Efficacy of 2-undecanol produced by Paenibacillus polymyxa KM2501-1 in controlling Meloidogyne incognita

Root-knot nematodes (RKNs) are notoriously challenging to control because of their broad host spectrum and swift proliferation. Consequently, there is an urgent need to develop safe and effective nematicides. Microorganisms and their metabolites have the potential to control RKNs safely and effectively. Paenibacillus polymyxa KM2501-1 can produce a range of volatile organic compounds (VOCs) with nematicidal activities, among which 2-undecanol is a potential biocontrol agent against Meloidogyne incognita. Nonetheless, the mechanism by which 2-undecanol prevents RKN infection in plant roots remains unclear. 2-Undecanol has many activities against M. incognita in vitro, including contact (LC50 = 34.5 mg/L), fumigation (LC50 = 191.6 mg/L), attraction, locomotion inhibition (frequency of head thrash and body bend reduced by 84.0% and 97.0% at concentration of 40 mg/L) and egg hatching inhibition (by 98.5% at concentration of 80 mg/L). Upon treatment with 2-undecanol, a noticeable reduction in the number of galls was observed, and the control efficacy reached 60.8% at the dose of 5 mg/pot. Metabolomics analysis revealed that the application of 2-undecanol significantly influenced the composition of root exudates of tomato. Among the 17 differential metabolites, the up-regulated 10-undecenal could attract and kill M. incognita J2 larvae at a concentration of 100 mg/L, and cyclohexylamine had nematicidal activity at the concentration of 1,000 mg/L. This study revealed the mechanism of 2-undecanol inducing plant roots to secrete nematicidal substances with attractant activity, effectively controlling RKNs, which could pave the way for the development of environmentally friendly and cost-effective nematicides.