EFFECT OF NUTRITION an‎d PHYSICAL FACTORS ON MYCELIAL GROWTH an‎d SPORE PRODUCTION OF Curvularia prasadii, A MYCOHERBICIDE AGENT FOR BARNYARD GRASS (Echinochloa crus-galli) IN RICE

Echinochloa crus-galli is an important weed in rice paddies. The optimum cultural and physical conditions for production of Curvularia prasadii (CP01, CP02, and CP03 isolates), a biocontrol agent for the rice weed, E. crus-galli, were determined. Culture media, light regime, pH, incubation temperature, and aeration were tested for their effect on the mycelial growth and spore production of the fungal biocontrol agent. Showed to be the best medium for the linear growth of the three isolates of the fungus was malt extract agar (MEA). Maximum yield of spores of the three isolates was obtained on potato dextrose agar (PDA). Contentious darkness was the most suitable light regime for the mycelial growth and sporulation of the CP01 and CP02 isolates, while contentious or diurnal light were best for CP03 growth. However, all degrees light regime were sutable for the spore production of the isolate CP03, with no significant differences among them. The pH levels of 6, 7, and 8 induced the highest mycelial growth of the three isolates. However, the latter two pH levels (7 8) were best for the sporulation of all three isolate. The best mycelial growth was obtained at incubation temperature of 30°C (for CP01 and CP03) and 35°C (for CP02). For spore production, the optimum level of temperature for isolates CP01 and CP02 was 35°C, while it was 30°C for CP03. Aeration level (as negatively correlated with the number of Parafilm® layers around the culture plate edge) was also tested. There was no effect of the number of Parafilm® layers (aeration level) on the CP02 mycelial growth. However, two layers of sealing culture plates with Parafilm® provided optimum level of aeration for best mycelial growth for isolates CP02 and CP03 and highest spore production for all three isolates.