Detection of viable ascospores of Neosartorya

Studies on 29 Neosartorya cultures showed that many ascospores, as enumerated in a haemocytometer, failed to produce colonies when cultured on agar media. Although the percent recoveries differed greatly between spore crops, germination and outgrowth of most were stimulated by heat activation in grape juice for 30-60 min at 70°C. Most probable number and CFU counts were usually similar which indicated that low recoveries were not due to an inadequate incubation period or to the production of self-inhibitory compounds. Low percent recoveries did not affect the D values obtained in heat-resistance trials.