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Differences in Immune Defense Evasion of Selected Inbred Lines of Heterorhabditis Bacteriophora in Two White Grub Species
Department of Entomology, Ohio State University, 1680 Madison Ave, Wooster, OH 44691, USA
Embrapa Trigo, Passo Fundo, Rio Grande do Sul 99001-970, Brazil
Department of Plant Pathology, University of Georgia, Athens, GA 30605, USA
* Author to whom correspondence should be addressed.
Received: 7 February 2012; in revised form: 1 March 2012 / Accepted: 14 March 2012 / Published: 23 March 2012
Abstract: We determined virulence of seven Heterorhabditis bacteriophora strain GPS11 inbred lines possessing superior infective juvenile longevity, and heat and ultra violet radiation tolerance against white grubs Popillia japonica and Cyclocephala borealis. At 1 and 2 weeks after treatment, inbred line A2 was significantly more virulent towards P. japonica compared to the parent strain GPS11 and inbred lines A7, A8, A12 and A21; and line A2 caused significantly higher C. borealis mortality than lines A6 and A12. Penetration, encapsulation and survival of two inbred lines, A2 and A12, that showed the highest and lowest virulence against both grub species were then assessed. There were no differences between the two lines for the total number of nematodes penetrated in either P. japonica or C. borealis within the first 24 h, but a significantly higher percentage of penetrated nematodes were alive in line A2 compared to the line A12 in both grub species. P. japonica immune response over time to hemocoel-injected nematodes of A2, A12 and the parent strain was further investigated. While all injected nematodes were encapsulated at 6 h post injection, non-encapsulated living nematodes were detected at 12 and 24 h post injection, showing the breakage out of encapsulation. A higher percentage of non-encapsulated living nematodes and a lower percentage of dead nematodes were found in line A2 as compared to the line A12 after 12 h post injection. These data suggest that virulence differences in the studied H. bacteriophora inbred lines are not due to differences in nematode penetration or recognition by the grub immune system, but are related to the ability of the infective juveniles to break out of encapsulation.
Keywords: entomopathogenic nematodes; Heterorhabditis bacteriophora; inbred lines; white grubs; immune defense
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An, R.; Voss, M.; Jagdale, G.B.; Grewal, P.S. Differences in Immune Defense Evasion of Selected Inbred Lines of Heterorhabditis Bacteriophora in Two White Grub Species. Insects 2012, 3, 378-389.
An R, Voss M, Jagdale GB, Grewal PS. Differences in Immune Defense Evasion of Selected Inbred Lines of Heterorhabditis Bacteriophora in Two White Grub Species. Insects. 2012; 3(2):378-389.
An, Ruisheng; Voss, Marcio; Jagdale, Ganpati B.; Grewal, Parwinder S. 2012. "Differences in Immune Defense Evasion of Selected Inbred Lines of Heterorhabditis Bacteriophora in Two White Grub Species." Insects 3, no. 2: 378-389.