Impact of Cultivated Hosts on the Recombination of Cucumber Mosaic Virus.

Cucumber mosaic virus (CMV) is one of the most successful viruses known, infecting over 1,200 species of plants. Like other single-stranded RNA viruses, CMV is known to have a high potential for population diversity due to error-prone replication and short generation times. Recombination is also a mechanism that allows viruses to adapt to new hosts. Host genes have been identified that impact the recombination of RNA viruses by using single-cell yeast systems. To determine the impact that the natural plant host has on virus recombination, we used a high-recombination-frequency strain of CMV, LS-CMV, which belongs to subgroup II, in three different cultivated hosts: Capsicum annuum cv. Marengo (pepper), Nicotiana tabacum cv. Xanthi nc (tobacco), and Cucurbita pepo cv. Black Beauty (zucchini). The recombination frequency was calculated by using an RNA 3 reporter carrying restriction enzyme sites created by introducing silent mutations. Our results show that the recombination frequency of LS-CMV is correlated with the infected host. The recombination events in pepper were 1.8-fold higher than those in tobacco and 5-fold higher than those in zucchini. Furthermore, we observed the generation of defective RNAs in inoculated pepper plants, but not in tobacco or zucchini. These results indicate that the host is involved in both intra- and intermolecular recombination events and that hosts like pepper could foster more rapid evolution of the virus. In addition, we report for the first time the production of defective RNAs in a CMV subgroup II isolate.IMPORTANCE Recombination is an important mechanism used by viruses for their diversification and to adapt to diverse hosts. Understanding the host role in the mechanisms of evolution is important for virus disease management and controlling the emergence of new strains. This study shows the impact that cultivated hosts are playing in the evolution of CMV. Furthermore, our results and previous studies show how some specific hosts could be an ideal environment for the emergence of new viral strains.