Screening of Wild Olives for Verticillium Wilt Resistance

The use of resistant cultivars is considered one of the most important ways to control Verticillium wilt of olive in the framework of an integrated disease management strategy. However, only a reduced number of cultivars currently in use have shown a considerable level of resistance to the development of symptoms. Wild olives may represent a useful source of genetic variability for some traits, such as disease resistance, hardly found in cultivated material. In this work, 28 wild olive genotypes from different origins were screened in growth chamber under controlled environmental conditions to test their resistance to Verticillium wilt. Inoculation by dipping roots in a conidia suspension of a defoliating isolate of Verticillium dahliae was used, including cultivars 'Picual' and 'Frantoio' as susceptible and resistant control cultivars, respectively. Disease reaction was evaluated weekly by using a 0-4 severity scale. Some of the evaluated genotypes were classified as highly resistant on the basis of external symptoms development and percentage of dead plants. The most resistant ones will be propagated for future trials to confirm their disease reaction under both controlled and field conditions. Their possible use as rootstocks or genitors in breeding programs is discussed.