Isolation and characterisation of plant growth promoting Rhizobacteria (PGPR) endemic to Western Australina soils

Rhizosphere soil was collected from under crops of wheat and peas and from stands of native Australian vegetation in order to isolate novel plant growth promoting rhizobacteria (PGPR) endemic to Western Australian soils. The PGPR were isolated on the basis of either their ability to produce indole-3-acetic acid (IAA) or 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, which are common PGPR traits. Selected isolates were screened for plant growth promotion using growth pouch assays and field trials. The isolates were further screened for other PGPR traits such as siderophore production, antifungal activity and phosphorus solubilisation. Several isolates showing strong phosphorus solubilisation in vitro were tested in the glasshouse on wheat (Triticum aestivum c. v. Wyalkatchem) for their ability to solubilise calcium phosphates and hence improve plant growth using a soil that was naturally phosphorus deficient. A number of isolates improved plant biomass and yields and/or protein, phosphorus and nutrient contents of the grain. Two isolates have been selected for further glasshouse trials: a Burkholderia species (isolated from native vegetation) that improved average grain weights and protein and nutrient contents but not total yield and a Pseudomonas species (isolated from wheat) that improved yields. The glasshouse experiment will determine the response of these two species to different rates of phosphorus application and hence ascertain if phosphorus solubilisation is the mechanism of action of plant growth promotion.