A Reverse-Transcription Loop-Mediated Isothermal Amplification Technique to Detect Tomato Mottle Mosaic Virus, an Emerging Tobamovirus

Tomato mottle mosaic virus (ToMMV) is an emerging seed-transmissible tobamovirus that infects tomato and pepper. Since the first report in 2013 in Mexico, ToMMV has spread worldwide, posing a serious threat to the production of both crops. To prevent the spread of this virus, early and accurate detection of infection is required. In this study, we developed a detection method for ToMMV based on reverse-transcription loop-mediated isothermal amplification (RT-LAMP). A LAMP primer set was designed to target the genomic region spanning the movement protein and coat protein genes, which is a highly conserved sequence unique to ToMMV. This RT-LAMP detection method achieved 10-fold higher sensitivity than conventional RT-polymerase chain reaction methods and obtained high specificity without false positives for closely related tobamoviruses or healthy tomato plants. This method can detect ToMMV within 30 min of direct sampling of an infected tomato leaf using a toothpick and therefore does not require RNA purification. Given its high sensitivity, specificity, simplicity, and rapidity, the RT-LAMP method developed in this study is expected to be valuable for point-of-care testing in field surveys and for large-scale testing.