Reliable detection of unevenly distributed Verticillium dahliae in diseased olive trees

Abstract

Verticillium wilt caused by Verticillium dahliae is one of the most threatening diseases of olive worldwide. For preplanting and post-planting control of verticillium wilt in olive trees, availability of a rapid, reliable and non-destructive method for detection of V. dahliae is essential. For such a method, suitable and easily performed sampling and efficient processing of samples for extraction of DNA are necessary. In this study, the suitability of young twig and leaf samples of olive trees, which are easy to collect and extract DNA from, were assessed for the detection of V. dahliae in routine procedures. The lower (about 50 cm from the tip) and top parts (about 5 cm from the tip) of twigs, as well as leaves from infected olive trees were screened for V. dahliae infection and distribution using real-time PCR. The biomass of V. dahliae detected in individual twigs was highly variable, but there was no significant difference between mean quantities of V. dahliae DNA detected in top and lower parts of twigs. Furthermore, it was demonstrated that analysis of combined samples containing DNA extracted from five twigs of an infected tree accurately detected the presence of the pathogen. Similarly, testing combined samples of 5-10 leaves enabled reliable detection of the pathogen in an infected tree. The development of this assay enables reliable detection of V. dahliae in infected olive trees that can aid in management decisions for the implementation of integrated disease management.

Use of RGB Vegetation Indexes in Assessing Early Effects of Verticillium Wilt of Olive in Asymptomatic Plants in High and Low Fertility Scenarios

“…Verticillium Wilt of Olive (VWO), a vascular disease caused by the pathogenic soil-borne fungus Verticillium dahliae Kleb, is one of the most severe threats to olive production today [1]. Taxonomic classifications place this fungus in Division Ascomycota, Class Sordariomycetes, Subclass Hypocreomycetidae, Order incertae sedis, Family Plectosphaerellaceae [2].…”

A split-root system to assess biocontrol effectiveness and defense-related genetic responses in above-ground tissues during the tripartite interaction Verticillium dahliae-olive-Pseudomonas fluorescens PICF7 in roots

“…individual olive plants) in previous studies (Gómez-Lama Cabanás et al 2014), regardless of whether plants originated from the same propagation batch at the nursery and inoculation procedures were performed with all cautions. This sampling strategy has been also used to increase reliability of in planta V. dahliae molecular detection procedures (Karajeh and Masoud 2006;Keykhasaber et al 2016). Even though some of the RE patterns here obtained would require a deeper knowledge of defense responses in olive for proper explanation, the development of the olive split-root system offered for the first time the possibility to study systemic responses triggered during a tripartite interaction taking place at the belowground level.…”

Effect of Cultivar Resistance and Soil Management on Spatial–Temporal Development of Verticillium Wilt of Olive: A Long-Term Study

“…In this country, the major area of olive groves covers around 1.65 million hectares and is located in Andalusia, Southern region, being one-third concentrated in the province of Jaen (ESYRCE, 2019). Verticillium wilt of olive, caused by the soil-borne pathogen Verticillium dahliae Kleb., is a major concern for the producers of this crop worldwide (Lopez-Escudero and Mercado-Blanco, 2011;Tsror, 2011;Keykhasaber et al, 2017). In Spain, the increase and spread of Verticillium wilt of olive have been mainly driven by (i) the olive colonization of soils historically cropped with cotton, which is a major host of V. dahliae; and (ii) the spread of the defoliating (D) pathotype of the pathogen, which is more virulent than the previously dominant non-defoliating pathotype (ND) (Navas-Cortes et al, 2008;Lopez-Escudero et al, 2010;Milgroom et al, 2016).…”

“…In the disease cycle of Verticillium wilt of olive, the pathogen has a parasitic phase in the host and a non-parasitic phase as microsclerotia (Keykhasaber et al, 2017), which can survive in the field soils for a prolonged period (up to 15 years) (Wilhelm, 1955). Microsclerotia germinate under favorable microbiological and environmental conditions and in the presence of root exudates of olive infect the roots (Prieto et al, 2009;Jimenez-Diaz et al, 2012).…”

“…After planting, control measures may include (i) the elimination of alternative weed hosts to avoid the increase in pathogen inoculum (Ligoxigakis et al, 2002); (ii) the removal of pruning remains by burning (Morello et al, 2016); (iii) the application of disinfectants to reduce the viability of the pathogen in the irrigation water ; or (iv) biofumigation by sowing Brassicaceae species and/or solarization because both strategies reduce pathogen inoculum density in the soil (Tjamos, 1991;Lopez-Escudero and Blanco-Lopez, 2001;Bejarano-Alcazar, 2008). The use of an IDM strategy to control Verticillium wilt of olive has been highly recommended for many authors (Lopez-Escudero and Mercado-Blanco, 2011;Jimenez-Diaz et al, 2012;Keykhasaber et al, 2017;Montes-Osuna and Mercado-Blanco, 2020); however, the examination of an IDM strategy controlling the disease in a commercial olive orchard and the long-term effect in field conditions is needed. While spatiotemporal studies have highlighted their potential in understanding epidemics of soil-borne pathogens (Madden et al, 2007), these remain barely used in Verticillium wilt of olive and limited to the moderately susceptible cultivar Arbequina in experimental plots (Navas-Cortes et al, 2008).…”