Rapid and specific detection of Peronospora belbahrii in basil (Ocimum basilicum L.) using a LAMP assay

Basil downy mildew, caused by the oomycete Peronospora belbahrii, can decrease whole basil crops in days, making it a top concern for basil growers. In this study, a Loop-Mediated Isothermal Amplification (LAMP)-based biosensor was developed for the rapid detection of P. belbahrii in Ocimum basilicum L. A fragment of a gene with unknown function was used as the target sequence to design primers for LAMP reactions. The optimal incubation temperature and time for the most efficient primer set were determined. Under standardized conditions, the LAMP assay exhibited at least 1000-fold higher sensitivity than conventional PCR, detecting attogram levels (1 copy) of synthetic DNA. Detection of the pathogen from genomic DNA (gDNA) of P. belbahrii spores confirmed the sensitivity of the assay. In terms of specificity, the LAMP assay showed negative results for gDNA from pathogenic fungi affecting basil and positive results for gDNA from diseased basil leaves. Finally, the LAMP assay could facilitate the rapid detection and diagnosis of basil downy mildew in infected tissues, providing information on basil health and, consequently, informing decisions regarding control management in O. basilicum fields.