Abstract:
Gymnosporangium species (Pucciniaceae, Pucciniales, Basidiomycota) are the causal agents of cedarapple
rust diseases, which can lead to significant economic losses to apple cultivars. Currently, the genus contains
17 described species that alternate between spermogonial/aecial stages on Malus species and telial stages on
Juniperus or Chamaecyparis species, although these have yet to receive a modern systematic treatment. Furthermore,
prior studies have shown that Gymnosporangium does not belong to the Pucciniaceae sensu stricto (s.str.),
nor is it allied to any currently defined rust family. In this study we examine the phylogenetic placement of the genus
Gymnosporangium. We also delineate interspecific boundaries of the Gymnosporangium species on Malus based
on phylogenies inferred from concatenated data of rDNA SSU, ITS and LSU and the holomorphic morphology of
the entire life cycle. Based on these results, we propose a new family, Gymnosporangiaceae, to accommodate
the genus Gymnosporangium, and recognize 22 Gymnosporangium species parasitic on Malus species, of which
G. lachrymiforme, G. shennongjiaense, G. spinulosum, G. tiankengense and G. kanas are new. Typification of
G. asiaticum, G. fenzelianum, G. juniperi-virginianae, G. libocedri, G. nelsonii, G. nidus-avis and G. yamadae are
proposed to stabilize the use of names. Morphological and molecular data from type materials of 14 Gymnosporangium
species are provided. Finally, morphological characteristics, host alternation and geographical distribution
data are provided for each Gymnosporangium species on Malus.
