Low-temperature biology and pathogenicity of Penicillium hirsutum on garlic in storage

Penicillium hirsutum grown on potato dextrose agar and kept at 20, 10, 4, 2, 0, -2 and -4 degrees C for 25 weeks revealed a longer lag phase at 0 degrees C and below, and its growth was reduced as the temperature was lowered. At -4 degrees C, the fungus showed slight lengthening of the hyphae only after 19 weeks. Sporulation and germination of conidia were also delayed by low temperatures, and at -4 degrees C there was no production or germination. All of the wounded and inoculated cloves of 'Bianco Piacentino' garlic showed symptoms of blue mould disease after four weeks of storage at temperatures between 0 and 20 degrees C. At -2 degrees C, P. hirsutum colonised all of the cloves after seven weeks, while at -4 degrees C they were all still healthy after 16 weeks. No freezing injury was encountered at negative temperatures. A storage temperature of -4 degrees C is advisable for the prevention of blue mould disease.