Endospores of a Pasteuria sp. were observed on Heterodera glycines second-stage juveniles and males recovered from soil in microplots in which nematode populations had been declining for several years. Conventional scanning electron microscopy was used to observe and measure endospores on second-stage juveniles (J2) of both a race 3 and a race 4 population. Endospores were elipsoidal; those attached to J2 of race 3 measured (X) 4.2 x 3.7 mum with a height of 2.0 mum, and those on race 4 were 4.3 x 3.7 mum with a height of 2.3 mum. Measurements taken under light microscopy indicated that endospores attached to J2 of race 3 were 5.0 x 4.8 mum with a height of 2.2 mum. The velutinous exosporium of the H. glycines-infecting P. nishizawae from Japan was not visible in the Illinois isolate. Differences in endospore morphology and the apparent inability of the Illinois isolate to complete its life cycle in females indicate that the Japanese and Illinois isolates are distinct species of Pasteuria.
Keywords: Heterodera glycines; Pasteuria sp.; biological control; nematode; soybean cyst nematode.