Behavior-based control of Meloidogyne incognita using dimethyl sulfoxide–related sulfoxides in tomato

Abstract

Root-knot nematodes such as Meloidogyne incognita cause severe yield losses in a wide range of crops, and the development of safe and effective control strategies remains an important challenge in agriculture. Dimethyl sulfoxide (DMSO) itself showed no significant nematicidal activity, as it did not alter the mortality of secondstage juveniles (J2). However, when DMSO was applied to soil at approximately 1% (v/v) during tomato infection assays, gall formation was significantly reduced. A notable disadvantage was its negative impact on plant growth. To identify compounds that suppress nematode infection without impairing plant development, we screened 9 DMSO-related derivatives. Five compounds exhibited strong inhibition of nematode attraction in a Pluronic-based assay. Among these, 4-(methylsulfinyl)benzoic acid (4-MSBA), methyl 4-tolyl sulfoxide, and sodium n-octanoate were selected as promising repellency candidates. Subsequent tomato infection experiments revealed that only 4-MSBA effectively reduced gall numbers without affecting plant growth. These findings indicate that 4-MSBA functions as a potent behavioral modulator of M. incognita and represents a promising lead compound for the development of environmentally compatible nematode control strategies. This study does not aim to develop new nematicides or to enhance plant immune responses; rather, it represents a first step toward a novel strategy for suppressing nematode infection by manipulating nematode behavior.