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Plant growth-promoting bacteria from Western Australian soils

Swift, Rebecca Gaye (2016) Plant growth-promoting bacteria from Western Australian soils. PhD thesis, Murdoch University.

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Harnessing the abilities of soil microbes to improve plant health and productivity may be an important factor in obtaining food security for the future. In this study, 179 potential plant growth-promoting bacteria (PGPB) were isolated from the rhizosphere of five types of plants from three Western Australian soils. On the basis of in vitro plant growth promotion assays, seven isolates were selected for testing in field trials in Western Australia. Two of the PGPB, Burkholderia caledonica NCH45 and Enterobacter soli ANMK1, improved the yield of wheat by 23% and 9% respectively. The isolate, Pseudomonas granadensis PMK4, improved nodulation when co-inoculated with rhizobia on peas by up to 71% and grain yields by 35%. P. granadensis PMK4 was shown to inhabit the nodules of the field grown peas using strain specific primers developed in this study from the 16S-23S rRNA ITS1 region of this isolate. P. granadensis PMK4 was also tested in field trials on Christmas Island on several legume species at three different fertilizer levels (nil, low and high). Significant increases in nodulation and/or plant yields were observed for soybean and mungbean co-inoculated with PMK4 and rhizobia at a low level of applied fertilizer compared with rhizobia only controls. Co-inoculation with PMK4 also significantly increased the copper and phosphorus concentration in the shoots of lablab and soybean at the nil (lablab) and low (lablab and soybean) fertilizer levels. Glasshouse trials using a full phosphorus response curve demonstrated that phosphorus solubilisation is not the mechanism of action by NCH45 and PMK4 in wheat. However, growth pouch assays using the auxin transport inhibitor, 2,3,5-triiodobenzoic acid, indicate that production of indole-3-acetic acid may be at least partly responsible for increasing wheat seedling root lengths. These results support the further testing of the three promising isolates in field trials to determine optimal conditions for improving plant productivity.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): McComb, Jen, Hardy, Giles and Brau, Lambert
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