LIGHT AND ELECTRON-MICROSCOPIC STUDIES OF THE LIFE-CYCLE AND DEVELOPMENTAL STAGES OF A PASTEURIA ISOLATE PARASITIZING THE PEA CYST-NEMATODE, HETERODERA-GOETTINGIANA

In a Pasteuria isolate (HGP) found in the pea cyst nematode, Heteroder a goettingiana, at Munster, Germany, the mode of infection, the develo pmental cycle and the morphology and ultrastructure of the development al stages up to the immature sporangia are similar to those found in t he three nematode-parasitic Pasteuria species previously described. Th e exclusive presence of all parasitic stages in the second-stage juven iles of H. goettingiana separates HGP from P. penetrans and P. nishiza wae, which complete their life cycles in the females of Meloidogyne an d Heterodera, respectively and do not infect migrating juveniles. HGP is also different from P. thornei, which parasitizes both juvenile and adult stages of Pratylenchus. The ultrastructural, morphological and morphometric features, which are different from those previously descr ibed for other species of Pasteuria, together with the distinction in host range and developmental stage specificity suggest that HGP should be assigned a new species within the genus Pasteuria.