CLONING OF THE RDNA REPEAT UNIT FROM A BRITISH ENTOMOPATHOGENIC NEMATODE (STEINERNEMATIDAE) AND ITS POTENTIAL FOR SPECIES IDENTIFICATION

The entire ribosomal DNA repeat unit of a steinernematid species (Nash es isolate) was cloned as three separate EcoR I fragments in the plasm id pUC18. An equimolar cocktail of these three clones was used to iden tify Steinernema species on Southern blots as each species displays it s own unique restriction fragment length polymorphisms. The clones als o identified two new species isolated in a soil survey of coastal regi ons of Britain. One of the clones (pSn4.0) can detect length heterogen eities in the rDNA repeat unit of various isolates of some of the spec ies, particularly the most common in the United Kingdom, S. feltiae. T hese differences in the rDNA repeat unit length remained constant over several years for one isolate of S. feltiae, but were different for e ach of the geographical isolates studied to date.