Zygospore initiation, development and germination in Phycomyces blakesleeanus

Abstract

The effects of low temperature, light and starvation upon zygospore initiation and development in Phycomyces blakesleeanus Burgeff were studied. Sexual structures were initiated, but did not mature, and partially developed game-tangia matured slowly, but normally, at 1°C. Continuous diffuse or feeble light was optimum for initiation and development, but continuous intense light was nearly completely inhibitory. The result of starvation was production of fewer and smaller but otherwise normal zygospores. The influence upon germination of growth factors, heat and cold treatments, the state of maturity, and of short and long-term ageing were studied. Indole-actic acid and gibberellic acid were ineffective in pretreatments or as substrate adjuncts. Germinations were obtained from 70% of immature zygospores forthwith and from 30% of mature zygospores following at least 8 months ageing at 1°. Any one germ sporangium contained exclusively spores of one mating type, either plus or minus. Mycelial germinations frequently occurred; in a single instance such a germination appeared to be heterocaryotic for sexual reaction. Evidence is submitted for transgressive genetic segregation for quantitative mating capacity.