Plantago lagopus extract as a green fungicide induces systemic resistance against Rhizoctonia root rot disease in tomato plants

Abstract

Extensive use of chemical control agents and fungicides typically leads to numerous risks to human health and the environment. Using plant extracts as natural substances represents a dual key for the environment and sustainable food production, as it reduces the input of synthetic pesticides into the environment and/or controls plant pathogens. For the first time, a <i>Plantago lagopus</i> ethanolic extract has been characterized and evaluated for its protective and curative effects against <i>Rhizoctonia solani</i> in tomato plants. The results showed that <i>P. lagopus</i> extract (10 μg/ml) completely inhibited <i>R. solani</i> mycelial growth <i>in vitro</i>. At 20 days of post fungal inoculation, the results demonstrated that using <i>P. lagopus</i> extract (100 μg/ml) <i>in vivo</i> enhanced tomato plant growth by significantly increasing shoot and root parameters in protective and curative treatments. Furthermore, the protective and curative treatments significantly reduced the disease index by 18.66 and 38.66%, respectively. Induction of systemic resistance with upregulation of <i>PR-1</i> and <i>PR-2</i> and a significant increase in the transcriptional levels of <i>PR-3</i> and <i>CHS</i> in all <i>P. lagopus</i> extract-treated tomato plants were reported compared to untreated plants. HPLC analysis showed that the most common polyphenolic components detected in <i>P. lagopus</i> extract were rutin (74206.3 mg/kg), naringenin (2388.74 mg/kg), quercetin (1249.13 mg/kg), and <i>p</i>-hydroxybenzoic acid (1035.87 mg/kg). In addition, the ellagic acid (798.47 mg/kg), vanillic acid (752.55 mg/kg), catechol (648.89 mg/kg), cinnamic acid (332.51 mg/kg), ferulic acid (296.32 mg/kg), benzoic acid (295.95 mg/kg), and chlorogenic acid (116.63 mg/kg) were also reported. Our study is the first to show that <i>P. lagopus</i> extract can help plants fight off <i>R. solani</i> fungal infection. Furthermore, the findings imply that using the <i>P. lagopus</i> extract as a natural biocontrol agent could be a sustainable strategy to manage plant fungal diseases.