In vitro base temperature of Colletotrichum gloeosporioides Penz isolated from avocado (Persea americana Mill.) fruits cv. Hass in Michoacán, México.

Among the phytophatological factors constraining export are anthracnose and scab, distributed in all municipalities in Michoacan, Mexico, where avocados are grown. The objective was to determine the base temperature from which the fungus Colletotrichum gloeosporioides develops under laboratory conditions and its relationship to infections occurring in avocado fruits in the field. Monoconidial cultures were derived from isolates of avocado fruits with anthracnose symptoms, collected in different municipalities and incubated at 4, 7, 8, 9, 10, 13, 15, 16, 18, 24, 27, 30 and 40 °C. Five fruits were selected and the number of new infections was recorded in each fruit. The base temperature of C. gloeosporioides grown on PDA was 8°C (growth rate, r = 0.015), its optimum grow was at 24°C (r = 0.24) followed by 16 and 18°C (r = 0.18) and 27°C (r = 0.17). Fungus did not grow at 4 and 40°C. In the field, there were no fruit injuries when the mean temperature was below 14°C, the same happened when the temperature exceeded 18.9°C. It was also observed that mean temperatures over 15°C increased the number of injuries and between 15.4 and 17.9°C showed the greatest number of injuries.