Eutrema japonicum is a perennial herb belonging to the Eutrema genus in the crucifer family. In recent years, numerous substances with notable pharmacological activities have been successfully isolated from E. japonicum. Despite significant advancements in related research, the efficacy of the rhizome extract of E. japonicum against root-knot nematodes remains unknown. In this study, the rhizome extract of E. japonicum was used as raw material to demonstrate the inhibitory and nematicidal effects of the extract on Meloidogyne enterolobii. The results showed that the LC₅₀ of the E. japonicum rhizome extract on second-stage juveniles (J2s) was 69.590 mg/mL and 22.336 mg/mL at 24 h and 48 h after treatment, respectively. The mortality rate of J2s reached 88.93% at 48 h post-treatment when the concentration was 200 mg/mL, and the inhibition rate of single-egg hatching reached 88.14%. This study analyzed the chemical composition of the ethanol extract of E. japonicum, and 10 organosulfur compounds and lipid compounds with insecticidal and antibacterial effects were preliminarily screened out. Among them, sec-butyl isothiocyanate and geraniol were further investigated for their nematicidal activity, demonstrating high efficacy against M. enterolobii. Moreover, we conducted network pharmacology analysis and RT-qPCR analysis to predict the potential inhibitory mechanisms of sec-butyl isothiocyanate and geraniol on M. enterolobii. These findings offer a scientific foundation and theoretical framework for utilizing E.japonicum as a potential raw material for developing novel natural plant nematicides.

Yellow leaf disease (YLD) has been the most severe disease threatening areca palm, commonly known in areca palm cultivation. However, it has not yet been systematically studied in terms of the relationship between infected plants and the structure of rhizosphere microbial communities. In order to systematically study the impact of YLD on the rhizosphere fungi of the areca palm, we implemented high-throughput sequencing technology to analyze the microbial community structure and diversity under different disease conditions. The results indicate that as the severity of the disease increases, the diversity of the fungal community diminishes, with species abundance and richness initially decreasing before subsequently increasing, while phylogenetic diversity increases, and significant changes occur in the structure of the soil fungal community. At the phylum level, the dominant fungal phyla in the rhizosphere of areca palm are Ascomycota and Basidiomycota. At the genus level, the dominant genera are Sarocladium, Roussoella, Penicillium, etc., and their relative abundance increases with the severity of the disease. LEfSe analysis revealed that Archaeorhizomyces, Codinaea, and Albifimbria serve as indicator species for healthy areca palms, with their relative abundance trends consistent with changes in Alpha diversity. FUNGuild prediction results indicated that the fungal nutrient type structures of the three rhizosphere samples were highly similar, with saprotrophs being the absolutely dominant type. With the increase in the severity of the disease, the number of harmful fungi in the soil (such as Plectosphaerella, Fusarium, etc.) increases, thereby limiting the sustainable development of the soil. Network analysis indicates that beneficial microbial communities such as Stachybotrys and Roussoella exhibit extensive negative interactions. Therefore, the YLD of areca palm significantly alters the structure and diversity of the rhizosphere fungal community. Simultaneously, some beneficial microorganisms may be recruited by the areca rhizosphere to resist the invasion of YLD by improving the rhizosphere environment and enhancing plant immunity, such as Trechispora, Saitozyma, and Marasmiellus. This experiment is expected to provide a theoretical basis for the study of the rhizosphere microecology of the areca palm, the exploration of excellent biocontrol resources, and the green control of YLD in the areca palm.