Biological control of Verticillium wilt of olive within an integrated disease management framework

Abstract

Verticillium wilt is one of the most serious biotic threats for olive cultivation, the disease being a severe problem in some traditional olive-cultivating regions within the Mediterranean Basin. Control of VWO is difficult and none of the available control measures is effective enough when applied individually. Therefore, an integrated disease management strategy is the only plausible framework for an effective control of VWO. The use of biological control agents (BCAs) can be considered either as a before-planting (preventive) or as a post-planting (palliative) action in established olive orchards. It is an approach that could be used in combination with other control tools. So far, only a few bacteria and fungi species have been examined as potential BCAs against VWO. Our studies have proved that some indigenous Pseudomonas spp. strains of olive roots, some of them with an endophytic lifestyle, are effective against VWO caused by the highly-virulent, defoliating (D) pathotype. An interesting field to be explored is the development of bioformulations which may combine BCAs with different biocontrol mechanisms operating synergistically; for instance, induction of systemic resistance triggered by an endophyte and antibiosis by a root-surface colonizer. However, how biocontrol actions can be effectively implemented within this integrated framework still needs of in-depth studies aimed to unravel the genetic and molecular basis underlying the olive/BCAs/V. dahliae tripartite interaction, as well as to understand how (a)biotic factors may influence this system under field conditions.