Characterisation and Distribution of Karaka Ōkahu Purepure Virus-A Novel Emaravirus Likely to Be Endemic to New Zealand.

Arnaud G Blouin,Colleen M Higgins,Lee O Rabbidge,Robin M Macdiarmid,Kar Mun Chooi

doi:10.3390/v13081611

Abstract

We report the first emaravirus on an endemic plant of Aotearoa New Zealand that is, to the best of our knowledge, the country’s first endemic virus characterised associated with an indigenous plant. The new-to-science virus was identified in the endemic karaka tree (Corynocarpus laevigatus), and is associated with chlorotic leaf spots, and possible feeding sites of the monophagous endemic karaka gall mite. Of the five negative-sense RNA genomic segments that were fully sequenced, four (RNA 1–4) had similarity to other emaraviruses while RNA 5 had no similarity with other viral proteins. A detection assay developed to amplify any of the five RNAs in a single assay was used to determine the distribution of the virus. The virus is widespread in the Auckland area, particularly in mature trees at Ōkahu Bay, with only occasional reports elsewhere in the North Island. Phylogenetic analysis revealed that its closest relatives are pear chlorotic leaf spot-associated virus and chrysanthemum mosaic-associated virus, which form a unique clade within the genus Emaravirus. Based on the genome structure, we propose this virus to be part of the family Emaravirus, but with less than 50% amino acid similarity to the closest relatives in the most conserved RNA 1, it clearly is a novel species. In consultation with mana whenua (indigenous Māori authority over a territory and its associated treasures), we propose the name Karaka Ōkahu purepure virus in te reo Māori (the Māori language) to reflect the tree from which it was isolated (karaka), a place where the virus is prevalent (Ōkahu), and the spotted symptom (purepure, pronounced pooray pooray) that this endemic virus appears to cause.

Highlights

Karaka (Corynocarpus laevigatus) is an endemic tree occurring naturally in the coastal and lowland forests of Aotearoa New Zealand’s North Island [1]
Based on fossilised wood and pollen layers within soil, karaka is recorded as having been present in New Zealand for more than five million years [2], the frost-sensitive tree likely only survived in northern parts of the country during glacial periods [3]
Virus-like symptoms on several karaka leaves were identified on a single tree at the Plant & Food Research MARC site in Auckland

Summary

Introduction

Karaka (Corynocarpus laevigatus) is an endemic tree occurring naturally in the coastal and lowland forests of Aotearoa New Zealand’s North Island [1]. Based on fossilised wood and pollen layers within soil, karaka is recorded as having been present in New Zealand for more than five million years [2], the frost-sensitive tree likely only survived in northern parts of the country during glacial periods [3]. It is the only species of the family Corynocarpaceae indigenous to New Zealand, with other members being in New. Caledonia, Vanuatu, Papua New Guinea and Australia (Queensland and northern New. South Wales) [4] Karaka means ‘orange’ as an adjective in the Māori language to describe the color of its fleshy fruit, while the Latin genus name is taken from its ‘club seed’, and the Latin species name describes its ‘smooth’ fruit [3,5]. Preparation through steaming and soaking in running streams allows the kernel to be eaten

Methods

Results

Conclusion