Nuclear Division in Germinating Aeciospores and its Taxonomic Significance for the Western Gall Rust Fungus, Peridermium Harknessii

Abstract

We examined nuclear division of germinating aeciospores of the western gall rust fungus, Peridermium harknessii (teleomorph, Endocronartium harknessii). Mature aeciospores were primarily (86%) binucleate. Migration of the two nuclei into the germ tube followed emergence of the germ tube. The percentage of germlings with 3 nuclei increased from 5% at 4 h to 32% at 12 h; thus, nuclear division in the germ tube was asynchronous and mitotic. We conclude that the fungus is an imperfect rust, and not an endocyclic rust, and should be called Peridermium harknessii. Western gall rust is a common disease on numerous species of hard pines. The life cycle, and hence the appropriate nomenclature and taxonomic classification of the fungus, has been disputed. The most common spore type is produced