EFFECT OF TEMPERATURE AND HUMIDITY ON THE GERMINATION AND GROWTH OF LASIODIPLODIA THEOBROMAE (PAT.) GRIFF. & MAUBL., CAUSE OF STEM-END ROT OF MANGO (MANGIFERA INDICA L.)

摘要

The effects of temperature and relative humidity on the germination and growth of Lasiodiplodia thcobromac were studied in viiro. Spore germination started at 15°C and significantly dropped at 40°C. A positive correlation of germination with temperature was observed up to 35°C. One-celled spores germinated more rapidly than the two-celled spores in all temperatures tested except at 15 and 40°C. A higher percentage germination was generally accompanied by longer growth of the germ tubes. The longest germ tubes were produced by the one-celled spores incubated at 30°C. There was no variation in the thermal death point (TDP) of three isolates of the fungus collected from three different areas in Laguna and Batangas, The TDP of spores of two-week old cultures was 53 and 54°C from three-week old cultures. The germination of spores and growth of the germ tubes significantly increased with the increasing relative humidity (RH). The minimum RH required for germination was 95%. Maximum germination andgerm tube growth were recorded at 100% RH. The percentage germination and growth rate of one-celled spores were higher than the two-celled spores in all RH tested. A longer incubation period always produced higher germination and germ tube growth.