Factors affecting appressorium formation and germination of mango anthracnose fungus.
Chuang T. Y.
Author Affiliation: Department of Plant Pathology and Entomology, National Taiwan University, Taipei, Taiwan.
Plant Pathology Bulletin 6 : 41-48
Abstract : The effect of nutrients, relative humidity (RH), temperature, fungal strains and spore concentration on appressorium formation of Colletotrichum gloeosporioides [Glomerella cingulata] isolated from mango (Mangifera indica) was investigated using a cellophane system. Among the isolates of G. cingulata tested, both conidial germination and appressorium formation were not affected by glucose concentration in the range 0-1000 ppm. Appressorium formation was not significantly different at RH 100% and 98% but there was a significant decrease with decreasing RH. Neither conidial germination nor appressorium formation was observed at RH 90%. Appressorium formation from germinating spores was greatest at 20°C. Both isolates tested and spore concentration had a significant effect on appressorium formation. In addition, dried appressoria formed on cellophane stored at 25°C for 2 weeks were tested. Appressorium germination was higher when the cellophanes were soaked in 1% glucose-0.1% aspartic acid nutrient solution, compared with placing the cellophane on water agar or PDA directly or soaking in the nutrient solution for 2 hours before placing on PDA. Appressorium germination started 12 h after soaking in the nutrient solution and reached a maximum after 30 h incubation. Appressorium germination was maximum after 6 weeks storage of dried appressoria formed on cellophane at 25°C.