Partial characterization of two new viruses in ash belonging to the families Partitiviridae and Caulimoviridae

Authors: BRATSCH, SARA - University Of Minnesota; LOCKHART, BEN - University Of Minnesota; Mollov, Dimitre; TISSERAT, NED - Colorado State University

Submitted to: Acta Horticulture Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2017
Publication Date: 2/28/2018
Citation: Bratsch, S., Lockhart, B., Mollov, D.S., Tisserat, N. 2018. Partial characterization of two new viruses in ash belonging to the families Partitiviridae and Caulimoviridae. Acta Horticulture Proceedings. 1191:89-96.

Interpretive Summary: Ash trees (Fraxinus spp.) are widely distributed through European, Asian, and North American temperate zones. In the U.S.A. ash trees typically occur in mixed hardwood forests and are also used extensively as boulevard and shade trees in municipal and residential landscapes. Additionally the seeds, leaves, and branches are a food source for animals such as game birds, small mammals, deer, and moose. Ash trees are susceptible to many pests and diseases including viruses. In 2014, white ash trees (F. americana) in Colorado were identified with distinct virus symptoms. Symptomatic leaves were examined by transmission electron microscopy and spherical virus-like particles were identified. Next generation sequencing confirmed two viruses previously unknown to infect ash. The characterization of these new viruses infecting ash trees will provide useful information to the ornamental, landscape, and forestry industries.

Technical Abstract: Ash trees (Fraxinus spp.) are widely distributed through European, Asian, and North American temperate zones. There are numerous recently identified pests and pathogens that have killed hundreds of millions of ash worldwide. In 2014, white ash trees in Colorado exhibited symptoms of chlorotic patches that increased in size through the growing season and developed necrotic lesions. Partially purified extracts of symptomatic leaves examined by transmission electron microscopy identified spherical virus-like particles. Next generation RNA sequencing of symptomatic tissue identified five virus-like contigs with similarity to both partitiviruses and caulimoviruses. Primers designed from the putative contigs amplified products of the expected size from both inoculated plants and wild ash seedlings. Further work is required to complete the virus genomes, phylogenetic analysis, complete Koch’s postulates, and determine the distribution of these viruses in the Fraxinus genus.