Calocybe Indica is a small genus of about 40 species of mushroom, including St. George’s mushroom and milky mushroom, which are edible and cultivated in India. Very less species of this genus are growing in Britain. The name is derived from the Ancient Greek term kalos “pretty” and cubos “head”. Around nine species are found in subtropical regions. Mushroom is broadly defined as “a macro fungus with distinctive fruiting body which can be either epigeal or hypogeal; large enough to be seen with the naked eye and to be picked up by hand (Chang and miles, 1992). The mushroom comprises a large heterogeneous group having various shapes, size and colors. All are quite different in characters, appearance and edibility. White milky mushroom (C. indica) is an edible mushroom having white  sporophore, large sized  fruiting bodies and delicious flavor. Mushroom could tolerate high temperature ranges of 25-35°C with a biological efficiency of 60-70% under optimum conditions. Their sporocarps have long shelf-life. This mushroom contains most of the mineral salts required by the human body, such as potassium, sodium, phosphorus, iron and calcium (Chang and Millis, 2004), due to its alkaline ash and high fibre content, it is highly suitable for people with hyperacidity and constipation (Doshi et al., 1988).

It was essential to investigate the physiological requirements and colony characters of this fungus in culture before going its large scale cultivation. Hence the present investigation was carried out to observe the effect of temperature and pH on mycelial growth and colony characteristics of different strains of C. indica.

Effect of different temperatures on mycelial growth of strains of C. indica

From the data (Table 2) all the strains showed maximum mycelial growth at 30°C followed by 25°C and minimum at 35°C on 4^th, 6^th and 8^th day. However, on 2^nd day some of the strains like CI-5 and CI-6 showed maximum mycelial growth at 25°C while that of other strains were at 30°C. The mycelial growth of the each strain was varied significantly at all the tested temperatures (Bhugarski et al, 2002). At 30°C, on 8^th day strains CI-7 showed maximum full diametric growth of mycelium (9.0 cm). The other strains showed significant variation to each other giving diametric growth ranges from 6.4-8.7 cm (with average growth rate of 0.80-1.09 cm per day). Then the strain in order to superiority was CI-7 giving 6.56 cm mycelial growth. At par growth was recorded from the strain CI-5 and CI-6 however CI-10 produces minimum growth. The least growth of the strains was recorded at temperature 35°C on which highest mycelial diametric growth was (5.40) obtained for CI-5. The minimum growth of 3.8 and 3.9 cm was recorded from CI-10 and CI-9 respectively. These results are in accordance with the findings of Doshi and Sharma (1995), Furlan et al. (1997). They reported optimum temperature range between 20 - 35°C for the mycelial growth of C. indica.

Effect of different pH on mycelial growth of strains of C-indicia

The data (Table 3) shows that the maximum diametric mycelial growth was at pH 8.0 followed by at 7.0. The minimum mycelial growth for all the strains was observed at pH level 6.0 and 9.0. At pH 8.0, the strain CI-7 has completed its growth on the 8^th day that is 9.0 cm. The next strains in order to superiority was CI-10. The poor mycelial growth was recorded in the case of strain CI-5, that is 6.8 cm which was near with the growth obtained for strains CI-9 and CI-8. It was observed that the strains CI-9 grew faster at all the tested pH.  At pH 7 the strains showed diametric growth ranges from 6.40 - 8.30 cm. The growth pattern of the strains at pH 7.0 was similar to pH 8.0 but at slow growth rate. The results are in accordance with the finding of Khan et al. (1991) which reported pH 7.0 as the most suitable pH level for radial mycelial growth of the Lentinula edodes.

Colony characters of different strains of C. indica

All the six strains were grown on malt extract Agar (MEA) medium to study their colony character viz., colony appearance, color, shape and margin. From the data (Table 1), two types of colony viz., fluffy and cottony were observed among the strains. Fluffy growth appeared for strain CI-5, CI-7, CI-9 and CI-10 while strains CI-6 and CI-8 showed cottony appearance. All the strains showed white colour of colonies. Shape of the colonies varied from circular to irregular. All the Strain showed circular colony except CI-9 which showed irregular colony. Margin of colonies were observed: even and uneven types. The strains CI-5, CI-6, CI-7, CI-8 and CI-10 showed even margin whereas and CI-9 showed uneven margin of the colonies.

 The results obtained are in accordance with the finding of Jin and Xu (1990), Goltapeh and Kapoor (1989). They reported fluffy and apprised types of the colonies of Agaricus bisporus. Bahukhandi et al. (1991) observed the differentiation in colony characters of strains of A. bisporus in respect of colony diameter, appearance, color, shape, zonation, margin, sectoring, pigment and exudates formation.

Present investigations have been helpful in understanding the physiological requirements and colony character of different strains of this fungus. These preliminary studies are being extended for the cultivation trials of C. indica.

The growth rate of mycelium was evident at high values of temperature (even tends to infinity) using the above mathematical expressions. It helps us to define further growth rate by statistical assignments. These expressions can be solved in algebraic and differential equation because the Laplace transform provides the facility to define any function from zero to infinity in continuous and piece wise continuous manners.

The author(s) have not declared any conflict of interests.