Maturation of Sporangia of Phytophthora infestans Affecting the Rapidity of Indirect Germination.

Abstract

Sporangial suspensions were prepared from infected potato tuber slices or discs cultured for various periods at different temp. When the suspensions were incubated at 14 deg C, the opt. for indirect germination, sporangia from older cultures germinated more rapidly than those from younger cultures. Newly formed sporangia germinated only slowly, while almost all those aged by pre-incubation at 6 h or more at 22 deg germinated within 1 h when post-incubated at 14 deg . Maturation by aging thus appears essential for indirect germination. The time required for maturation was affected by air temp. during sporangial production and also by the incubation temp. after preparation of the sporangial suspension. The shortest maturation time, c. 6 h, was at 18-22 deg . Temp. <15 deg slowed maturation considerably and >26 deg inhibited it. Matured sporangia soon lost the ability to germinate rapidly when suspensions were incubated at 26 deg or above