Active Substances against Meloidogyne exigua Produced in a Liquid Medium by Bacillus megaterium

Abstract

In order to contribute to the development of new methods to control plant-parasitic nematodes, this work aimed to identify active substances against Meloidogyne exigua produced by Bacillus megaterium, which was previously selected due to its ability to produce nematicidal substances. Consequently, the bacterium was grown in tryptic soy broth, from which cells were removed to afford a liquid that was freeze-dried. The resulting residue was fractionated by solvent extractions and chromatographic processes monitored by mortality assays with M. exigua second stage juveniles (J2 ) to select the active fractions in each step. As a result, a fraction causing high mortality of J2 was obtained. According to analyses by infrared spectroscopy and high performance liquid chromatography, this fraction comprised threonine, glutamic acid, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine and histidine. The amino acids L-phenylalanine, L-isoleucine, DL-methionine, L-leucine and DL-valina, obtained from commercial sources, caused significantly higher M. exigua J2 mortalitiesthan those observed for the negative control (water), confirming the nematicidal activities observed for thesubstances from bacterial source