A rapid tool for quantification of latent infection of wheat leaves by powdery mildew

Wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is an important disease worldwide. Detection of latent infection of leaves by the pathogen in late autumn is valuable for estimating the inoculum potential to assess disease risks in the spring. We developed a new tool for rapid detection and quantification of latent infection of seedlings by the pathogen. The method was based on recombinase polymerase amplification (RPA) coupled with an end-point detection via lateral flow device (LFD). The limit of detection is 100 ag μL-1 of Bgt DNA, without noticeable interference from either other common wheat pathogens or wheat material (Triticum aestivum). It was evaluated on wheat seedlings for this accuracy and sensitivity in detecting latent infection of Bgt. We further extended this RPA-LFD assay to estimate the level of latent infection by Bgt based on imaging analysis. There was a strong correlation between the image-based and real-time PCR assay estimates of Bgt DNA. The present results suggested that this new tool can provide rapid and accurate quantification of Bgt in latently infected leaves and can be further development as an on-site monitoring tool.