11 / 02 / 2008

Tournai-acceuil

Le BIO

unisem
the organic way

unisem
goes organic !

culture biologique

horticulture

Le phosphonate de potassium, sel potassique de l'acide phosphoreux (phosphonique), considéré par les législations européennes comme un engrais phospho-potassique foliaire et, à ce titre, libre à la vente, mais doté d'un pouvoir stimulant des défenses des plantes. (PK2 ▲ )

Étudié, surtout en viticulture, d'abord sur le mildiou (Plasmopara viticola), depuis 1993, puis sur l'oïdium (Uncinula necator).

En Belgique en pomme de terre :

Phosphite de potassium + Tallate de cuivre :  VETAB INFO février 2007

( CRA-W +32 (0) 61 23 10 10 Brice Dupuis,  dupuis@cra.wallonie.be )

carah

VETAB

fiches pratiques en agriculture biologique

ITAB

journée fruits légumes biologiques

• Analyse des systèmes agricoles sous l’angle de leur durabilité économique, environnementale et sociale. Recherches sur la filière de production de la pomme de terre - http://www.cra.wallonie.be/craw/units/d82/pdf/CRA-W_ra03-04_d82_fr.pdf

• Ilangovan Ramasamy, Ph.D - AgriInfoTech.  A Brief Note: Potassium phosphite against Phytophthora - http://www.agriinfotech.com/htmls/PDF-Files/GENERAL/BRIEF%20NOTE%20ON%20THE%20EFFECT%20OF%20POTASSIUM%20PHOSPHONATE%20ON%20PHYTOP.pdf

• Coffey, M. D., and Ouimette, D. G. 1989. Phosphonates: Antifungal compounds against oomycetes. Pages 107-129 in: Nitrogen, Phosphorous, and Sulfur Utilization by Fungi. L. Boddy, R. Marchant, and D.J. Read, eds. Cambridge University Press, Cambridge, England.

• The effect of foliar application of phosphonate formulations on the susceptibility of potato tubers to late blight

Louise R Cooke 1 2 *, George Little 1

Applied Plant Science Division, Department of Agriculture and Rural Development, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK

Department of Applied Plant Science, The Queen's University of Belfast, Agriculture and Food Science Centre, Newforge Lane, Belfast BT9 5PX, UK

email: Louise R Cooke ( Louise.Cooke@dardni.gov.uk )

Correspondence to Louise R Cooke, Applied Plant Science Division, Department of Agriculture and Rural Development, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK

Abstract

Foliar sprays of potato plants with phosphonic acid (partially neutralised with potassium hydroxide to pH 6.4) substantially reduced infection of the tubers by Phytophthora infestans, the cause of late blight, in glasshouse and field experiments over a 4-year period. Healthy tubers of blight-susceptible cultivars removed from treated plants and artificially inoculated by spraying with sporangial/zoospore suspensions of P infestans did not develop disease symptoms, demonstrating that the phosphonate applications had directly reduced the susceptibility of tubers to infection, probably as a result of translocation into tuber tissue. In contrast, foliar application of fosetyl-aluminium did not significantly reduce tuber blight development following inoculation. Five to six sprays of partially neutralised phosphonic acid (2 kg ha-1) applied at 10-14 day intervals resulted in the least tuber infection, but such a treatment regime may not be economic. In trials where the effect of timing and rate of application of 2-4 kg phosphonic acid ha-1 was examined, a single treatment of 4 kg ha-1 applied mid- or late-season proved the most effective. A spray programme in which one or two applications of phosphonic acid are combined with use of a non-systemic or systemic fungicide to enhance foliar protection offers the possibility of controlling both foliage and tuber blight and could have a major impact in reducing overwinter survival of P infestans in tubers.

• Defence responses induced by potassium phosphonate in Phytophthora palmivora-challenged Arabidopsis thaRosalie Daniel and David Guest danielr@agric.usyd.edu.au Faculty of Agriculture, Food and Natural Resources, John Woolley Building A20, The University of Sydney, NSW 2006, Australia

Abstract

Potassium phosphonate, a systemically translocated chemical used to protect plants against oomycete pathogens, induces rapid, localised defence responses in normally susceptible plants that are similar to those observed in an incompatible interaction. We demonstrated that in phosphonate-treated Arabidopsis thaliana seedlings inoculated with zoospores of Phytophthora palmivora, challenged cells respond with a rapid increase in cytoplasmic activity, the development of cytoplasmic aggregates, the release of superoxide, localised cell death and enhanced accumulation of phenolic materials around the infected cell. Pathogen development is severely restricted, and hyphae that develop in phosphonate treated seedlings appear distorted and sporangial production is inhibited. These rapid host responses are absent or muted in untreated inoculated seedlings, and the pathogen rapidly colonises seedling tissues, developing abundant sporangia within 24 h of inoculation. The presence of Mn(III)-desferal, a treatment that quenches superoxide release, abolishes hypersensitive cell death and facilitates pathogen development in phosphonate-treated plants, indicating that pathogen inhibition is a consequence of superoxide release rather than direct inhibition due to phosphonate.