Response of Herbaceous and Woody Plant Species in Southern Portugal to Cope Oak Decline Associated to Phytophthora cinnamomi

Abstract

The decline of oak canopies in Iberian woodlands is strongly influenced by abiotic and biotic stress factors, such as the oomycete Phytophthora cinnamomi which has the capacity to infect a wide range of plant species. Understory plant diversity plays an important role in the epidemiology of P. cinnamomi in these ecosystems. This study aimed to identify a set of woody and herbaceous plants that can impact oak decline. Twenty-two herbaceous plant species from three families, and nineteen woody plants (trees and shrubs) from seven families were assessed for their response to infection by P. cinnamomi. Most of the herbaceous species did not show evident susceptibility, only a few exhibited significant biomass root reduction and just seven were identified as hosts. Yellow lupin was the only herbaceous species showing high susceptibility. Among the woody plant species, only two shrub and two tree species exhibited disease symptoms. The other ones, mostly hosts, ranged between low susceptible and tolerant. These results highlight the possibility that many of these species can maintain the pathogen active in the soil or even increase its population. In this context, the findings of this study can contribute to effective management strategies to mitigate Phytophthora infection in woodland soils.