Desiccation tolerance among different isolates of the entomopathogenic nematodeSteinernema feltiae (Filipjev)

Abstract: Poor storage capacity is a major constraint limiting further expansion of the use ofentomopathogenic nematodes. In order to prolong shelf life, a quiescent state of the dauerjuveniles (DJs) should be induced. This can be attained by means of desiccation of DJs. In thisstudy, 24 natural isolations of Steinernema feltiae were exposed to desiccation stress in non-ionicpolyethylene glycol 600. The dehydrating conditions were measured as water activity, aw-value.Non-adapted and adapted DJs were tested separately under a series of dehydrating conditions.The mean tolerated aw-value (MW50) ranged from 0.85 for the isolate NEP1 to 0.95 for FIN1,ISR5 and PAL4 when not adapted to desiccation stress and from MW50 of 0.822 for CR1 to 0.98for ISR6 when adapted to the stress conditions. CR1 tolerated the lowest desiccation stress at anaw-value for the most tolerant 10% of the population (MW10) at 0.65 when DJs had been adaptedto stress. No significant differences were recorded between all isolates in non-adapted DJspopulations MW10 was compared. No correlation between tolerance under non-adapted andadapted conditions were found. Most tolerant isolates will now be used for cross-breeding andsubsequent genetic selection to enhance desiccation tolerance.