Ultrastructure and Ornamentation of Puccinia carduorum Urediniospores and Teliospores

Abstract

Scanning and transmission electron mi- croscopy were used to describe the nature and mode of development of surface ornamentation of uredin- iospores and teliospores of Puccinia carduorum pro- duced on Carduus thoemeri. Spines (echinulations) were restricted primarily to the apical 2/3-3/ of uredin- iospores. The basal 14-1/3 of the spore surface was de- void of spines except for two, small, distinct zones; those were: (i) numerous small spines within the hi- lum region encircled by (ii), a single, or sometimes double, ring of larger spines distributed around the base of the spore, located approximately where the spore surface was previously contiguous to the perim- eter of the pedicel apex. The ring of large spines and the small spines within the hilum region perhaps fa- cilitate separation of the spores from the pedicels. All types of urediniospore spines observed appeared to follow a developmental path similar to that described in other rusts. Urediniospores having thicker walls than typical urediniospores were often observed, al- though the distribution of spines was similar on both types of urediniospores. Teliospores were covered with numerous, short, wart-like verrucae having sim- ilar electron opacity as the rest of the spore wall. Pri- or to their appearance on the surface of mature te- liospores the verrucae were present within the matrix of the wall of immature teliospores.