Estimation of Pasteuria penetrans Spore Load and effect of Selective Elimination of Soil Fungi and Bacteria on the Efficacy of P. penetrans in the Suppression of Meloidogyne javanica in Soil

Based on a laboratory bioassay, a statistical model was developed for the estimation of Pasteuria penetrans spores in field soil (clay- 7.6%, silt- 2.0%, sand- 90.4%, pH- 7.0, organic matter- 0.77%). The role of P. penetrans in the suppression of Meloidogyne javanica in naturally infested field soil was studied in a green-house test. The soil was steam-sterilized or treated with Formalin or fungicides Ridomil and/or Bavistin for complete or selective elimination of native soil biota. Ridomil alone did not adversely affect the nematode root infection and reproduction. P. penetrans alone caused 87.5% infection endospores and reduced egg production by about 10 times. Native fungal and bacteria promoted attachment of P. penetrans endospores but inhibited parasitisation of nematode females by P. penetrans in untreated soil.