Loop-mediated isothermal amplification (LAMP) and suction spore trap-based assay for detection of mildew pathogens Podosphaera xanthii and Pseudoperonospora cubensis in cucurbits

The cultivation of cucurbits in India faces substantial challenges due to powdery and downy mildew diseases, caused by Podosphaera xanthii and Pseudoperonospora cubensis, respectively. Implementation of effective disease management strategies relies heavily on the rapid and early detection of the pathogen responsible for these diseases. Here, we aim to use loop-mediated isothermal amplification (LAMP) and suction spore trap-based assay for effective detection of P. xanthii and P. cubensis. The LAMP primers designed using internal transcribed spacer (ITS)1 and ITS2 and 5.8S ribosomal RNA were found suitable for detecting P. xanthii while the sequence of cellulose synthase 2 (CesA2) gene was effective for P. cubensis. The specificity of the assay to their respective pathogen was further confirmed through the screening of nine different test pathogens: Macrophomina phaseolina, Phytophthora capsici, Fusarium oxysporum, Sclerotium rolfsii, Alternaria alternata, Geotrichum candidum, Aspergillus niger, A. flavus and Colletotrichum gloeosporiodes. Subsequently, a suction spore trap designed using a polyvinyl chloride (PVC) pipe and a cooling fan powered by a solar panel was able to capture the airborne inocula of the two mildew pathogens. In the LAMP assay, air samples from the 16 to 26^th and 23^rd to 29^th standard weeks exhibited positive signals for P. xanthii and P. cubensis, respectively during the 2023 cropping season. Hence, the integration of LAMP assay with suction spore traps is an ideal strategy for the detection of mildew pathogens in cucurbits and will assist in implementing robust disease management practices.