Effect of root aqueous extract of Asarum sieboldii on soil nematode community in greenhouse tomato

Abstract Root-knot nematode (RKN, especially Meloidogyne incognita ) is a growing threat to greenhouse tomatoes in China. However, control methods in the greenhouses in China are limited. The use of chemical pesticides such as fluopyram and thiazole phosphate to control M. incognit a is expensive and harmful to the environment. The Chinese herb Asarum sieboldii is commonly used and it shows potential as a plant-derived pesticide. We evaluated the effectiveness of A. sieboldii in regulating the soil nematode community and M. incognita in tomato greenhouses. Combining morphological identification with high-throughput sequencing techniques, we demonstrated that A. sieboldii root extract significantly reduced the relative abundance of plant-parasitic nematodes (PPN) while promoting the ecological and functional recovery of bacterivorous (BF) and fungivorous (FF) nematodes. The aqueous extract exhibited high toxicity against M. incognita J2s and reduced the number of root galls by 69.5% per gram of root, decreased the number of egg masses by 58.4% and enhanced shoot fresh weight by 53.6%. Through column chromatography and HPLC-MS analysis, methyl fumarate (MEF) and methyl gallate (MG) were identified as key active compounds, demonstrating LC50 values of 10.20 mg/L and 49.47mg/L with root-knot suppression rates reaching 64.8% and 61.3% under greenhouse conditions. This study presents the first evidence that A. sieboldii aqueous extract effectively controls M. incognita without compromising the ecological balance of soil, providing a theoretical foundation for developing environmentally-friendly botanical nematicides.