Resistance Induction and Direct Antifungal Activity of Some Monoterpenes against Rhizoctonia solani, the Causal of Root Rot in Common Bean

This study was conducted to evaluate eco-friendly control agents (carvone, cuminaldehyde, and linalool) against Rhizoctonia solani, which causes root rot disease either by induction of defense response or direct antifungal activity. The induction of resistance was examined by detecting the transcription of defense genes and the effect of the tested control agents on the growth and the yield of common bean plants. The growth of R. solani was significantly inhibited after treatment with the tested compounds compared to the untreated control under laboratory conditions. The disease severity of root rot was decreased in common bean plants treated with the tested compounds compared to untreated control plants under greenhouse conditions. Common bean plants treated with the tested control agents expressed defense genes (Phenylalanine ammonia lyase and β-1,3-Glucanase) involved in jasmonic acid (JA) and salicylic acid (SA) signaling pathways with 2–5 fold higher than the control. Treatment of common beans with the tested control agents and fungicide significantly improved the growth and yield characteristics of common bean. Therefore, the use of monoterpenes could be a novel strategy to control this pathogen and consider the first report.