Molecular Characterization of Ti Ringspot Associated Emara Virus and the Development of Assays for Its Detection

Abstract

Ti ringspot disease (TRD) is an emerging virus-like disease of ti plants (Cordyline fruticosa L.) spreading throughout the Hawaiian Islands. Foliar symptoms include chlorotic lesions constricted by secondary veins or circular ring-spots that can coalesce into amorphous lesions. A degenerate reverse transcription (RT)-PCR assay targeting the polymerase gene of known emaraviruses amplified a product from the RNA of symptomatic but not asymptomatic ti plants. The RT-PCR products were sequenced and found to represent a new virus species, designated ti ringspot associated virus (TiRaV). Next generation sequencing of a double-stranded RNA library provided additional sequence information on TiRaV, allowing the development of detection assays able to reliably detect TiRaV and further associate it with TRD. Phylogenetic analyses of this sequence data revealed that TiRaV forms a clade with the emaraviruses Raspberry leaf blotch virus and High Plains wheat mosaic virus in the unassigned plant virus genus Emaravirus.