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 specific 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 several sweetpotato viruses: SPCSV, SPFMV, and sweet potato leaf curl virus (and related sweepoviruses). Laboratory validation showed a 100% diagnostic sensitivity 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.

Harnessing potato and sweetpotato innovations for resilient and healthier agri‐food systems in Africa

“…The two sweetpotato papers in this sub-theme focus on viruses, many of which contribute to significant yield reduction. In "Loop-mediated isothermal amplification (LAMP) assay: A novel disease diagnostics tool in sweetpotato seed quality assurance," Wanjala et al (2024) present the successful validation of LAMP assay for three major viruses in East Africa and its potential use in field surveys and for monitoring the phytosanitary status of pre-basic seed production. Mmboyi et al (2024) report the prevalence of sweet potato virus 2 (SPV2) and sweet potato chlorotic stunt virus (SPCSV) in three provinces of South Africa and the determination of the sequence variability in the coat proteins of SPV2 isolates.…”