A Below Ground Chemical Fight for Phosphate and Habitat - Interactions of Camelina sativa (L.) Crantz with Microorganisms

Abstract BACKGROUND and AIMS Glucosinolates and isothiocyanates of young Camelina sativa (L.) Crantz can eliminate microbial species in the soil. It was aimed to demonstrate that only isothiocyanate insensitive microorganisms with phosphate solubilizing activity can be successfully used to improve the plant´s phosphate supply. METHODS We performed rhizotron growth studies and 33P–Imaging to study the uptake of phosphate solubilized from 33P-apatite by inoculated plants and determined the phosphate solubilization capacities of microorganisms by inductively coupled plasma mass spectrometry. Secondary metabolites of Camelina sativa and of the soil fungus Penicillium aurantiogriseum were analyzed by HPLC-MS/MS. Microorganisms and plant seedlings were cultured for growth inhibition studies. Phospholipid fatty acids in soil samples were investigated by gas chromatography and the data analyzed by clustering and principal component analysis. RESULTS 1. The inoculants Trichoderma viride and Pseudomonas laurentiana did not improve the phosphate uptake of Camelina sativa and Abutilon theophrasti. 2. The intrinsic soil microorganisms, including Penicillium aurantiogriseum, the inoculants and the assemblies of root colonizing microorganisms are able to solubilize phosphate from apatite and compete for phosphate. 3. Camelina´s glucosinolates and derived isothiocyanates and, as well secondary metabolites released by P. aurantiogriseum, particularly cyclo-(L-Leu-L-Pro), have the capacity to suppress plant and fungal growth and to destroy a phosphate solubilizing bacterial consortium that colonizes Camelina roots. 4. Loss of young Camelina´s key secondary metabolites, the glucosinolates, is of advantage for fungi, as verified by a green manure experiment. CONCLUSION The results underline functions of secondary metabolites when organisms are under competive conditions for phosphate uptake.