Enumeration of Bradyrhizobium japonicum in soil subjected to high temperature: Comparison of plate count, most probable number and fluorescent antibody techniques

The survival of BradyrMzobium japonicum strains in autoclaved and non-autoclaved soil at various temperatures for up to 18 days was determined by plate count, plant infectivity-most probable number (MPN) and modified fluorescent antibody (FA) techniques. The high-temperature tolerant strains studied were BR587, NC1005 and NC1033, and the high-temperature intolerant strains studied were NCI028, 3Ilb24 and 311b123. Each strain was exposed individually in a sandy loam soil at 28, 33 or 37°C under humidity controlled conditions. Those strains reported to be tolerant to elevated temperature in pure culture decreased by