Effect of phosphoric fertilization on the resistance of holm oak and cork oak to Phytophthora cinnamomi Rands.

Abstract

The oomycete Phytophthora cinnamomi Rands is the mean responsible for oak decline in southern Spain. This paper investigates the relationship between phosphoric fertilization of Quercus ilex and Q. suber seedlings and resistance to the disease caused by Phytophthora cinnamomi. The study was conducted on holm oak and cork oak seedlings previously submitted to a phosphoric fertilization programme involving four different treatments, namely: Phosphate-A (3 mg P2O5 seedling), Phosphate-B (6 mg P2O5 seedling), Phosphite (0.15 mg de P2O5 seedling) and No Fertilization. Tests were conducted in greenhouse over a period of 7 months and a number of treatments to plants inoculated with Phytophthora cinnamomi Rands. were applied, assessing the changes in their morphological (viz. height, root and collar diameter, and secondary root biomass) and physiological characteristics (viz. leaf nutrient contents). Based on the results, phosphate failed to improve plant resistance to P. cinnamomi; by contrast, phosphite successfully avoided infection by this pathogen. In fact, the phosphitetreated plants exhibited a morphological and physiological status similar to or even better than that of the non-inoculated controls. The protective effect of phosphite against P. cinnamomi can be achieved by applying it during seedling cultivation in nurseries.