SYSTEMIC IMMUNITY AGAINST SOIL BORNE PHYTOPHTHORA AND CONTROL OF INK DISEASE OF CHESTNUT BY FOLIAR SPRAY OF POTASSIUM PHOSPHONATE

Abstract

Chestnut ink disease represents a great risk for chestnut (Castanea sativa Mill.) in all regions of chestnut production of Europe and North America. Induced by soil borne oomycetes, Phytophthora cinnamomi and P. cambivora, both parasites infect the root system and cause root and collar rot resulting in dieback, decline and finally, the death of infected trees. There are no single control measures for root rot pathogens and control with systemic and selective oomycetes biochemical substances can be important as part of the integrated disease management of these soil borne parasites. In this work we studied the effect of potassium phosphonate to protect roots from P. cinnamomi. Chestnut seedlings were planted in potting mix previously inoculated with P. cinnamomi (Pr 120). One group of five pots, with three seedlings each were submitted to potassium phosphonate foliar spraying (3 ml L -1 Atlante ® ) and another group of five pots were water foliar sprayed. Seedlings had been grown in a nursery for 120 days. At the end of the experiment, visual symptoms of the crown and root system were assessed. Parameters related with roots: root length, root rot length, root number, root rot number, crown diameter, height and biomass were evaluated. Statistic significant differences between treatments were obtained in all root studied variables. Potassium phosphonate by foliar spraying prevented P. cinnamomi infections of roots of chestnut and can be a key factor in the management of ink disease of chestnut.