אסיף מאגר המחקר החקלאי

Genetic enhancement of nematicide resistance in entomopathogenic nematodes

Year:

1997

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Volume :

7

Co-Authors:

Glazer, I., Department of Nematology, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Salame, L., Department of Nematology, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Segal, D., Dept. Molec. Microbiol. and Biotech., Tel Aviv University, Tel Aviv 69978, Israel

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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 (h2) of resistance to the three nematicides were obtained from analysis of inbred lines derived from the base population. The heritability estimate for Fenamiphos was h2= 0.31, for Oxamyl h2= 0. 71 and for Avermectin h2= 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 entomopathogenic nematodes to certain environmental stresses. The selected lines will be useful bioinsecticides in the context of integrated pest management.

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