DISTRIBUTION AND CHARACTERISTICS OF ROOT-NODULE BACTERIA ISOLATED FROM AUSTRALIAN ACACIA-SPP

Root-nodule bacteria capable of nodulating local acacias were isolated from five climatically diverse and geographically widely separated localities in New South Wales. Strains showed marked geographic localization. Fast-growing isolates, culturally and serologically related to Rhizobium, were obtained from the arid zone but from no other area. Alpine isolates had particularly slow growth rates, with fifty percent taking longer than 10 days to form colonies on yeast mannitol agar. Strains from the rain-forest and coastal health areas had the characteristics of typical Bradyrhizobium. Most of the strains tested had a wide host range, nodulating members of both the Mimosaceae and the Fabaceae, although the extra-slow growing alpine isolates appeared specific for their original host. Isolates varied in their effectiveness with a third of strains failing to give significant weight increases in inoculated plants.