Effect of Gamma Irradiation on Viability, Pathogenicity, Reproductivity of Heterorhabditis bacteriophora and H. indica and detection of DNA Damage

Abstract

Entomopathogenic nematodes (EPNs) are a promising alternative method for insect pest control. The idea of the work is to investigate the effect of gamma irradiation on EPNs pathogenicity under laboratory conditions aiming to enhance their lethal effect against insect pests. Heterorhabditis bacteriophora (Hb) as well as H. indica (Hi) were irradiated directly in nematode suspension and indirectly within the insect cadavers by gamma irradiation dosages of 0, 100, 250, 500, 750 and 1000 Gy.The mortality percentage of nematodes were recorded, the extracted nematodes from the irradiated insect hosts were used to investigate their pathogenicity and reproductivity against Galleria mellonella larvae. The damage of DNA was analyzed using the comet assay and the LC50 of the two nematode species was recorded. The data demonstrated that, the low dosage (100 Gy) enhanced the pathogenicity of EPNs and didn't affect the initial populations (Pi), the final population of emerged IJs (Pf) and the rate of reproduction (Rr%). Moreover, H. bacteriophora was more tolerant to gamma irradiation than H. indica which recorded more DNA damage %, DNA in tail, tail length, tail moment and olive tail moment in the all different irradiated dosages. In conclusion, low dosages of gamma irradiation can be used to enhance the pathogenicity and reproductivity of entomopathogenic nematodes in order to use as a biocontrol agent.