Replication and Movement of In Vitro-Generated Infectious RNAs of Potato Mop-Top Virus RNAs in Two Mechanically Inoculated Potato Cultivars

Potato mop-top virus (PMTV), vectored by soilborne protist Spongospora subterranea f. sp. subterranea is increasingly becoming a threat to potato production in the United States. The major means of spread are through infected tubers, vectors, and contaminated farm equipment. Using infectious cDNA clones of PMTV, in vitro-produced viral RNA transcripts were used to mechanically inoculate two potato cultivars differing in their sensitivity to PMTV, as well as model plants Nicotiana benthamiana and N. tabacum, as the virus is known to be mechanically poorly transmitted. Infection was measured using primers to each of the three genomic RNAs by real-time PCR. The movement of all three genomic RNAs and their relative accumulation were studied over several time points. Overall, 100% of the inoculated plants showed infection. All three RNAs of PMTV were detected in younger, uninoculated leaves at 7,14, and 21 days postinoculation, suggesting successful infection followed by long-distance movement. Potato cultivar Clearwater Russet had higher levels of PMTV compared with Castle Russet, which was in agreement with their response to PMTV under natural field conditions. These findings suggest that the use of infectious RNA transcripts in combination with mechanical inoculation is a potential tool for studying PMTV–potato interactions at the omics level. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .