IDENTIFICATION AND BIOLOGICAL-ACTIVITY OF NEWLY ISOLATED HETERORHABDITID POPULATIONS FROM ISRAEL

The present study describes specific identification and characterizati on of the biological activity of entomopathogenic nematodes which were isolated from soil samples in a recent survey of the arid '' Negev '' region of Israel. Morphological examination indicated that the nemato de populations designated IS1, IS2 and IS3 represent strains of Hetero rhabditis bacteriophora Poinar. Whereas IS4 is considered a strain of H. megidis Poinar, Jackson & Klein. The identification for IS-3 and IS 4 isolates was confirmed by analysis of total DNA on restriction fragm ent length differences of repetitive sequences, while the IS2 and IS3 isolates showed banding pattern different from that of H. bacteriophor a. In infectivity assays the IS4 strain of H. bacteriophora was found to be the most pathogenic of the four new population and the HP 88 str ain of H. bacteriophora against the lepidopteran species Galleria mell onella, Earias insulana, Spodoptera littoralis. IS, infectivity to the lepidopteran strain was equivalent to that of the steinernematid Stei nernema carpocapsae All strain. The superior infectivity of the IS4 wa s also demonstrated against the scarab Maladera matrida. Viability of the H. bacteriophora HP 88 infective juveniles was reduced to 20 % whe n exposed to 37-degrees-C for 3 h. The level of survival of all other heterorhabditids strains was 3-4.5 fold higher than the HP 88 strain. The viability of S. carpocapsae All strain was not affected by the sam e heat treatment. Exposure to low relative humidity conditions (3 h at 50-60 % RH) resulted in 55-85 % reduction in most of the various nema tode populations. Relatively high tolerance to the desiccation conditi ons was recorded with the IS1 and IS3 heterorhabditid isolates.