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Phosphorus Use efficiency Bioassay in planta
M.E. Saint-Macary(1), X. Salducci(2), F. Giraud(3)
Abstract Phosphorus is often the most limiting nutrient in agro-ecosystems because the main forms of Phosphorus are immobilized in soil. Numerous developed plant Biostimulant products aim at helping to face the limitation of Phosphorus in soil by using bio-effectors (microorganisms and natural active compounds) to increase the phosphorus-use efficiency of major crops. Staphyt in collaboration with Celesta-lab, has developed an in planta bioassay to assess the putative effect of new bio-effectors to facilitate availability or assimilation of Phosphorus in controlled conditions.
This bioassay is used as a screening test to search new effective solutions (active substances and/or micro-organism strains) or to validate the efficacy of the newly developed products.
Conclusions
Background
The developed bioassay is an adaptation of the Phosphorus bioavailability test, according to Standford-De Ment method.
The effectiveness of the biostimulant product to improve the bioavailability of phosphorus for the plant is evaluated by following the phosphorus uptake from a natural phosphate (tri-calcium phosphate) in a phosphorus deficient soil with or without the test item, compared to a highly soluble mineral phosphate fertilizer (pure mono-calcium phosphate) added to the culture system.
We have developed an efficient in planta bioassay to evaluate fertilizers or biostimulant products helping the Phosphorus use efficiency, in controlled conditions using the most agricultural P form (P2O5).
Results
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Soil (S) S + insoluble P S + insoluble P +Biostim
S + soluble P
Exp
ort
ed
P (
mg
/po
t)
Plant Phosphorus bioavailability from soil
Tri-calcium P (negative check)
Tri-calcium P + test item
Mono-calcium P (positive check)
P exports from the shoots part of ryegrass after 30 days of plant cultivation in controlled conditions (n = 5). Soil (S) = P deficient soil, S + insoluble P (negative check) = P deficient soil + tricalcium phosphate (100 ppm), S + insoluble P + Biostim = P deficient soil + tricalcium phosphate (100 ppm) + microorganism strain, S + soluble P (positive check) = P deficient soil + monocalcium phosphate (100 ppm) .
(1) Staphyt, La Paluzette, Route des Mas 34590 Marsillargues, FRANCE ([email protected]) (2) Celesta Lab, 154 Rue Georges Guynemer, 34130 Mauguio, FRANCE ([email protected]) (3) Staphyt, Avenue François Magendie, Site Montesquieu, 33650 MARTILLAC, FRANCE ([email protected])
Our system provide key results about the P exportation from the soil to the ryegrass plant. Other crops are currently in development.
A new system using phytate as P source is also available specifically for Phytase positive microorganisms.
Outlook
Test Development
This is an in planta test conducted in controlled conditions (temperature, humidity and light) using the perennial ryegrass as a plant model.
Specific conditions are used in order to : independently control the conditions of germination; retain moisture and allow favorable aeration levels of the substrate for germination and plant growth; and evaluate products mixed with several types of substrates (sand, earth, ...).
Support and Acknowledgement We are grateful to C. Profizi (Soufflet Biotechnologies) who helped in the method development.
