Effects of Temperature During Ascus Formation and Frequency of Ascospore Discharge on Pseudothecial Development of Venturia inaequalis. David M. Gadoury, Graduate Research Assistant, Department of Botany and Plant Pathology, University of New Hampshire, Durham 03824. William E. MacHardy, Associate Professor, and Chang-Cheng Hu, Graduate Student, Department of Botany and Plant Pathology, University of New Hampshire, Durham 03824. Plant Dis. 68:223-225. Accepted for publication 6 September 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-223.

The number of asci that developed in pseudothecia of Venturia inaequalis was determined by the temperature between the appearance of ascus initials and the appearance of ascospores. Varying the interval between ascospore discharges had no significant effect on production or maturation of asci when leaves were kept moist and pliable between discharges. There was no evidence of ascospore discharge by means of circumscissile dehiscence or bursting of pseudothecia as noted in some earlier reports. When ruptured pseudothecia were examined, the rupture of the ascocarp wall appeared to be the result, rather than the cause, of senescence.

Keyword(s): apple scab.