|Shapiro Ilan, David|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2009
Publication Date: 10/22/2009
Citation: Shapiro Ilan, D.I., Mbata, G.N., Nguyen, K.B. 2009. Characterization of biocontrol traits in the entomopathogenic nematode Heterorhabditis georgiana (Kesah strain), and phylogenetic analysis of the nematode's symbiotic bacteria. Biological Control. 51:377-387. Interpretive Summary: Entomopathogenic nematodes are naturally occurring small round worms that are used as environmentally friendly bio-insecticides. When a new species (kind) of entomopathogenic nematode is discovered it is important to determine its potential in terms of pest control ability. Our objective was to estimate the pest control potential of the recently discovered entomopathogenic nematode species named Heterorhabditis georgiana (Kesha strain). In laboratory experiments, we compared the new nematode to various other entomopathogenic nematode species for the ability to kill several insect pests, ability to withstand adverse levels of heat, desiccation, cold, and low oxygen levels, and ability to detect and find an insect. Heterorhabditis georgiana expressed low or intermediate capabilities in all traits tested indicating a relatively low pest control potential. Nevertheless, some novel observations resulted from comparisons among other nematode species tested. For example, another recently discovered nematode species, H. floridensis, exhibited relatively high virulence to citrus weevils. And, in terms of cold tolerance, some nematodes showed the ability to kill insect pests at low temperatures of 10 oC, whereas other nematodes were able to penetrate insects at 10 oC and remain in the insect (without killing it) until more suitable temperatures resumed (25 oC), at which time the insect died.
Technical Abstract: Our objective was to estimate the biocontrol potential of the recently discovered entomopathogenic nematode species, Heterorhabditis georgiana (Kesha strain). Virulence and environmental tolerance were tested among several nematode species. Heterorhabditis georgiana expressed low or intermediate capabilities in all virulence and environmental tolerance assays thus indicating a relatively low biocontrol potential. Nevertheless, some novel observations resulted from comparisons among other species tested. In virulence assays, H. indica and S. riobrave exhibited the highest virulence to D. abbreviatus and P. interpunctella, yet the previously untested H. floridensis also exhibited relatively high virulence to D. abbreviatus, and the virulence of H. indica to P. interpunctella was slightly higher than that of S. riobrave. Relative to the other species tested, at 10 oC S. feltiae exhibited superior ability to cause mortality in G. mellonella (100%) yet, H. bacteriophora and H. georgiana exhibited the ability to produce attenuated infections at 10 oC, i.e., the infections resumed and produced mortality at 25 oC. In contrast, H. indica did not show an ability to cause attenuated infections.