Novel degenerate primer sets for the detection and identification of emaraviruses reveal new chrysanthemum species

In-silico prediction of RT-qPCR-high resolution melting for broad detection of emaraviruses

Twenty-four species of RNA viruses contain members infecting economically important crops that are classified within the genus Emaravirus, family Fimoviridae. There are at least two other non-classified species that may be added. Some of these viruses are spreading rapidly and cause economically important diseases on several crops, raising a need for a sensitive diagnostic technique for taxonomic and quarantine purposes. High-resolution melting (HRM) has shown to be reliable for the detection, discrimination, and diagnosis of several diseases of plants, animals, and humans. This research aimed to explore the ability to predict HRM outputs coupled to reverse transcription-quantitative polymerase chain reaction (RT-qPCR). To approach this goal a pair of degenerate genus-specific primers were designed for endpoint RT-PCR and RT-qPCR-HRM and the species in the genus Emaravirus were selected to framework the development of the assays. Both nucleic acid amplification methods were able to detect in-vitro several members of seven Emaravirus species with sensitivity up to one fg of cDNA. Specific parameters for in-silico prediction of the melting temperatures of each expected emaravirus amplicon are compared to the data obtained in-vitro. A very distinct isolate of the High Plains wheat mosaic virus was also detected. The high-resolution DNA melting curves of the RT-PCR products predicted in-silico using uMeltSM allowed saving time while designing and developing the RT-qPCR-HRM assay since the approach avoided extensive searching for optimal HRM assay regions and rounds of HRM tests in-vitro for optimization. The resultant assay provides sensitive detection and reliable diagnosis for potentially any emaravirus, including new species or strains.

Complete nucleotide sequence of chrysanthemum mosaic-associated virus, a novel emaravirus infecting chrysanthemum

Here, we report the complete genome sequence of chrysanthemum mosaic-associated virus (ChMaV), a putative new member of the genus Emaravirus. The ChMaV genome comprises seven negative-sense RNA segments (RNAs 1, 2, 3a, 3b, 4, 5, and 6), and the amino acid sequences of its RNA-dependent RNA polymerase (RNA1), glycoprotein precursor (RNA2), nucleocapsid protein (RNA3), and movement protein (RNA4) showed the closest relationship to pear chlorotic leaf spot-associated virus. Phylogenetic analysis showed that it clusters with emaraviruses whose host plants originate from East Asia.