Isolates of the Pasteuria penetrans Group from Phytoparasitic Nematodes in Bermudagrass Turf.

A survey was conducted between 1985 and 1989 of isolates of the Pasteuria penetrans group on phytoparasitic nematodes in bermudagrass (Cynodon spp.) turf in southern Florida. Six different isolates of the P. penetrans group were observed from five different species of phytoparasitic nematode hosts. Five of the bacterial isolates were different (P </= 0.01) in sporangium diameter, endospore width, and ratio of sporangium diameter to endospore width. All locations surveyed had one or more isolates present, suggesting that the Pasteuria penetrans group is widespread in its distribution in southern Florida. Three survey sites had high densities of Belonolaimus longicaudatus, with more than 60% of the host population encumbered with a large-spored isolate of Pasteuria (mean sporangium diameter = 6.10 mum). One of these sites was monitored for 16 months during which the proportion of nematodes encumbered with this Pasteuria isolate remained constant. Soil infested with this isolate was not suppressive to Pasteuria-free populations of B. longicaudatus grown on bermudagrass for 6 months after controlled soil inoculation. However, the proportion of spore-encumbered and parasitized B. longicaudatus after 6 months was 73%, which was similar to the 74% level observed at the field site. The uhrastructure of mature sporangia of the large-spored isolates of Pasteuria from B. longicaudatus and Hoplolaimus galeatus is described and compared with ultrastructural descriptions of P. penetrans sensu strictu and P. thornei from the literature. These B. longicaudatus and H. galeatus isolates of Pasteuria appear to be distinct from the known species and may warrant new species status.