US (PA): Seminar on persistent viruses in peppers

There are many non-pathogenic viruses that are maintained in a persistent lifestyle in plants. Plant persistent viruses are widespread, replicating in their hosts for many generations. Endornaviridae is the only family in this group with a single-stranded RNA genome, the rest have double-stranded RNA genomes. Partitiviridae is the most common persistent virus family in plants. Peppers (Capsicum spp.) are native to Central and South America, and as domesticated plants human selection accelerated their evolution. Bell pepper endornavirus (BPEV) and Capsicum frutescens endornavirus 1 (CFEV 1) have been identified from bell peppers and Tabasco, respectively. Also, Jalapeño and Hungarian Wax peppers have been reported with Pepper cryptic virus 1 (PCV 1) and Pepper cryptic virus 2 (PCV 2), respectively, members of the Partitiviridae.

We investigated the evolution of these persistent viruses in different peppers including C. annuum, C. chinense, C. frutescens, C.bacccutum, and C. pubescens. In addition, by using single nucleotide polymorphisms, the pepper, host populations, and phylogenies were analyzed. The endornaviruses phylogeny was congruent with its Capsicum species host. In this study BPEV was limited to C. annuum species, and phylogenies identified two clades that correlated with the host pungency. No C. annuum infected with CFEV 1 was found in this study, but it was recovered from other Capsicum species. Both partitiviruses were detected in cultivated and wild C. annuum. These two partitiviruses showed a remarkably slow evolution rate in comparison with acute RNA viruses.

Finally, some potential beneficial effects of persistent virus were examined. PCV 1 infected Jalapeño plants deterred aphids (Myzus persicae) which is in a stark contrast to insect-plant interactions in acute virus infections. Aphid reproduction on PCV 1 infected plants was more than two fold lower than virus free plants. This study demonstrated a beneficial relationship between PCV 1 and Jalapeño plants by protecting the plants from the vector of acute viruses. In addition, the effect of PCV 1 on the Jalapeño's developmental growth was tested, and PCV 1 showed no significant effect on the developmental growth of Jalapeño plants.

Source: Penn State University