Optimisation of Growth Parameters of Bipolaris maydis (Nisikado and Miyake) Shoemaker Causing Southern Leaf Blight of Corn (Zea mays L.)

Environmental conditions greatly influence the growth and sporulation of the pathogen. Knowing the unfavourable environment for the growthof a pathogen can be utilized as the basic information in developing appropriate strategies to prevent disease occurrence and for the management. Therefore, a study was conducted to determine the appropriate media and growth conditions for in vitro growth of Bipolaris maydis (Nisikado and Miyake) Shoemaker. Among the seven different media tested Potato Dextrose Agar favoursmaximum mycelial growth and Richard's Agar medium supported maximum sporulation of B. maydis. Maximum dry mycelial weight of B. maydis gradually increased from third day and reached maximum on 9^th day. Due to autolysis of the fungus declining trend was showed from 11^th day onwards. Several environmental factors viz., temperature, pH, relative humidity and light intensity against B. maydis were investigated. The optimum temperature, pH, RH for the growth of B. maydis was found to be 25°C, 8 and 90%. Exposure of the fungus to continuous light period resulted in maximum mycelial growth and continuous darkness favours maximum sporulation of B. maydis. The colony characteristics viz., colony colour, appearance, margin and zonation were measured. The colour of mycelium was ranging from hyaline, light grey, grey, dark grey and black. The colony appearance was rough to smooth, regular to irregular margin withor without zonation. The proper combination of environment conditions may be useful in disease management in the field as well as in the storage.