Developments in Detection Methods and Uncovering Resistant Agents Against Verticillium dahliae Imply for Effective Protection of Trees in Practice

Verticillium wilt, caused by Verticillium dahliae Kleb., is a serious problem in tree nurseries and plantations worldwide. The best measure to control Verticillium wilt disease is using healthy planting material, and the deployment of resistant plants when V. dahliae is already present in the field. However, V. dahliae can thrive as an endophyte in plant hosts and asymptomatic infections may occur in recently infected plants that do not yet display symptoms. Therefore, reliable methods, such as PCR-based in planta detection methods, should be used for detection of the pathogen in plant material prior to planting to ensure use of healthy plant material and to avoid the introduction of pathogens in non-infested growing areas. In addition, in some trees recovery is enhanced by producing new vascular tissue, which allows novel vegetative growth of affected stems and branches. Studying the genes involve in recovery, and their impact on Verticillium-triggered changes in differentiation of cells from the cambium or even within existing tissues, may help to design strategies to stimulate recovery of susceptible trees. Identification of genetic sources of resistance is also an essential need for improving resistant trees aiming the effective control of Verticillium wilt in tree plantations. The discovery of candidate genes for disease resistance in trees based on genomics and transcriptomics, coupled with advancements in breeding technology, is expected to enable us to improve resistance particularly in commercially propagated valuable tree species such as olive in the future