Pleurotus sajor-caju,
an edible mushroom belonging to order Agaricales of class Basidiomycetes is
most promising mushroom, coming next to button mushroom in respect of its
production at global level sharing 25 per cent of total world production.
Although, it is not valid oyster species (Guzmán, 2000), even then it is as
nutritious as other valid taxa which makes it an ideal food for human
consumption. In India, it is admired
especially due to its excellent flavour, taste and above all, easy method of
growing without any sophisticated infrastructure. For the growing of Pleurotus spp. paddy straw is found most
common and efficient substrate (Ram, 1995; Dubey, 1999; Gupta et.al., 1999; Siddhant et. al.,
2009) which is accompanying indigenous micro flora. The antagonistic
interaction between these micro flora and desired fungus contributed the low
productivity of mushroom (Bhandari and Singh, 1983; Sharma and Jandaik, 1980,
1981a, b and 1982; Shiddique et.al., 2004). Therefore, proper substrate disinfection
is pre-requisite to eliminate weed and obtained good yield. It can be achieved
by various methods (Arya and Arya, 2003; Bahukhandi, 1990; Champawat and
Chitale, 2003; Kumar et. al., 1990; Ram and Thakur, 2005; Tewari and
Pandey,1988).
In present
communication, six months stored paddy straw was used for the cultivation of Pleurotus sajor-caju to evaluate the effect of following substrate preparation methods on the biological efficiency of this
mushroom species.
1) Autoclaving (T1): This method included sterilization of substrate at 15 lbs pressure for 60 minutes (Tewari and Panday, 1988).
2) Hot water application (T2): In this method, paddy straw was boiled in the water for one hour at 100°C (Diana
et. al., 2006).
3) Radiation treatment (T3): In this treatment, the straw substrate
was exposed to U.V. light for 1 hour 30 minutes (Ram and Thakur, 2005).
4) Chemical treatment (T4): Paddy
straw substrate was pasteurized in the solution of
Formaldehyde (500ppm) and Bavistin (75ppm) for 18 hours as suggested by Vijay
and Sohi (1987).
5) Water (T5): Substrate was not
pasteurized at all and it was only soaked in water for 24 hours.
The substrate disinfected by employed
techniques, viz., T1,T2,T3 and T4 showed quick spawn run, primordial initiation
and fruit body maturation than control [T5] (Table). The crop of P. sajor-caju was harvested in three
flushes where yield and biological efficiency ranged 10-360 g and 02-72%,
respectively. All the substrate preparation methods showed highly significant
yield and biological efficiency over control (unpasteurized sets). It was
recorded the maximum in chemical pasteurization (360 g, 72%), followed by
autoclaving (340 g, 68%), hot water treatment (335 g, 67%) and radiation
treatments (305 g, 61%). The unpasteurized sets gave negligible result
(10g, 2%) in aforesaid manifestations (Fig). Among the treatments, chemical pasteurization was
found most significant. The hot water treatment and autoclaving was considered
as second best treatment which was pat par to each other.
During the course of
study, two fungal species belonging to Ascomycetes (Peziza sp.) and Basidiomycetes (Coprinus
spp.) were encountered on the mushroom beds. The unpasteurized beds, used
in triplicate were severely infected by Coprinus
spp. and Peziza spp. (Plate) which
resulted in great loss in mushroom yield. The bed contaminated with Peziza spp. could not produced even a
single fruit body. The higher decomposition of substrate was also noticed in
unpasteurized beds.
The results revealed
that disinfection techniques played a crucial role in minimizing the loss of
production and biological efficiency (Fig) this also protects the beds from
competitors.
The disinfection
methods reduce the natural micro flora of substrate and improve substrate
colonization and yield of mushroom. Due to this reason, pasteurized substrates
showed quick mycelial run and higher sporophore formation. In respect of yield
performance, chemical treatment gave significant response. This was because of
the fact that chemical treatment permitted a minimum number of bacterial
population which favoured the growth and production of more cellulase by Pleurotus
spp. and thereby increased the yield (Krishnamoorthy et. al., 1991). Production of this enzyme is directly proportional
to the yield of Pleurotus in vitro (Kochuthresiamma et al., 1991;
Nallathambi and Marimuthu, 1994). Besides this, bacterial population actively
corrodes the surface of the substrate providing more suitable site for the
colonization of fungus. Pleurotus spp. are also reported to utilize the nitrogen fixed by N- fixing
bacteria present in the substrate. In addition, chemical treatments slightly
modified the nature of substrate and favoured the growth of fungal mycelium. As
compared to chemical treatment, autoclaving and Hot water treatments gave
insignificant response. This was due to higher temperature which eliminated all
the beneficial microorganisms present in the substrate (Bano et al.,
1979). Unpasteurized beds gave highly insignificant result in respect of
reduction in yield and biological efficiency than pasteurized ones. It is well
known that stored straw is an easy source of contaminants which competes with
mushroom mycelium for the available nutrients. The loss in yield was either due
to depletion of food material from the substrate required for growing mushroom
mycelia or through the production of toxic substances by the microorganisms
(Atkins, 1949). Although, Doshi and Singh (1991) stated that toxic metabolites
produced by microorganisms are very mild and has little inhibitory effect on
growth of Pleurotus sajor-caju and whatever effect is seen was because
of depletion of nutrients from the medium due to contaminants. The higher
decomposition of substrate was also visible in unpasteurized beds. It might be
the combined action of contaminating microflora and cultivated fungus.
During the cultivation of Pleurotus sajor-caju two types of
competitor were encountered on mushroom beds. This result was supported by the
conclusions given by different workers which revealed the presence of weeds
associated with oyster mushroom cultivation (Vijay and Sohi, 1987, Siddique et
al., 2004). No or lesser appearance of competitors in pasteurized substrate
revealed the efficiency of treatments. Chemical treatment was effective against
fungal competitors which is agreement with the finding of Champawat and Chitale
(2003) and Pervez et. al., (2009) who reported formaldehyde and bavistin
combination as a best pasteurization practice. The effectiveness of hot water
and autoclaving methods was due to the high temperature that kills the foreign
inoculums from the substrate while ultraviolet light in the range from 200 to
300nm affects the growth of the competitors. Direct exposure of UV radiation is
lethal to their DNA.(PDF Copy)
Cite this as: Siddhant, Swapanil Yadav, Rupali Mishra and Ruchira Singh, (2014): Effect of substrate disinfection on the biological efficiency of Pleurotus sajor-caju (Fr.) Singer Plant Archives 14(1):205-209.