Plants can trigger their systemic resistance by receiving chemical cues from neighbors attacked by herbivores or pathogens. In this study, the possibility of conferring resistance from donor tomato plants (Solanum lycopersicum L.) infected with Fusarium oxysporum f. sp. lycopersici (FOL) to receiver neighbor tomato plants via common mycorrhizal networks (CMNs) of Funneliformis mosseae was studied. A split-root system was exploited to avoid direct pathogen-mycorrhizae interaction in donor plant. Our results showed that signal transduction from donor to receiver plant led to an increase in disease resistance through the expression rate of three defense-related genes of phenylalanine ammonia-lyase (PAL), pathogen-related protein (PR1a) and proteinase inhibitor II (PI II) in neighbor plants. Mycorrhizal network established between donor and receiver plants after six weeks. The expression level of all three marker genes significantly increased in receiver plants compared to the control in 0 (T1), 48 h (T2) and 72 h (T3) after pathogen inoculation to receiver plants. The relative gene expression for PI II, PAL and PR1a increased 14.3, 17.98 and 8.49-folds at T1, 69.82, 40.24 and 65.54-folds at T2 and 47.85, 48.10 and 25.79-folds at T3, respectively. The disease intensity index and the area under the disease progress curve (AUDPC) in the CMNs-connected receiver plants were reduced by 66.7 and 69.84%, respectively, compared to the control without CMNs connection. Our findings indicated that F. mosseae CMNs like an underground communication channel could transmit warning signals and activate defense reactions in healthy plants before disease incidence, representing a promising strategy for priming and resistance induction in plants.
