Morphological Development and Nuclear Behavior in the Genus Taphrina

Abstract

The developmental morphology and cytology of the parasitic phase of Taphrina carveri Jenkins, T. virginica Sadeback, T. ulmi (Fkl.) Johanson, T. deformans (Berk.) Tulasne and T. populi-salicis Mix have been studied. The development of the mycelium and ascogenous layer has been described for each of the above spp. In T. virginica, the hymenium is formed from a colony of budding yeast-like cells rather than fragmentation of ascogenous mycelium. Three patterns of nuclear behavior have been found to exist among these spp. Taphrina carveri, T. ulmi and T. deformans have a pattern of nuclear behavior which is representative of spp. that have asci with stalk cells and 8 ascospores. In these spp., an equational division of the fusion nucleus precedes meiosis with 1 nucleus migrating into the basal portion of the ascus which is cut off in the formation of the stalk cell. At maturity, the stalk cell becomes empty through the disintegration of its contents. The ascus nucleus undergoes meiosis and ascospore formation. The fusion nucleus of T. virginica, which lacks a stalk cell, undergoes immediate meiosis without a prior equational division. Following meiosis of the ascus nucleus in Taphrina populi-salicis, the haploid nuclei undergo numerous mitotic divisions before spore formation, resulting in the production of many ascospores. The chromosome number in all spp. studied was found to be 2 in the haploid and 4 in the diploid condition. Taphrina ulmi has been reported on Ulmus crassifolia for the 1st time.