Loop-mediated isothermal amplification assay: A novel disease diagnostics tool in sweetpotato seed quality assurance

Abstract

Sweetpotato is an important food crop in global production. However, sweetoptato viruses pose a threat to sustainable agriculture and cause significant economic loss. More than 30 viruses have been reported to date, with sweet potato feathery mottle virus (SPFMV) and sweet potato chlorotic stunt virus (SPCSV) occurring frequently and in combination, causing sweetpotato virus disease. The detection of viruses directly from sweetpotato is still a challenge, and efforts are being made toward this front. Therefore, rapid detection of viruses is critical for effective control. Current diagnostic tests are not sufficiently sensitive to reliably detect viruses directly from sweetpotato and require expensive laboratory equipment and a high level of skilled experience. Loop-mediated isothermal amplification (LAMP) is sensitive and spe cific for both DNA/RNA amplification; it is affordable and its characteristics make it potentially suitable for on-site testing. LAMP assays have been developed for sev eral sweetpotato viruses: SPCSV, SPFMV, and sweet potato leaf curl virus (and related sweepoviruses). Laboratory validation showed a 100% diagnostic sensitiv ity for all three viruses. The LAMP on-site testing results were comparable to those of polymerase chain reaction and reverse transcriptase polymerase chain reaction confirmatory laboratory tests. Interlab validation and packaging into affordable kits will ensure high adoption in sub-Saharan Africa. The LAMP assay can be used for field surveys and monitoring the phytosanitary status of pre-basic seed production in quarantine or certification program. This guarantees pathogen-free planting material enters the seed system. We discuss opportunities for LAMP as a diagnostic assay for the rapid detection of sweetpotato viruses and its adoption as a quality control system for planting materials