Characterisation of pasteuria isolated from Heterodera cajani using morphology, pathology and serology of endospores

Pasteuria spp. are potentially useful natural parasites of nematodes. An isolate of Pasteuria, recovered from the pigeonpea cyst nematode, Heterodera cajani, was characterised using host range, spore morphometrics, and serology. The spores of this isolate had a mean diameter of 2.36 mu m, the smallest described so far on nematodes. Based on spore encumberance on nematode cuticle, Globodera rostochiensis, G. pallida, Heterodera glycines, H. trifolii, H. schachtii, and Rotylenchulus reniformis were hosts and H. carotae, H. galeopsidis, Meloidogyne arenaria, M. incognita, M. javanica, M. graminicola, M. oryzae, M. triticoryzae, M. sasseri, M. graminis, and M. naasi were non hosts. Spore attachment on the nematode body was random except on H. trifolii, where the spores selectively attached to the head region. Marked heterogeneity in sport size and level of spore attachment within populations of nematode species was observed. Variation in antigens present on the spore surface was confirmed by differential recognition of spores by monoclonal and polyclonal antibodies and Western blot analysis. The parameters important in characterising species of Pasteuria are discussed in the light of the data reported. The results suggest that host range and spore morphometrics are not adequate for the characterisation of species.