Efeito de terpenos purificados de Euphorbia sp. sobre Meloidogyne javanica

Abstract

Plant-parasitic nematodes cause great damage to world agriculture, especially Meloidogyne genus, known as root-knot nematodes, considered the most important in the world. The management sustainable practices search has intensified due to growing concern by society for measures that preserve the environment and bring food secure. Using botanical nematicides is a control promising measure. Thus, this study aimed to evaluate the nematicidal activity of terpenes purified from Euphorbia sp. against Meloidogyne javanica. The experiments consisted of evaluating effects of these compounds on mortality and hatch of second-stage juveniles (J2) of M. javanica in vitro. The tests were separated in two stages to evaluate the effect on mortality. Initially, the J2 were treated with the different compounds in the initial concentration of 25 µg mL-1, and the percentage of dead J2 was accounted for after 24, 48, and 72 h of incubation. Then, the initial concentration of each compound was diluted and the following 1.75, 3.5, 6.5, 12.5, and 25 µg mL-1 concentrations were analyzed. These different concentrations were evaluated on J2 of M. javanica to align a regression model to define the lethal concentrations that killed 50 % (LC50) and 95 % (LC95) of the populations in 24 h. For hatch tests, M. javanica eggs were treated with the LC95 of each compound. The number of J2 hatched was daily accounted for eleven days. The control treatments used were distilled water and aqueous solution of tween 5 % (negative controls), and 17.5 mg mL-1 of carbofuran (positive control). Flat bottom plates from 96 wells were used, and each well represented an experimental unit. A completely randomized design with five replicates was used in both experiments. All compounds showed nematicidal activity in the mortality test with more than 95 % mortality after 24 h of incubation. All compounds had an effect on J2 hatching suppression, with reduction rates of 70.1 to 96.1 % as compared to the 5 % tween control. Therefore, it is concluded that the Euphorbia sp. terpenes have a toxic action on M. javanica, showing potential of its use for nematode control.