Analogues of dihydrouracil and 9H-purine control Meloidogyne incognita in tomato plants

Abstract

To contribute to the development of new products to control Meloidogyne incognita in tomato plants, the nematicidal activities against this nematode by 35 substances with similar chemical structures to dihydrouracil and 9H-purine were investigated. Initially, the in vitro effect of these substances on the motility and mortality of secondstage juveniles (J2) of M. incognita were evaluated. The most active were 2-pyrazinecarboxylic acid, 5-methyl2-pyrazinecarboxylic acid, orotic acid, 2,3,5-triphenyltetrazolium chloride, methyl pyrazinecarboxylate, and 2,4-diaminopyrimidine. The in vitro lethal concentrations to 50% of M. incognita J2 (LC50) of these compounds, respectively were: 0.85 ± 0.19, 2.8 ± 0.1, 1.3 ± 0.1, 0.32 ± 0.04, 0.55 ± 0.04, and 3.5 ± 0.4 µmol/ml. Under similar conditions, the LC50 for the commercial nematicide carbofuran (2,3-dihydro-2,2-dimethyl-1-benzofuran-7-yl N-methylcarbamate) was 0.70 ± 0.01µmol/ml. When the most active substances were subjected to an assay with tomato (Solanum lycopersicon cv. Santa Clara) plants inoculated with M. incognita, those that most resembled carbofuran were 2,4-diaminopyrimidine, 5-methyl-2-pyrazinecarboxylic acid, methyl pyrazinecarboxylate, and 2,3,5-triphenyltetrazolium chloride. Thus, these analogues of dihydrouracil and 9H-purine are promising for the development of new products to control M. incognita in tomato plants.