Life cycle and taxonomy of Chrysomyxa succinea in China and phylogenetic positions of Caeoma species on Rhododendron

Abstract

Rust diseases of spruce and rhododendrons caused by Chrysomyxa succinea are commonly observed in forests of northern and eastern Asia. The heteroecious life cycle of this species alternating between spermogonial and aecial stages on Picea jezoensis and uredinial and telial stages on Rhododendron aureum is confirmed for the first time in China by inoculations and phylogenetic analyses. Morphological characters of all stages are described based on specimens obtained from the field and from inoculations. Based on morphological similarities and phylogenetic analyses, Ch. zhouniensis reported on Picea asperata is treated as a synonym of Ch. succinea. Four Caeoma species on Rhododendron are included in the same phylogenetic group as species of Chrysomyxa. Therefore, these species are treated as Chrysomyxa, and four new combinations in Chrysomyxa are proposed.