BIOLOGICAL CHARACTERISTICS OF THE ENTOMOPATHOGENIC NEMATODE HETERORHABDITIS SP IS-5 - A HEAT TOLERANT ISOLATE FROM ISRAEL

Entomopathogenic nematode isolate (IS-5), from under the canopy of fru it trees in the arid ''Negev'' region of Israel was found to be highly tolerant to temperatures above 30 degrees C. Morphological measuremen ts did not distinguish this isolate from Heterorhabiditis bacteriophor a Poinar, 1976. However, DNA extracted from four different genotypes ( Heterorhabditis sp. IS-5, HP88 and IS-3 and H. megidis HSH2) amplified with six random primers yielded products from which it was calculated that the similarity between IS-5 and HP88 was 20%, between IS-3 and H P88 85% and between IS-3 and H. megidis 15.6%. Two hours at 37 degrees C killed 79% HP88 infective juveniles but only 18% IS-5. Eight hours at 37 degrees C killed 87% of HP88 but only 28% of IS-5. One hour at 4 0 degrees C killed all infective juveniles of the HP88 isolate but onl y 26% of IS-5. Heat shock treatment for 2 h at 37 degrees C before exp osure to 40 degrees C enhanced the survival of IS-5 juveniles to 43% a s compared with non heat-shocked control. At 25 degrees C IS-5 caused 100% mortality of Galleria melioneila larvae after 36 h and HP88 after 48 h. At 30 degrees C IS-5 caused 100% mortality in 24 h. The average number of nematodes in cadavers exposed to IS-5 and HP88 for 48 h ran ged from 15 to 16.3 and 7.3 to 10.8, respectively. At 25 degrees C bot h these heterorhabditid isolates produced an average of 90,000 infecti ve juveniles per cadaver. At 30 degrees C and 33 degrees C yields of I S-5 increased by 10% but those of HP88 reduced by 90%. At each tempera ture IS-5 juveniles emerged 2-3 days earlier than HP88.