Light and electron microscopical studies of the life cycle and developmental stages of a Pasteuria isolate parasitizing the pea cyst nematode, Heterodera goettingiana

Swn.mary-ln a Pasteun'a isolate (HGP) found in the pea cyst nematode, Heterodera goellingiana, at Munster, Germany, the mode of infection, the developmental cycle and the morphology and u]trastructure of the developmental stages up to the immature sporangia are similar to those found in the three nematode-parasitic Pasleuria species previously described. The exclusive presence of all parasitic stages in the second-stage juveniles of H. goellingiana separates HGP from P. pene/rans and P. nishizawae, which complete their lite cycles in the females of Meloidogyne and He/erodera, respectively and do not infect migrating juveniles. HGP is also different from P. /homez; which parasitizes both juvenile and adult stages of Pra/yleruhus. The ultrastruetural, morphological and morphometric featmes, which are different from those previously described for other species of Pasteun'a, together with the clistinction in host range and developmental stage specificity suggest that HGP should be assigned a new species within the genus Pas/euria.