Evaluation of cork and holm oak seedling viability to Phytophthora cinnamomiinfection treated with compost and mycorrhizae fungi

Abstract: Phytophthora cinnamomi is a soil borne plant pathogen involved in oak decline thatcaused a high mortality in cork oak and holm oak trees in Portugal. We evaluated thedevelopment of oak seedlings from different origins submitted to different treatments. Acornswere collected in 12 regions of Portugal and Spain. A direct sowing was carried out followingtwo treatments: 1) in soil naturally infested with P. cinnamomi; 2) in the same soil corrected withthe addition of chemically and microbiologically characterized vegetal compost. In greenhouse,pre-germinated acorns were sown in pots filled with: A) a mixture of a soil naturally infested withP. cinnamomi, collected from a field with high disease incidence; B) the same mixture plus avegetal compost; C) the same mixture as A inoculated with mycorrhizae fungi collected fromcork oak stands. Preliminary results from evaluation at six months showed that the compostimproved the germination of both species in field conditions, even in the presence of P.cinnamomi. Under controlled conditions, a better development was observed on infected oakseedlings submitted to the compost treatment. These preliminary results suggested that usingcompost is a useful cultural practice that may reduce P. cinnamomi impact.