Efficacy of entomopathogenic nematodes, their associated bacteria and toxins on the development of Meloidogyne incognita on brinjal

Abstract

Research was conducted on two important groups of nematodes plant parasitic nematodes (RKNs) and insect parasitic nematodes (entomopathogenic nematodes). Eggplants (Solanum melongena L.) are the most seriously affected by Meloidogyne incognita. Entomopathogenic nematodes i.e. Steinernema glaseri, S. asiaticum, Heterohabditis indica and H. bacteriophora were evaluated at different time of application against M. incognita for invasion, development and reproduction of M. incognita. In a life cycle study, S. asiaticum and H. bacteriophora were proved more effective in influencing the life cycle of RKNs at all application times than S. glaseri and H. indica. However application of entomopathogenic nematodes before application of M. incognita proved more effective than with and after the application of root knot nematodes. S. asiaticum and H. bacteriophora delayed penetration of nematode juveniles (J2) into roots of brinjal. Cells and toxins of and Xenorhabdus spp. and Photorhabdus spp. proved nematoxic to M. incognita. Higher concentrations of bacterial cells suspensions and toxins were more effective in suppression of hatching of eggs and immobilization of juveniles than the lower concentrations. Percentage inhibition of eggs and juvenile’s immobilization of M. incognita increased with increase in concentration. At concentration of 4x10 7 cells/ml, Xenorhabdus spp. and Photorhabdus spp. cell suspensions completely prevented egg hatching of M. incognita at 48 hrs exposure time. Bacterial cell suspensions and bacterial toxins equally inhibited egg hatching and immobilized juveniles. Bacterial cell suspensions and toxins of Xenorhabdus spp. and Photorhabdus spp. caused more than 90% immobilization of juveniles. The persistence effectiveness of bacterial cell suspensions and toxins in soil were evaluated up to 7, 14 and 21 days against M. incognita and determined that Xenorhabdus spp. and Photorhabdus spp. were effective in suppressing number of galls, number of females, egg masses and reproduction factors after 7 days of application followed by 14, 21 days of application. The efficacy of bacteria and toxins decreased in the soil over long period of time. These bacteria and their metabolites can be stored in vitro on room temperature up to the period of 5 months. Protective and curative effects of Xenorhabdus spp. and Photorhabdus spp. and their toxins on root-knot nematodes were also studied on nematode development parameter, number of females and reproduction factors. All treatments proved effective as comparedto the control. Protective effect of Xenorhabdus spp. and Photorhabdus spp. and their toxins at standard concentrations were more effective in controlling the number of females and reproduction factor of root knot nematodes than their curative effect. Compatibility and the combined action of bacteria (Xenorhabdus spp. and Photorhabdus spp.) and toxins with bio-products (abamectin, emamectin and azadirachtin) against M. incognita were also evaluated. The results of the study showed that the combined use of bacterial cell suspensions and abamectin significantly reduced the population of M. incognita and have synergistic effect with each other.