Two negative-stranded RNA viruses infecting citrus are representative members of the novel genus Coguvirus

"Abstract: Citrus concave gum-associated virus (CCGaV) and citrus virus A (CiVA) are two negative stranded RNA (nsRNA) viruses recently identified in citrus plants. They have a bipartite genome, composed of an RNA1 encoding the RNA-dependent RNA polymerase in the negative strand and an ambisense bicistronic RNA2 coding for the nucleoprotein and the putative movement protein. Due to the unique structural and phylogenetic features with respect to other nsRNA viruses, these viruses have been proposed to be the representative members of a new genus (Coguvirus), whose final approval by the International Committe for Taxonomy of Viruses is pending. Molecular signatures in the viral genomic RNAs and in the encoded proteins, together with phylogenetic tree reconstructions based on Maximum Likelihood and Bayesian Markov Chain Monte Carlo analyses support a modular genome evolution for these viruses that possibly originated from an invertebrate-infecting ancestor. While CCGaV has been associated with a severe disease (citrus concave gum disease) first described in the early 1930s, the possible association of CiVA with symptoms needs further investigation. To this aim a multiplex RT-PCR protocol to detect simulataneously the two viruses has been developed and validated. Results of a preliminary field survey in Southern Italy (Campania and Apulia Region) showing the presence of both viruses in several citrus species, in both single and mixed infections, will be presented. Non-Technical Summary: Two novel viruses have been identified in citrus trees. One of this virus has been associated with a citrus disease (concave gum disease), the other one has not been associated to any disease so far. The two viruses are closely related to each other from a molecular point view so that they have been proposed to be two novel species in the same new genus. The available molecular information allowed to develop specific multiplex detection methods that will be useful for further investigation on epidemiology and pathogenesis of these infectious agents."