Influence of management system in the natural suppressivenessof olive orchards soils to the soilborne plant pathogen Verticillium dahliae

Abstract: Olive (Olea europaea L. subs. europaea) is one of the most important crops in Spainwith > 2.4 million ha. During the last two decades phytosanitary status of olive orchards is beingthreatened due to some diseases caused by soilborne pathogens, mainly Verticillium wilt (VW)caused by Verticillium dahliae (VD) which is steadily increasing both in severity and extension.The main objective of this study was to determine the effect of olive management system on thenatural suppressiveness of olive orchards soils to VD and how this may be related with biologicaland functional indicators of soil quality. An in planta bioassay was developed for assessing thenatural suppressiveness to VD of a collection of 93 soils using highly conducive conditions for VWdevelopment. Results showed a wide range of variation among the different soils in their ability tosuppress VD, with 25.8, 49.5 and 24.7% of soils showing low, moderate and high suppressivenessaccording to the VW severity developed in the test plants growing in those soils compared to thatdeveloped in plants in sterile and pasteurized artificial soils. Canonical multivariate discriminantanalysis is being used to identify physicochemical, functional or biological indicators that may beinvolved in the natural suppression to VD of those soils.