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Mukuka J.,University of Kiel | Mukuka J.,Zambia Agricultural Research Institute ZARI | Strauch O.,University of Kiel | Zainab M.H.A.,University of Aleppo | Enters R.-U.,University of Kiel
Russian Journal of Nematology | Year: 2010

The effect of stress exposure on the infectivity of heat and desiccation tolerant hybrid strains of the entomopathogenic nematode Heterorhabditis bacteriophora was assessed against last instars of Galleria mellonella. Nematode dauer juveniles (DJs) were exposed to desiccation stress at a water activity (aw-value) of 0.85 for 24 h or a temperature treatment at 40°C or 0°C for 24 h prior to inoculation of 5 DJs per insect. Hybrid strains resulting from crosses of the three very best heat or desiccation tolerant strains and crosses of heat with desiccation tolerant strains were compared with a commercial strain of H. bacteriophora. Exposure to desiccation stress caused significant reduction of the infectivity in all strains not surpassing 25% mortality, except one that was not affected and achieved 37.5% mortality. Infectivity of untreated DJs of desiccation tolerant hybrids differed significantly with a mean infectivity of 54%, ranging from 33.8% to 89.6%. The mean mortality of heat tolerant hybrids was significantly higher (78.2%). The commercial and two other hybrids were not affected by the heat treatment. The lowest mortality after the low temperature treatment was recorded for the commercial strain. The reduction in infectivity after cold temperature treatment was not much different from the effect recorded after heat treatment and results were not consistent between strains. Consequently, we conclude that the infectivity of heat tolerant strains is not necessarily affected by low temperature stress. Monitoring of beneficial traits like infectivity is essential during attempts to improve genetically other traits by crossing tolerant strains or selective breeding. Source

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