Verticillium wilt of olive: a case study to implement an integrated strategy to control a soil-borne pathogen

Abstract

Olive (Olea europaea L.) is one of the first domesticated and cultivated tree species and has historical, social and economical relevance. However, its future as a strategic commodity in Mediterranean agriculture is threatened by diverse biotic (traditional and new/emerging pests and diseases) and abiotic (erosion, climate change) menaces. These problems could also be of relevance for new geographical areas where olive cultivation is not traditional but is increasingly spreading (i.e., South America, Australia, etc). One of the major constraints for olive cultivation is Verticillium wilt, a vascular disease caused by the soil-borne fungus Verticillium dahliae Kleb. In this review we describe how Verticillium wilt of olive (VWO) has become a major problem for olive cultivation during the last two decades. Similar to other vascular diseases, VWO is difficult to manage and single control measure are mostly ineffective. Therefore, an integrated disease management strategy that fits modern sustainable agriculture criteria must be implemented. Multidisciplinary research efforts and advances to understand this pathosystem and to develop appropriate control measures are summarized. The main conclusion is that a holistic approach is the best strategy to effectively control VWO, integrating biological, chemical, physical, and cultural approaches.

Genetic and Molecular Approach to Verticillium dahliae Infecting Sunflower

“…scolymus), cotton (Gossypium hirsutum L.), eggplant (Solanum melongena L.), lettuce (Lactuca sativa L.), olive tree (Olea europaea L.) and tomato (Solanum lycopersicum L.) among others (Pegg and Brady, 2002). In Spain, Verticillium constitutes an important constraint for the production of cotton, artichoke, and, particularly, of olive tree (Bejarano-Alcázar et al, 1996;Korolev et al, 2001;Jiménez-Díaz et al, 2006;Navas-Cortés et al, 2008;Berbegal et al, 2010;Jiménez-Díaz et al, 2011;López-Escudero and Mercado-Blanco, 2011).…”

Verticillium wilt caused by Verticillium dahliae in woody plants with emphasis on olive and shade trees

“…Later olive cultivation expanded to the Americas, South Africa, China, Japan and Australia (Blázquez-Martínez 1996;Civantos 2004). Verticillium wilt of olive was first reported from Italy (Ruggieri 1946), and soon thereafter from various other regions, including California, European and Asian countries as well as Australia (López-Escudero and Mercado-Blanco 2011;Navas-Cortés et al 2008), and Argentina (Docampo et al 1981). Initially, Verticillium wilt mostly occurred in olive groves that were established in fields that were previously used for cultivation of crops that are susceptible to V. dahliae, especially cotton, or in groves established next to fields with susceptible crops .…”

“…Currently, Verticillium wilt is considered as the most important disease that threatens olive production, causing serious concern to growers, nursery companies and the olive-oil industry throughout the world (López-Escudero and MercadoBlanco 2011;Jiménez-Díaz et al 2012;Tsror 2011). This is particularly relevant since most olive cultivars are susceptible to V. dahliae (Antoniou et al 2001(Antoniou et al , 2008Cirulli et al 2008;López-Escudero et al 2004;López-Escudero and Mercado-Blanco 2011), although a number of relatively resistant genotypes have been identified in artificial inoculation assays (García-Ruiz et al 2014;López-Escudero et al 2004;Martos-Moreno et al 2006) as well as in field experiments (López-Escudero and Mercado-Blanco 2011; Trapero et al 2013). However, most of the agronomically and economically relevant olive cultivars are susceptible or extremely susceptible to highly virulent strains of V. dahliae (López-Escudero and Mercado-Blanco 2011).…”

“…The bark of affected shoots may become reddish-brown, and the inner vascular tissues show a dark-brown discoloration. These symptoms usually begin in spring and slowly progress to early summer Jiménez-Díaz et al 2012;López-Escudero and Mercado-Blanco 2011).…”

“…V. dahliae isolates have been classified into six VCGs (VCG1 through VCG6). VCG1, VCG2 and VCG4 were further divided into subgroups A and B based on the frequency and vigour of complementation (Chandelier et al 2003;Chen 1994;Dervis et al 2010;Goud and Termorshuizen 2002;Jiménez-Díaz et al 2006;Jiménez-Díaz et al 2011;Jiménez-Díaz et al 2012;Korolev et al 2000Korolev et al , 2001Korolev et al , 2008López-Escudero and Mercado-Blanco 2011). So far, vast numbers of V. dahliae isolates from maple, ash, olive and some other woody hosts in USA and Europe have been analysed through complementation tests and classified into VCG1A, VCG1B, VCG2A, VCG2B and VCG4B (Chandelier et al 2003;Chen 1994;Hiemstra and RatajGuranowska 2000;Jiménez-Díaz et al 2011;Jiménez-Díaz et al 2012;Neubauer et al 2009).…”