The activity of amino acids produced by Paenibacillus macerans and from commercial sources against the root-knot nematode Meloidogyne exigua

The rhizobacterium Paenibacillus macerans was grown in tryptic soy broth and after separating the cells by centrifugation the activity of fractions of the supernatant was tested against Meloidogyne exigua juveniles. From HPLC analyses and spectral data, the most active fractions were found to contain alanine, glutamic acid, glycine, histidine, threonine and valine, which were probably produced by bacterial hydrolysis of proteic nutrients. Amino acids from commercial sources were then assayed to confirm these results and to evaluate their potential for the control of nematodes. LC₅₀ of 26 and 283 μg ml⁻¹ were shown for the nematicide aldicarb and L-cysteine respectively when tested on M. exigua juveniles. At a concentration 38.4 times>LC₅₀, the amino acid diminished the nematode population on coffee plants to values statistically equal to those obtained with aldicarb at a concentration 19.2 times>LC₅₀.