Blanca Landa. IAS/CSIC

The phytosanitary status of olive orchards in the Mediterranean is increasingly threatened by Vascular diseases; specifically, Verticillium wilt caused by the plant pathogenic fungus Verticillium dahliae (Vd) and Olive Quick Decline Syndrome caused by the fastidious bacterium Xylella fastidiosa (Xf). These pathogens can lead to significant losses in fruit yield and even tree death. Currently, there are no effective control measures available for both pathogens, and although host resistance is thought to be the most practical, sustainable and cost-efficient method for their management, its effectiveness is curtailed by several factors: i) the prevalence of a highly-virulent defoliating pathotype (D) of Vd in the Mediterranean; ii) the existence of various subspecies and sequence types of Xf with differing virulence and pathogenicity, some causing devastating effects on millions of olive trees; and iii) lack of enough knowledge on cultivar susceptibility to Xf subspecies coupled with the absence of a long-standing breeding program.

Research efforts are intensifying globally, particularly in Europe, to identify alternative or new in planta-based control measures for these diseases. These management practices can be used alone or in combination with host tolerance/resistance. Key ongoing research activities will be presented including: i) Disease suppressive soils to Verticillium wilt as a strategy for stimulating and supporting specific groups of antagonistic microorganisms in the rhizosphere, providing a first-line of defense against infection by Vd or as a source of microbial antagonists; ii) Use of resistant/tolerant olive rootstocks or cultivars to highly virulent strains of Vd or Xf, facilitating olive cultivation in geographic areas where those pathogen variants prevail; iii) Understanding and exploiting xylem-inhabiting olive microbiome to reduce the incidence of those Vascular diseases or the resilience of olive to their infection; iv) Use of remote sensing methods and molecular diagnostic tools to detect changes in plant functional traits or infection at the pre-visual disease symptoms stage, aiding to detect early pathogen infection early pathogen detection and monitoring of infected areas.

These research initiatives aim to secure the future of olive groves by developing effective, sustainable management strategies for combating the main vascular diseases threatening Mediterranean olive orchards.