Study on biological characteristics of Alternaria alternata caused occurrence of pear black spot

Biological characteristics of Alternaria alternata, which causes the occurrence of pear black spot, were studied. The results indicated that there was significant difference in growth characteristics (including: growth rate, quality of spore, color of colony and thickness of colony) in PSA media. The suitable temperature for mycelia growth was 20~30℃, and the optimum was 28℃; the optimum temperature for spores germination was 28℃. The suitable relative humidity of mycelia growth was 50%~100%, and the optimum humidity was 98%~100%; only under high relative humidity condition, spores could germinate; especially in water drop, the germination rate of spores is high. The suitable pH value for mycelia growth was 4~12, and the optimum pH value was 7~8. The pH value of PSA could be changed by A. alternata after culturing. The optimum pH value for spores germination was 7~8. A. alternata could make use of many carbohydrates and nitrogen sources, the optimum carbon source was sucrose, and the optimum nitrogen source was peptone, while(NH4)2SO4 and NH4Cl would inhibit mycelia growth.