Field Resistance to Verticillium Wilt in Selected Olive Cultivars Grown in Two Naturally Infested Soils

Abstract

The resistance of 11 olive cultivars to Verticillium dahliae was assessed in two experimental field trials. One-year-old rooted olive cuttings from the World Olive Germplasm Bank (IFAPA research center, Córdoba, Spain) were planted in a heavily infested field in Utrera (Sevilla province) and in a moderately infested field in Andújar (Jaén province) of southern Spain. Plants were assessed for Verticillium wilt resistance during 22 months based on disease severity and tree growth. Severe disease symptoms were observed 6 months after planting in both trials. Twenty months after planting in the heavily infested soil, V. dahliae had killed nearly all of the trees of ‘Bodoquera’, ‘Cornicabra’, ‘Manzanilla de Sevilla’, and ‘Picual’, demonstrating the elevated risk of planting susceptible cultivars in a soil heavily infested with V. dahliae. ‘Arbequina’, ‘Koroneiki’, ‘Sevillenca’, and especially ‘Frantoio’, ‘Empeltre’, and ‘Changlot Real’ showed a high level of disease resistance. However, all of them were affected by the disease. Although the field results confirmed the level of resistance previously obtained for these olive genotypes under controlled conditions, there were some discrepancies. This information will be useful in managing the disease and also in selecting new cultivars for the breeding of Verticillium wilt resistance.

Evaluation of Verticillium wilt resistance in selections from olive breeding crosses

“…Slight difference was observed for 'Koroneiki', previously cataloged as MS ussing different inoculation methods (dipping root, soil infested and stem puncture) (López-Escudero et al 2007;Markakis et al 2010;AriasCalderón et al 2015) but categorized as R in this work. It should be noted that 'Koroneiki' cultivar has also showed high level of resistance under natural field conditions (Trapero et al 2013). A wide variability in the values of the different disease parameters calculated was observed in the three cross combinations tested and 10 out of 38 evaluated genotypes (26 %) were finally classified as R according to RSI values.…”

“…Several sources of resistance to VW have been identified in olive, including both cultivated and wild germplasm. Considerable levels of resistance to development of symptoms caused by the highly virulent defoliating (D) pathotype of V. dahliae have been reported for a limited number of traditional cultivars such as 'Frantoio', 'Changlot Real' and 'Empeltre', both upon artificial inoculations and in naturally-infested soils (López-Escudero et al 2004;Trapero et al 2013). However, due to some disadvantages such as late bearing and excessive vigour, these cultivars may not represent the best agronomical choice for a modern olive growing and are not suitable for high-density orchards.…”

“…In olive, the wide dispersion of the disease and the increase importance of crop losses associated with the rapid extend of fungal pathotypes highly virulent, together with the reduced number of traditional cultivars showing a significant level of resistance to VW, have promoted the development of breeding programs to select new cultivars with improved resistance levels to the disease (Erten and Yildiz 2011;Trapero et al 2013;Arias-Calderón et al 2015). However, even in progenies from crosses between cultivars of known merit, most of the seedlings obtained show poor agronomic performance and should be discarded as soon as possible.…”

Resistance to Verticillium wilt in olive progenies from open-pollination

“…Initial works by Wilhelm and Taylor (1965) indicated that the cultivars 'Frantoio' and 'Arbequina' yielded more resistant seedlings than the susceptible cultivars tested, but it was doubtful whether resistant progenies from resistant cultivars were more resistant than those derived from susceptible. Recent works have been also carried out to test seedlings from different crosses before their evaluation under field conditions (Trapero et al, 2013a).…”

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

“…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).…”