Effect of Chemically Disinfected Wheat Straw on the Growth and Yield of Pleurotus Ostreatus Mushroom

We investigated the effect of chemically disinfected wheat straw on the growth and yield of oyster mushroom (Pleurotus ostreatus). Various levels of treatments combined with different time (12, 18 and 24 hours) and dose of Formalin (250, 500 and 750ppm) and Bavistin (75ppm) were used, and the results were compared with the control. Compared to the control, almost all the treatments showed increased values, and among them significantly higher mycelium running rate, the lowest time from stimulation to primordial initiation and to harvest, number of primordial per packet, number of fruiting body per packet were found in treatment consists of 750ppm of Formalin with 75ppm of Bavistin for 18 hours. Length and diameter of the stipe, diameter and thickness of pileus, biological yield, economic yield, dry yield and biological efficiency were also significantly increased in this treatment. Wheat straw treated with 500ppm of Formalin with 75ppm of Bavistin for 18 hours performed best in terms of per cent protein and nitrogen content. However, weight of individual fruiting body Journal of Agricultural Studies ISSN 2166-0379 2018, Vol. 6, No. 1 http://jas.macrothink.org 190 was significantly higher when treated with 250ppm Formalin with 75ppm of Bavistin for 24 hours. As the sterilization of wheat straw using 750ppm of formalin with 75ppm of Bavistin for 18 hours could control pathogens and gave increased yield, this treatment might be useful as an economically effective treatment for the highest yield of oyster mushroom.


Introduction
Mushrooms are large reproductive structure (fruiting body) of edible fungi, and oyster mushroom, Pleurotus ostreatus, is most suited to the climatic condition of Bangladesh and the tropical areas as well. It is a good source of protein, vitamins and minerals (Khan et al., 1981), and at fresh harvest it contains about 85-95% water, 3% protein, 4% carbohydrates, 0.1% fats and 1% minerals and vitamins (Tewari, 1986). Mushroom reduces the diabetes (Anderson and Ward, 1979), serum cholesterol in human bodies that helps in controlling hypertension (Suzuki and Oshima, 1979) on regular feeding. It is a valuable healthy food with low calories, higher vegetable proteins, zinc, chitin, fiber, vitamins and minerals (Alam and Saboohi, 2001). Edible mushrooms are recommended by the FAO as food, to meet protein requirement of developing countries, the large proportion of which depends mainly on cereals (World Bank, 2004).
Oyster mushroom contains 19-35% protein on dry weight basis as compared to 7.3% in rice 13.2% in wheat and 25.2% in milk (Chang & Miles, 1988). It contains 4.0% fat having good quantity of unsaturated fatty acids which are essential in our diet (Holman, 1976). It is rich in essential minerals and trace elements (Chandha and Sharma, 1995) and the amount of niacin, pantothenic acid and biotin are of appreciable level (Subramanian, 1986).The cultivation of oyster mushrooms has become an attractive economic alternative due to its high demand and market value (Chang, 2006).
Because of their high saprophyte characteristics, most Pleurotus species grows on lingo-cellulose materials such as rotten wood, wood chips, and agricultural postharvest residues (Straatsma et al., 2000;Stamets, 2000). Recycling of these unfavorable materials through mushroom culture can increase agricultural efficiency and enhance the degradation processes of lingo-cellulose sources (Obodai et al., 2003). Selection of suitable substrate is necessary to get good growth as they affect the growth, yield, quality and nutritional values (Sarker et al., 2007a). Wheat straw was used successfully as substrate and gave good yields of oyster mushroom (Hoa et al. 2015).
However, the parameters including substrate source, substrate quality, spawn, strain, compost, and complement affects the growth and performance for high yield of oyster mushroom (Royes et al. 2004;Jafarpour et al., 2010). A wide range of disease can cause serious problems in mushroom cultivation, and condition in Bangladesh such as high humidity and warm temperature are favored by many pathogens. Disinfect or pasteurize the substrate is one of the important practice for this disease management (Mushroom growers handbook, 2004).
Chemical disinfection is recommended as it is cheaper than the other sterilization methods such as steam sterilization (Afyon, 1988). And, no residual effects found in mushroom after chemical sterilization. Previously, chemical treatment with 1% formaldehyde together with 2.0% copper sulphate gave satisfactory yields, and but maximum control of green mould in oyster mushroom was obtained when treated with thiabendazole at 5 g/m 2 to the substrate before pasteurization (Jhune et al., 1990). The effects of these fungicides and their optimum concentration were not clear. To overcome this issue, it was necessary to find suitable chemical disinfectant that was easily available with low cost and more yielding with their optimum concentration to control different mycoflora associated with oyster mushroom to increase its yield.
The objectives of this study were to find out suitable time (hours) and dose (concentration) of two easily available fungicide, Formalin and Bavistin, for the sterilization of wheat straw, and their effects on the growth and yield of oyster mushroom. The findingss will be useful for the better cultivation and higher yield of Pleurotus ostreatus

Materials & Method
The experiment was carried out at the Mushroom Culture House of the Biochemistry laboratory in the Department of Biochemistry at Sher-e-Bangla Agricultural University in Dhaka, and the National Mushroom Development and Extension Center (NAMDEC) laboratory in Savar during the period from January to June, 2013. Fruiting body of oyster mushroom was collected from NAMDEC, wheat straw from the local bazaar, and the chemicals were collected from fertilizer shop respectively.

Preparation of Substrates and Sterilization
The collected wheat straw was soaked in the water with chemicals according to the composition of treatments. After the treatment time was over, the straw was taken off and left them on perforated sacs for the removal of excess water. Then the wet straw was spreaeded in clean polythene set on the floor for sun drying, and CaCO3 at a rate of 1% on dry weight basis is mixed with the straw.

Inoculation and Preparation of Spawn Packets
The 400gm of mixed substrates were filled into the 9×12 inches polypropylene bag with 20% mother spawn into three layers. The filled polypropylene bags were prepared by using plastic neck and plugged the neck with cotton and covered with brown paper placing rubber band to hold it tightly in place.

Cultivation of Spawn Packet
The moisture of the culture room was maintained 80-85% relative humidity by spraying water 3 times a day. The light around 300-500 lux and ventilation of culture house was maintained uniformly. The temperature of culture house was maintained 22°C to 25°C. The first primordia appeared 2 to 4 days after scribing depending upon the type of substrate.

Collection of produced mushrooms
The matured fruiting body was identified by curial margin of the cap, as described by Amin (2002). Mushrooms were harvested by twisting to uproot from the base.

Mycelial growth, % (MG):
Mycelial growth was counted by taking the full packet as a full unit and generally the data was taken at every two days intervals.

Mycelium running rate in spawn packet, cm (MRR):
The linear length was measured at different places of packet using the average length of mycelium running for different places (L) divided by number of days (N) following the formula proposed by Sarker, 2004):

Days from stimulation to primordial initiation (DFSPI):
Days required from inoculation to completion of mycelium running were recorded .Percent increase of average number of primordial using the treatment from treatment 2 to 10 over control.

Number & weight of individual fruiting body per packet (NIFPP, WIFPP):
Number of well-developed fruiting body was recorded. Average weight of individual fruiting body was calculated by dividing the total weight of fruiting body per packet by the total number of fruiting body per packet. The overview of the experiment is shown in figure 1.

Dimension (stipe and pileus) of fruiting body (DOF):
Length of the stips (LSt) of three randomly selected fruiting bodies was measured using a slide calipers. Diameter of stipe (DSt), diameter and thickness of pileus (Dpi, TPi) were also Journal of Agricultural Studies ISSN 2166-0379 2018 measured.

Biological yield (BY):
Biological yield per 400 g packet was measured by weighing the whole cluster of fruiting body without removing the lower hard and dirty portion.

Economic yield (EY):
Economic yield per 400 g packet was recorded by weighing all the fruiting bodies in a packet after removing the lower hard and dirty portion.

Dry yield (DY):
The dry yield was calculated using the following formula (Sarker, 2004):

Statistical analysis of data:
All the data collected on different parameters were statistically analyzed by following the analysis of variance (ANOVA) method and mean differences were adjusted by Duncan's Multiple Range Test (DMRT) (Gomez and Gomez, 1984) using the MSTAT-c computer package program. The mean differences among the treatments were compared by least significant difference (LSD) test at 5% level of significance.

Effect on Mycelium Growth
MRR per day for each type of substrates was measured after the mycelium colony crossed the shoulder of the packet. Results showed wide variations among the treatments and almost all the treatments had significantly higher MRR than the control (Table 1). The highest MRR was observed in T7 (0.79cm) and the lowest running rate of mycelium (0.53 cm) was observed in T1 (Table 1). These results corroborated with the previous reports by Jhune et al. (1990), Rai and Vijay (1992), Namdev et al. (2006), Khaliq et al. (2013), but the MRR were comparably higher in these combination of treatments in this study.
The DFSPI was varied greatly among the treatments and took significantly shorter days than the control. The lowest DFSPI was observed in the treatment T7 (6.04 days) and the highest was observed in the treatment T1 (8.57 days). These results corresponded with the previous reports published by Gupta (1989), Khan et al, (2010), Royse (2002), and Amin et al. (2007), but the time required from stimulation to primordial initiation was shorter (6.04 days) than previous reports.

DFPITH
The lowest time from primordial initiation to harvest was recorded in the treatment T7 (3.56 days) and the highest time from primordial initiation to harvest was observed in the treatment T1 (4.66 days) (Table 1). These results showed the shortest DFPITH than the previous studies reported by Dhoke et al. (2001) who found that the days required for first picking varied from 11.25-12.00 and the final picking completed from 42.25 to 43.50 days depending on different substrates.

NPPP
The lowest NPPP was observed from the treatment T1 (53.33) and the highest was found in the treatment T7 (82.67) ( Table 1). The treatment T5 and T6 also showed good performance but not up to the T7. The result of this study corroborates with the study of previous reports

Journal of Agricultural Studies
ISSN 2166-0379 2018, Vol. 6, No. 1 by Amin (2002). Dey (2006) found that the number of primordia of oyster mushroom significantly varied with the variation of substrates used.

NIFPP
The highest NIFPP was observed in the treatment T7 (64.33) and the lowest was in the treatment T1 (33.33) (Table 1). Previously, Yoshida et al. (1993) also reported that the number of fruiting bodies was lower when only wheat straw was used, but increased when the substrates was mixed with wheat bran.

WIFPP
The highest WIFPP was observed in the treatment T8 (3.18) and the lowest was found in the treatment T1 (2.23).The other treatments differed significantly in terms of average weight of individual fruiting body (Table 1). Sarker et al. (2007a) reported the individual weight of fruiting body ranges from 1.33-1.59 g, and in this study, we found that the weight of individual fruiting body ranged from 2.23 to 3.18 g. This was might be due to the effects of disinfection through chemical treatments.

DOF
The highest average length of stipe was observed in the treatment T7 (2.83 cm) and the lowest average length of stipe was in the treatment T1 (2.30 cm). The highest diameter of stipe was observed in the treatment T7 (0.88 cm) and the lowest average diameter of stipe was in the treatment T1 (0.67 cm). The highest diameter of pileus was observed in the treatment T7 (5.71 cm) and the lowest average diameter of pileus was in the treatment T1 (3.50 cm). The highest average thickness of pileus was observed in the treatment T7 (0.85 cm) and the lowest average thickness of pileus was in the treatment T1 (0.66 cm). (Table 2). Ahmed (1998) found that lower diameter of pileus produced the lowest yield and concluded that the diameter of pileus increased the quality and yield of mushroom and highest dry yield from mango sawdust. Habib (2005) found that the diameter of pileus ranged from 4.85 cm to 8.95 cm and thickness of the pileus ranged from 0.45cm to 0.70cm due to different substrates. He also mentioned that the length of stipe of oyster mushroom on different substrates varied from 1.93cm to 2.97cm and the diameter ranged from 0.74cm to 1.05cm.

BY
The highest biological yield was recorded from the treatment T7 (185.8 g) and the lowest biological yield was recorded from T1 (78.09 g). The rest of the treatments differed significant as compared to control (Table 3). Chowdhury et al. (1998) examined and reported the highest yield of oyster mushroom when added 5% additional supplements to the substrates. Dhoke et al. (2001) found significant effect of different agro-wastes on yield of oyster mushroom.

EY
The highest economic yield was recorded from the treatment T7 (179.0 g) and the lowest economic yield was recorded from T1 (73.86 g). The economic yield of the rest of the treatments differed statistically compared to control (Table 3). Amin et al. (2007) found that the trend of economic yield corresponded with different supplements at different level.
Conducting yield values were higher than previous.

DY
The maximum dry yield of mushroom was recorded from the treatment T7 (18.48 g). The lowest dry yield was recorded from T1 (7.74 g). The other treatments differed statistically compared to control (Table 3). This result corroborated with the previous studies (Sarker et al.,2007a;Dey,2006;Domondon and Pope,2000;Shukla and Bishwas,2000;Rab,1999). However, Rab (1999) found after chemical analysis that the methods did not significantly affect the dry matter and composition of P.sajor-caju.

BE
The highest biological efficiency, 105.3%, was observed in the treatment T7 and the lowest biological efficiency, 43.44 %, was observed from T1. The rest of the treatments varied significantly over control (Table 3).Present findings showed the similar tendencies with the previous reports (Biswas et al., 1997;Kalita et al., 1997;, Shukla and Bishwas, 2000). Biswas et al.(1997) and found that supplementation of substrate promoted biological efficiency (125.75%). Kalita et al. (1997) observed biological efficiency for different substrates ranged from 35.2 to 60.9 %. The combination of treatment with the different concentration of Bavistin and Formalin increased the BE than other previous combination.

Conclusions
Oyster mushroom is an important constituent of the diet because of their high energy value and percent (%) of protein. To increase its production, suitable sterilization technique is important. Chemical sterilization is cheaper than other current technique. Based on our results, it can be concluded that Wheat straw treated with 750ppm of Formalin with 75ppm of Bavistin for 18 hours is found to be contributed significantly in yield and yield contributing characters and provided the best results with the highest yield and biological efficiency.
This treatment gave the best results and can be recommended as an economically effective for oyster mushroom cultivation. Besides, the treatment combined with 500ppm Formalin and 75ppm Bavistin for 18 hours may be a fair option for protein content. Further studies using physiological and chemical approaches are necessary to justify the present results. ISSN 2166-0379 2018