Study on Systemic Acquired Resistance in Arabidopsis thaliana Induced by Weed Extracts

Plant defense activators need to induce systemic acquired resistance (SAR) in order to protect crops by enhancing their inherent disease-resistance mechanisms. In order to screen for plant species that contain active substances as plant defense activators, seven weed extracts, which were previously demonstrated as potential plant defense activators inducing SAR in a bioassay using cucumber plants (Cucumis sativus L.) and Colletotrichum orbiculare, were evaluated for their SAR-inducing potential using SAR marker genes in Arabidopsis thaliana. Additionally, we evaluated extracts of three oxalate-rich species that are closely related to the giant knotweed (Fallopia sachalinensis), which is used as a plant defense activator. The results revealed that the expression of SAR marker genes, PR1 and PR5, was higher in A. thaliana plants treated with seven tested weed species, namely, Pueraria montana, Trifolium pretense, Boehmeria nivea, Sedum japonicum, Gamochaeta purpurea, Silene armeria, and Fallopia japonica, than those treated with the water control. The extracts of these weeds have the potential to function as defense activators and SAR inducers.