Effect of Various Substrates on Growth and Yield Performance of Oyster Mushroom ( Pleurotus ostreatus ) in Chitwan , Nepal

An experiment was conducted at Rampur, Chitwan, Nepal to find out the growth and yield performance of oyster mushroom (Pleurotus ostreatus) in Completely Randomized Design (CRD).The treatment includes the four different substrate i.e. paddy straw (100%), maize cob+ paddy straw (1:1), sugarcane bagasses+paddy straw (1:1) and sawdust+ paddy straw (1:1). The parameters taken for the observation during the experiment were colonization period, fruit initiation period, length of stalk, diameter of stalk, diameter of pileus, fresh weight of the first and second flush of mushroom and also the biological efficiency (BE) of various substrates. Among the used substrates, the time for colonization and fruit initiation was found to be shorter in case of the paddy straw i.e.18.25 days and 21.75 days respectively. However, the length of stalk was highest in sugarcane bagasses+paddy straw (1:1) i.e.6.10 cm, but the diameter of stalk and pileus were highest in paddy straw i.e.0.80 cm and 7.90 cm respectively. Similarly, the biological efficiency was found to be highest in case of the paddy straw (96.29688 %) followed by maize cob+paddy straw (1:1), sugarcane bagasses+ paddy straw (1:1) and sawdust+ paddy straw (1:1) respectively.


Introduction
Mushrooms are one kind of edible fungi belonging to the genus Pleurotus under the class Basidiomycetes (Mondal et al. 2010).Oyster mushroom (Pleurotus ostreatus) is an edible mushroom having outstanding flavor and taste.Recently, its importance and nutritive value has been realized and well utilized in human consumption diet.There are several species of Pleurotus identified in the world.Most of them are suitable for cultivation.Some Pleurotus species are Pleurotus ostreatus, Pleurotus columbinus, Pleurotus florida, Pleurotus salignus, Pleurotus It was discovered that several species can grow on lignocelluloses, forest by-products and agricultural wastes (Carrera, 1998).Mushroom substrate may be defined as a kind of lignocellulose material which supports the growth, development and fruiting of mushroom (Miles, 1998).Oyster mushroom may be grown on wide range of plant waste as substrate e.g.sawdust, paddy straw, sugarcane baggage, corn stalk, corn cobs, waste cotton, leaves and pseudo stem of banana, water hyacinth, duck weed, rice straw etc. does not require costly processing method and enrichment material (Quimio, 1980;Chow, 1980;Bano et al., 1979).However the experiment was conducted on rice straw and banana leaves at various compositions with a view to determine the cheapest substrate with best yield performance (Mondal et al., 2010).These mushroom substrates must be adjusted to a pH range of 6 to 8 by adding gypsum (Kong, 2004).
Ecological requirements of oyster mushrooms vary at the various stages of growing period.The optimal temperatures for growing mycelia and pin forming are between 20 to 30 0 C and 10 to 20 o C respectively.Substrate moisture should be 60 to 75%, but it should be 80 to 95% during the fruiting, because 80% or over of the fruit body is water (Nadir et al, 2016).Pleurotus ostreatus is different from the other cultivated mushroom which prefers a low level of light during its growth.Oyster mushroom naturally grows in the forest and since the forest light is bluish, fluorescent light can be used for lighting (Kong, 2004).

Spawn Source
The wheat grain spawn of Pleurotus ostreatus was obtained from the commercial mushroom growing farm situated near the Agriculture and Forestry University (AFU).

Preparation of Substrates
The various types of substrates used during the experiment were paddy straw, maize cob, sugarcane bagasses and sawdust.The paddy straw and maize cob were obtained from the Agronomy farm of University, sawdust was brought from the nearby furniture industry and sugarcane bagasses was obtained from the juice seller which were situated near to University.Among those substrates paddy straw and sugarcane bagasses were chopped into the small pieces of about 5 cm long.Similarly, the other two substrates i.e. maize cob and sawdust were grinded to make the fine structure.Thus, prepared substrates were then soaked into the water for about 3.5 hours.After that, the each substrate were packed into the separate large sized bag and stream sterilized.The substrate were treated in the stream water tank for about 4 hrs then allowed to cool in the clean and disinfected surface (using calcium carbonate).

Bagging of Substrates and their Maintenance
After cooling the substrates, polythene bags (50cm x 30cm) were filled.During the bagging, spawn was kept on every 6cm thick layer of the substrate.Around five thick layers were made and spawn was kept in between the every layer of the substrates (@ 125gm/bag).The mouth of the plastics bag were then closed tightly and pores were made on the each plastic bag.The treatments like maize cob+ paddy straw, sugarcane+ paddy straw and sawdust+ paddy straw, were prepared by thoroughly mixing them at 1:1 ratio and then used for bagging.The bags were then kept under the dark mushroom growing house.The inside temperature (20-30 o C) and relative humidity (80-90%) were maintained at various growing stages of mushroom by hanging the wet jute bags around the wall of the house and keeping the floor wet.Water was sprayed about 4-5 times a day on the jute bag and floor.After proper colonization and initiation of the fruiting body, about 4-5 vertical cut were made on the each packed plastic bag using sharp blade for the proper growth and development of the mushroom.

Harvesting, Data Collection and Analysis
The mushroom was harvested with the help of sharp knife as they attained the proper size.The data regarding to the period of colonization and fruit initiation, fresh weight of harvested mushroom at first and second flushes, diameter of pileus and stalk and length of stalk were taken.BE was calculated as fresh weight of harvested mushrooms (g) / dry weight of substrate × 100 (Pokhrel, 2016).
Finally, the analysis of the data was carried out using Microsoft Excel and R-STAT software.Standard procedures followed for recording and analyzed the data on different yield parameters and means were compared using LSD test at 5% level of significance (Bhuiyan et al., 2008).

Colonization and Fruit Initiation Period
The period required for the colonization was found significantly highest for the maize+paddy straw (20.50 days) which was statistically at par with sugarcane bagasses+paddy straw (20.00 days), whereas significantly lowest for the paddy straw (18.25 days) which was statistically at par with sawdust+paddy straw (19.00 days) respectively as shown in Table 1.
Similarly, period required for the fruit initiation was found significantly highest for the sugarcane bagasses+paddy straw (23.25 days) and lowest for the paddy straw(21.75days) respectively as shown in Table 1.

Length of Stalk, Diameter of Stalk and Pileus
The length of the stalk was found significantly highest for the sugarcane bagasses+paddy straw (6.10 cm) which was statistically at par with maize cob+paddy straw (5.79 cm) and paddy straw (5.56 cm) respectively.However, length of stalk was found significantly lowest for the sawdust+paddy straw (4.70 cm) as shown in Table 2.
The diameter of stalk was found significantly highest for the paddy straw (0.80cm) and lowest for sugarcane bagasses+paddy straw (0.63cm).Similarly, the diameter of the pileus was found significantly highest for the paddy straw (7.90 cm) which was statistically at par with maize cob+paddy straw (7.50 cm) and lowest for the sugarcane bagasses+paddy straw (5.30 cm) which was statistically at par with sawdust+paddy straw (5.75 cm) respectively as shown in Table 2.

Fresh Weight and Biological efficiency
The total fresh weight of the first and second flush was found significantly highest for maize cob+paddy straw (718.7 gm) followed by sugarcane bagasses+paddy straw (527.8 gm), sawdust+paddy straw (459.0 gm) and lowest for paddy straw(408.3gm)respectively as shown in the Table 3.
The period for spawn running (colonization) was ranged from 18.25-20.5days in our experiment which was similar to the study carried out by Ahmed (1998), who also reported spawn running of P. ostreatus completed within 17-20 days on different substrates.The variation in the number of days taken for a spawn to complete colonization of a given substrate is a function of the fungal strain, growth conditions and substrate type (Chang & Miles, 2004).Similarly, the period for the pin head formation (fruit initiation stage) was found to ranges from 21.75-23.25 days in our experiment which was also found similar to the study carried out by Fan et al. (2000), they reported pin-head formation of oyster mushroom cultivated in different substrates ranged from 20-23 days.
The colonization period was found lower for rice straw (paddy straw) followed by sugarcane bagasses and sawdust, as shown in the experiment conducted by Sharma, et al.,(2013).Similar result for colonization was found for paddy straw but in case of other two, the period was shorter for sawdust followed by sugarcane bagasses in our experiment.These two substrates were used by well mixed with the paddy straw at the ratio 1:1, which results the lesser time for colonization on those substrates as compared to their experiment, where they used those substrates solely without mixed with paddy straw.The main function of rice straw is to provide a reservoir of cellulose, hemicelluloses and lignin which is utilized during the growth and fructification (Yildiz et al., 2002) Pleurotus ostreatus showed the better yield performance in paddy straw (100%) with respect to the dry weight of the substrate as compared to other.Khadka & Parajuli (2013), has explained that paddy straw is suitable substrates for Pleurotus ostreatus, which was also proved by our experiment.The increase in the yield of mushroom in paddy straw is due to easier way of getting sugars from the cellulosic substances (Ponmurugan, Sekhar, & Sreeshakti, 2007).Whereas, sawdust and sugarcane bagasse also contain high amount of lignin.Low degradation of lignocellulosic substances of sawdust by P. ostreatus might be another factor affecting the overall low yield values from sugarcane bagasse and sawdust (Sharma et al.,2013).

Conclusion
From the present study it can be concluded that paddy straw alone is the best substrate for the growth and development of the oyster mushroom (Pleurotus ostreatus).So, paddy straw solely can be used for its higher production as compared to other supplements like sawdust, maize cob and sugarcane bagasses.Further studies can be done thoroughly modification of environment making suitable temperature and humidity for the better growth and development of oyster mushroom.

Table 1 :
Time taken for colonization (days) and fruit initiation (days) of mushroom on various substrates.
(Figure in a column having common letter(s) does not differ significantly at 5% level of significance.)

Table 2 :
Measurements of length of stalk (cm), diameter of stalk (cm) and diameter of pileus (cm) of mushroom on various substrates.

Table 3 :
Effect of substrates on fresh weight of first flush (gm) and second flush (gm), total fresh weight (gm), dry weight (gm) and biological efficiency (%) of the various substrates.