Abstract
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 against plant - parasitic nematodes . The purpose of this study was to examine the feasibility of genetic selection as a means of enhancing resistance of the entomopathogenic nematode Heterorhabditis bacteriophora strain HP88 to the nematicides: Fenamiphos (an organophosphate) , Oxamyl (a carbamate) and Avermectin (a biological product) . Estimates of heritability ( h 2) of resistance to the three nematicides were obtained from analysis of inbred lines derived from the base population . The heritability 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 performed . Thereafter , each line was divided into two: for one subline selection continued for six additional rounds . The other subline was reared without selection for the six additional rounds . After the eleventh round , resistance to the nematicides was examined as were several traits relevant to biocontrol efficacy including virulence , heat tolerance and reproduction potential . Selection resulted in an 8 - 9 - fold increase 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 selection was relaxed . No deterioration in traits relevant to biocontrol efficacy was observed in the selected lines as compared with the base population . The selected lines displayed enhanced cross - resistance towards some , but not all , of the nematicides tested . These results demonstrate that genetic selection can be used to enhance resistance of entomopatho genic nematodes to certain environmental stresses . The selected lines will be useful bioinsecti cides in the context of integrated pest management .
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