Exotic and indigenous viruses infect wild populations and captive collections of temperate terrestrial orchids (Diuris species) in Australia

Abstract

Four species of Diuris temperate terrestrial orchids from wild and captive populations were tested for the presence of polyadenylated RNA viruses. The genomes of three exotic viruses were determined: two potyviruses, Bean yellow mosaic virus and Ornithogalum mosaic virus, and the polerovirus Turnip yellows virus. The genomes of five indigenous viruses were detected, including four novel species. They were the potyvirus Blue squill virus A, another potyvirus, two proposed capilloviruses, and a partitivirus. Partitivirus infection is of interest as this group of viruses is also associated with endophytic fungi (mycorrhizae) that are necessary for the germination, growth, development of many terrestrial orchids. Sequence divergence data indicate post-European, pre-European, and endemic origins for these viruses via inoculum from introduced and native plants. The implications of the findings of this study for orchid conservation, and particularly reintroduction programs where viruses may be spread inadvertently to wild populations from infected propagation sources, are discussed.