Control of the rootknot nematodemeloidogyne javanicabyBacillus cereus

Abstract

Exposure of Meloidogyne javanica second‐stage juveniles to the bacterium Bacillus cereus in soil inhibited the penetration of the juvenile nematodes into tomato roots. Culture filtrate of the bacterium grown on nutrient broth and tryptic soy broth revealed nematocidal activity on M. javanica juveniles and eggs. Loss of the nematocidal activity of the media by lowering pH, boiling or dialysis raised the possibility that the active ingredient in the culture filtrate was ammonia, released during the breakdown process of peptides in the media by bacterial activity. Free ammonia (NH3) concentrations in the nutrient broth and tryptic soy broth culture filtrates measured after 48 h were 140 and 190 µg ml−1 respectively. Exposure of second‐stage juveniles to 9.3 µg ml−1 ammonia for 40 h in vitro was lethal to 95% of the nematode population. In a nitrate medium, nitrite accumulated up to 250 µg ml−1 during the growth of the bacterium, and its culture filtrate revealed nematocidal activity. The nematocidal activity...