VARIATION IN PATHOGENICITY OF RECOMBINATIONS OF HETERORHABDITIS AND XENORHABDUS-LUMINESCENS STRAINS

Xenorhabdus luminescens isolates were exchanged between four insect pa thogenic nematode strains: two different Heterorhabditis isolates from the Netherlands and two different Heterorhabditis bacteriophora isola tes. Of the sixteen possible combinations three combinations, of Dutch nematodes with bacteria of H. bacteriophora, were not able to grow an d multiply. Of the thirteen combinations that could be propagated the four combinations of H. bacteriophora nematodes with bacteria from the Dutch nematodes were not pathogenic. When waxmoth larvae were injecte d with bacteria, the four non-pathogenic combinations were able to pen etrate and multiply in these larvae. This showed that the lack of path ogenicity of these four combinations was due to the absence of bacteri a. Both H. bacteriophora strains penetrated insect larvae in lower num bers than both Dutch Heterorhabditis strains, independent what bacteri um they were carrying.