Phosphate solubilisation and gluconic acid production by endophytic bacterial strains and ability to promote plant growth in oil seed rape (Brassica napus)

Citation:
Otieno N, Culhane J, Germaine K, Brazil D, Ryan D, Dowling D. Phosphate solubilisation and gluconic acid production by endophytic bacterial strains and ability to promote plant growth in oil seed rape (Brassica napus). 18-21 May 2012, Aldemar Hotel, Rhodes, Greece: New Phytologist Organisation; 2012.

Abstract:

Several studies have shown that the release of low molecular weight organic acids is
a major mechanism for solubilising insoluble phosphate by phosphate solubilising
bacteria (PSB). The production of gluconic acid during inorganic phosphate
solubilisation in conjunction with liberation of phosphate and the influence on plant
growth as a function of phosphate solubilisation by endophytic strains was analysed.
Solubilisation of Ca3(PO4)2 in National Botanical Research Institute’s Phosphate
(NBRIP) growth medium varied among the endophytes with P-liberated ranging from
1109.33 μg/ml to 67.3 μg/ml. In all cases, the final supernatant had a significant pH
decrease and this had a direct relation to P-liberated. High Performance Liquid
Chromatography (HPLC) analysis of the culture filtrate to quantify gluconic acid
produced by the strains ranged from 33.21±2.34 mg/ml to 2.2 ±0.18 mg/ml. The
results suggest that acidification was the main strategy for solubilising phosphate. In
this study, a clear relationship was observed between supernatant acidification and
P solubilisation from Ca3(PO4)2. However, no significant difference was observed for
key growth parameters in oil seed rape between treatments. The result of this study
indicates in planta expression of P solubilisation traits may be more complex than
those in vitro studies.

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