Effect of temperature and relative humidity on germination and germ tube development of Mycosphaerella fijiensis var. difformis

Jacome, L.H.; Schuh, W.; Stevenson, R.E.

Effect of temperature and relative humidity on germination and germ tube development of Mycosphaerella fijiensis var. difformis

1991

Jacome, L.H. | Schuh, W. | Stevenson, R.E.

Conidia (three isolates) and ascospores (one isolate) of Mycosphaerella fijiensis var. difformis germinated at 20-35 C. Germination followed a quadratic response function on temperature (R(2) = 0.90-0.98), with an estimated optimum at 26.5 C. Maximum germination was observed in free-water and decreased at lower relative humidities (RH). Conidia germinated over a wider range of RH (92-100%) than ascospores (98-100%). Ascospores germinated earlier than conidia. The highest number of germ tubes per conidium was at 25 C for two isolates and at 30 C for the third isolate in free-water after 24 h. The number decreased at lower RH. Maximum length of germ tubes from ascospores occurred at 30 C (91-95 micrometers) followed by 25 C (68-75 micrometers), with an estimated optimum at 27.7 C. Germ tube length was similar at 100% RH and in free-water, but decreased at lower RH. Differences among the isolates and the possibility of some degree of natural variability in the response of the fungus to environmental factors are discussed.

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