EFFECTS OF LOW TEMPERATURE ON MYCELIAL GROWTH AND SPORE GERMINATION OF BOTRYTIS ALLII IN CULTURE AND ON ITS PATHOGENICITY TO STORED GARLIC BULBS

摘要

Botrytis allii was incubated at 20, 10, 4, 2, 0, -2 and -4 degrees to investigate effects of temperature on growth, sporulation and germination on potato dextrose agar (PDA), and to estimate incidence and severity of disease on garlic bulbs inoculated with the pathogen during storage. B. allii was capable of growing to a colony diameter of 17 mm after 20 weeks, sporulating and germinating on PDA at temperature as low as -4 degrees C. After 12 weeks at -4 and -2 degrees C the mycelial growth was observed only on 45-54% of bulbs wound-inoculated with conidial suspension, and infection was limited to 5 mm in diameter on the surface of inoculation sites without producing any symptoms of the disease. Temperature responses were similar for mycelial growth, conidial germination and infection, but mycelial growth and sporulation was slower and later on garlic bulbs than in culture. Wounds were readily colonized by B. allii. No disease was found on unwounded bulbs that were inoculated with conidial suspensions and with mycelial plugs at various temperatures. Only 1 . 6-9 . 5% of cloves became infected by contact with other cloves within the same bulb after 12 weeks of storage at temperatures of 4-20 degrees C.