] Based on this result, our reference casing mixture was A. bisporus casing (peat/limestone) supplemented with fine sand. Under our cultivation conditions, not only did the partial replacement of peat with vegetal charcoal (casing C2 vs C1) cause no improvement in mushroom biomass at the end of the experiment, it also reduced the d1–d30 yield of the two wild strains.

Spent mushroom substrate has also been evaluated as a substitute for peat in Agaricus cultivation. A casing mixture composed of Sphagnum peat/spent mushroom substrate (wheat straw and poultry manure ingredients) 4:1 (v/v) + CaCO3 was as efficient as a peat/lime mixture for A. bisporus productivity.[16] When all strains were taken as a whole, we obtained the worst biomass production with the two casing mixtures (C3 and C4) containing spent compost. In contrast to C3 that reduced the yield of the four strains, the C4 effect varied with the strain. Despite the yield of CA487 being similar with C1 and C4, the casing mixture C1 was chosen because it gave the best yield for all strains. Indeed, our objective was to find the best casing mixture to grow A. subrufescens, irrespective of the strain. Besides, C4 has the same peat/spent substrate/CaCO3 proportion as the casing mixture with which Pardo-Giménez et al.[16] obtained a good performance for an A. bisporus strain. The difference in Agaricus species, the use of several strains and possibly the peat origin and the characteristics of the spent substrate could contribute to explaining why spent compost was not a good material to prepare a standardized casing for A. subrufescens.

The C1 casing mixture used for the different experiments allowed CA487 to produce 171–228 g kg−1 substrate in the d1–d30 period, which fell between the values of 443 and 1315 g per 4 kg substrate that Mata et al.[20] obtained for this strain 30 days after pin formation with casing made of sand/peat/limestone 2:1:1 and 1:1:1 (v/v/v) respectively and substrate based on wheat straw supplemented with sugar cane bagasse. In contrast to their observation, we did not improve the mushroom biomass by increasing the percentage of sand in the casing mixture. The substrate we used, based on wheat straw and horse manure, might explain this difference.

Most air temperatures during incubation reported for experiments performed in Brazil ranged between 25 ± 2 and 28 ± 1 °C.[5, 11, 12, 14] Incubation at a minimum temperature of 8 °C during the night and a maximum temperature of 26 °C during the day was also applied.[21] Our incubation conditions were close to the 22 ± 1 °C used in a Slovenian facility.[6] These temperatures are suitable for the incubation of A. subrufescens and more adapted to cultivation in temperate countries with moderate energy expenditure. The variations in temperature measured in the compost during incubation reflected neither the propensity of the strain to colonize the substrate nor its ability to produce mushroom biomass.

The mushroom can fruit at a temperature between 20 and 30 °C.[22] Although, in contrast to A. bisporus, the almond mushroom does not need a decrease in temperature for fruiting,[23] a reduction in air temperature to 17–20 °C to induce primordial formation followed by an increase to 22–28 °C for the development of the fruiting body was reported.[6, 12, 14, 24-26] However, various experiments performed in Brazil showed that large and uncontrolled variations in temperature also proved suitable. A mushroom yield of 9.6% (strain BZ-04) was obtained after 90 days under natural conditions in an area bordering the Guaramiranga forest, Ceará State (climate predominantly warm and wet) with minimum temperature around 20 °C and high variations in maximum temperature ranging from approximately 20 to 32 °C.[11] Strain CS1 cultivated at Lavras (Minas Gerais State) in a room under natural conditions with the temperature ranging from 17 to 28 °C had a yield of 13.3% at 101 days after casing.[21] More interesting are the Brazilian works showing valuable production in a greenhouse where local climatic conditions directly influenced mushroom yield. Cultivating ABL-97-12 in a plastic greenhouse where minimum, maximum and mean temperatures ranged from 13 to 21 °C, from 23 to 36 °C and from 14.3 to 25.6 °C respectively led to the same yield as in a climatic chamber set at 25 ± 2 °C.[5] Strain ABL-04/49 cultivated in a greenhouse where the air temperature varied between 20.4 and 36.8 °C and the compost temperature between 20.3 and 30.8 °C showed 20% higher yield compared with that obtained in a climatic chamber with primordial induction.[14, 26] Starting from these observations, we decided to investigate whether variations in temperature could improve the productivity of the eight studied strains. The air temperature was regulated to mimic variations between night and day. Minimum and mean temperatures recorded were in the same range as those reported by Braga et al.,[5] but the maximum temperature did not exceed 28.4 °C, while it reached 36 °C in the Brazilian greenhouse. The lack of high temperatures during our experiment could explain the absence of yield improvement. However, the lowest temperature recorded in the compost was 17.5 °C and the highest 26.8 °C, which did not differ markedly from the 20.3 and 30.8 °C measured by Zied et al.[14] in a greenhouse. The only notable difference related to variations in temperature was that CA565 began to fruit earlier than at constant temperature and no longer differed from the other two cultivars for this trait. The Brazilian strains remained far less productive than the European strains, regardless of the experiment.

Precocity is defined as yield at mid-cycle of harvest expressed as a percentage of total harvest and depends on the type of compost and casing.[14] Zied et al.[14] observed precocity ranging from 50 to 62% in a first set of crops and from 69 to 75% in a second set. We chose to assess the percentage of biomasss production during three successive periods of 10 days following the first picking of the strain. The major part of the biomass was obtained during the first 10 days, and production was very low during the last period (d20–d30). The kinetics of production differed dramatically from that known for cultivars of A. bisporus and observed under our cultivation conditions for this species. These observations suggest that the commercial compost used for A. bisporus is probably not the optimal substrate to grow A. subrufescens, but yields obtained with the wild European strains were much better than those reported for commercial strains in Brazil (e.g. 80–110 g kg−1 after 65 days for the strain ABL-97/12[5] and 88 g kg−1 after 70 days for the commercial strain ABL-04/49[14]). The average production in Brazil was estimated to be 8–16% after 120 days of cultivation.[7]

As Colauto et al.[24] reported for two Brazilian cultivars, we observed that changes in mushroom fresh weight during harvest depended on the strain, although all strains except CA643 produced less heavy mushrooms during the d20–d30 period. As regards the whole harvest, Brazilian strains were generally more interesting than wild European strains for individual fresh weight and dry matter content, but this was offset by the far higher yield of the wild strains. In particular, the Spanish strain CA438-A proved to be a good material owing to its classification for fresh weight and dry matter, which did not differ from those of the Brazilian cultivar CA561.

CONCLUSIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

The experiments described herein demonstrate that commercial production of the almond mushroom can be developed in Europe with the substrate commonly used for A. bisporus, a simple modification of the casing mixture (addition of peat and sand) and maintaining the incubation temperature throughout the crop. The use of new strains selected among wild European isolates is promising.

ACKNOWLEDGEMENTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES

This work was supported by the research projects 115790 CONACYT (Mexico) and ANR-09-BLAN-0391-01(France). RC Llarena-Hernández would like to thank CONACYT, Mexico for a scholarship. The authors gratefully thank DC Zied for providing the Brazilian cultivars and Ludovic Devaux for mushroom production.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIAL AND METHODS
  5. Results
  6. DISCUSSION
  7. CONCLUSIONS
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  • 1
    Kerrigan RW, Agaricus subrufescens, a cultivated edible and medicinal mushroom, and its synonyms. Mycologia 97:1224 (2005).
  • 2
    Wasser SP, Current findings, future trends, and unsolved problems in studies of medicinal mushrooms. Appl Microbiol Biotechnol 89:13231332 (2011).
  • 3
    Mizuno T, Kawariharatake, Agaricus blazei Murrill: medicinal effects and dietary effects. Food Rev Int 11:167172 (1995).
  • 4
    Wisitrassameewong K, Karunarathna SC, Thongklang N, Zhao R, Callac P, Moukha S, et al, Agaricus subrufescens: a review. Saudi J Biol Sci 19:131146 (2012).
  • 5
    Braga GC, Montini RMC and Salibe AB, Parâmetros da produção de Agaricus blazei sob differentes condições ambientais de cultivo. Sci Agraria Paranaensis 5:4756 (2006).
  • 6
    Gregori A, Pahor B, Glaser R and Pohleven F, Influence of carbon dioxide, inoculum rate, amount and mixing of casing soil on Agaricus blazei fruiting bodies yield. Acta Agric Sloven 91:371378 (2008).
  • 7
    Zied DC, Minhoni MTA, Kopytowski-Filho J, Barbosa L and Andrade MCN, Medicinal mushroom growth as affected by non-axenic casing soil. Pedosphere 21:146153 (2011).
  • 8
    Wang Q, Li BB, Li H and Han JR, Yield, dry matter and polysaccharides content of the mushroom Agaricus blazei produced on asparagus straw substrate. Sci Hort 125:1618 (2010).
  • 9
    Zhou Q, Tang X, Huang Z, Song P and Zhou J, Novel method for cultivating Agaricus blazei. Acta Edulis Fungi 17:3942 (2010).
  • 10
    Pokhrel CP and Ohga S, Cattle bedding waste used as substrate in the cultivation of Agaricus blazei Murrill. J Fac Agric Kyushu Univ 52:295298 (2007).
  • 11
    Cavalcante JLR, Gomes VFF, Kopytowski-Filho J, Minhoni MTA and Andrade MCN, Cultivation of Agaricus blazei in the environmental protection area of the Baturité region under three types of casing soils. Acta Sci Agron 30:513517 (2008).
  • 12
    Colauto NB, Silveira AR, Eira AF and Linde GA, Alternative to peat for Agaricus brasiliensis yield. Bioresour Technol 101:712716 (2010).
  • 13
    Siqueira FG, Dias ES, Silva R, Tokuda Martos E and Rinker DL, Cultivation of Agaricus blazei ss. Heinemann using different soils as source of casing materials. Sci Agric 66:827830 (2009).
  • 14
    Zied DC, Minhoni MTA, Kopytowski-Filho J and Andrade MCN, Production of Agaricus blazei ss. Heinemann (A. brasiliensis) on different casing layers and environments. World J Microbiol Biotechnol 26:18571863 (2010).
  • 15
    Llarena Hernández CR, Largeteau M, Farnet A-M, Minvielle N, Regnault-Roger C and Savoie J-M, Phenotypic variability in cultivars and wild strains of Agaricus brasiliensis and Agaricus subrufescens. Proc. 7th Int. Conf. on Mushroom Biology and Mushroom Products, Arcachon, Vol. 2, pp. 3849 [Online]. Available: https://colloque4.inra.fr/icmbmp7/Download-proceedings [18 May 2011].
  • 16
    Pardo-Giménez A, Pardo-González JE and Zied DC, Evaluation of harvested mushrooms and viability of Agaricus bisporus growth using casing materials made from spent mushroom substrate. Int J Food Sci Technol 46:787792 (2011).
  • 17
    Braga GC and Eira AF, Productivity of Agaricus blazei Murrill in relation to the cultivation environment, the substrate mass, and the casing layer. Energia Agric 14:3951 (1999).
  • 18
    Bustamante MA, Paredes C, Moral R, Agulló E, Pérez-Murcia MD and Abad M, Composts from distillery wastes as peat substitutes for transplant production. Resour Conserv Recycl 52:792799 (2008).
  • 19
    Eira AF, Nascimiento JS, Colauto NB and Celso PG, Tecnologia de cultivo do congumelo medicinal Agaricus blazei (Agaricus brasiliensis). Agropec Catarín 18:4549 (2005).
  • 20
    Mata G, Calderón GA and Savoie J-M, Effect of casing in production of edible and medicinal mushroom Agaricus subrufescens, in Mushroom Science, Vol. 18, ed. by Zhang J, Wang H and Chen M. China Agriculture Press, Beijing, pp. 743748 (2012).
  • 21
    Siqueira FG, Martos ET, Silva EG, Silva R and Dias ES, Biological efficiency of Agaricus brasiliensis cultivated in compost with nitrogen concentrations. Hort Bras 29:157161 (2011).
  • 22
    Eira AF, Cultivo do Cogumelo Medicinal Agaricus blazei (Murrill) ss. Heineman. Aprenda Facil Ed., Viçosa (2003).
  • 23
    Dias ES, Mushroom cultivation in Brazil: challenges and potential for growth. Review. Ciênc Agrotec Lavras 34:795803 (2010).
  • 24
    Colauto NB, Silveira AR, Eira AF and Linde GA, Production flush of Agaricus blazei on Brazilian casing layers. Braz J Microbiol 42:616623 (2011).
  • 25
    Kopytowski-Filho J and Minhoni MT, Nitrogen sources and C/N ratio on yield of Agaricus blazei, in Science and Cultivation of Edible and Medicinal Fungi, ed. by Romaine P, Keil CB, Rinker DL and Royse DJ. The Pennsylvania State University Press, University Park, PA, pp. 213220 (2004).
  • 26
    Zied DC and Minhoni MTA, Influência do ambiente de cultivo na produção do cogumelo Agaricus blazei ss. Heineman (A. brasiliensis). Rev Energia Agric Botucatu 24:1734 (2009).