I. Glazer et al., GENETIC ENHANCEMENT OF NEMATICIDE RESISTANCE IN ENTOMOPATHOGENIC NEMATODES, Biocontrol science and technology, 7(4), 1997, pp. 499-512
Entomopathogenic nematodes are highly effective bioinsecticides. Their
efficacy may be reduced due to the various pesticides they encounter
in the soil. These include insecticides as well as nematicides used ag
ainst plant-parasitic nematodes. The purpose of this study was to exam
ine the feasibility of genetic selection as means of enhancing resista
nce of the entomopathogenic nematode Heterorhabditis bacteriophora str
ain HP88 to the nematicides: Fenamiphos (an organophosphate), Oxamyl (
a carbamate) and Avermectin (a biological product). Estimates of herit
ability (h(2)) of resistance to the three nematicides were obtained fr
om analysis of inbred lines derived from the base population. The heri
tability estimate for Fenamiphos was h(2) = 0.31, for Oxamyl h(2) = 0.
71 and for Avermectin h(2) = 0.46. Five rounds of selection were perfo
rmed. Thereafter, each line was divided into two: for one subline sele
ction continued for six additional rounds. The other subline was reare
d without selection for the six additional rounds. After the eleventh
round, resistance to the nematicides was examined as were several trai
ts relevant to biocontrol efficacy including virulence, heat tolerance
and reproduction potential. Selection resulted in an 8-9-fold increas
e in resistance to Fenamiphos and Avermectin and a 70-fold increase in
resistance to Oxamyl. The enhanced resistance Oxamyl and Avermectin,
and to a lesser extent to Fenamiphos, was stable and continued after s
election was relaxed. No deterioration in traits relevant to biocontro
l efficacy was observed in the selected lines as compared with the bas
e population. The selected lines displayed enhanced cross-resistance t
owards some, but not all, of the nematicides tested. These results dem
onstrate that genetic selection can be used to enhance resistance of e
ntomopathogenic nematodes to certain environmental stresses. The selec
ted lines will be useful bioinsecticides in the context of integrated
pest management.