In vivo and in vitro study of the effects of entomopathogenic bacteria and their filtrates on Meloidogyne incognita

Abstract

Symbiotic bacteria associated with entomopathogenic nematodes produce compounds with antibacterial and antifungal activity. In the present study, Xenorhabdus spp. and Photorhabdus spp. were cultivated in culture medium (in vitro) and in Galleria mellonella (L.) infected with entomopathogenic nematodes (in vivo), and the effect of their filtrates on the mortality of Meloidogyne incognita second stage juveniles (J2s) was investigated. The bacteria filtrates obtained by media culture and hemolymph were associated with different species of entomopathogenic nematodes and placed in direct contact with J2s of M. incognita. The mortality of the juveniles was estimated after 24 h. After dilution of the hemolymph from infected G. mellonella, the filtrates obtained from the in vivo culture and in vitro culture produced an 80% and 20% mortality rate, respectively. Thus, the quality of substances with nematicidal activity was affected by the technique used to cultivate the bacteria, reflecting the difference between cultivation in vivo and in vitro and the importance of the insect host.