Response to Verticillium dahliae infection in a genetically diverse set of olive cultivars

Understanding the interaction between the soil-borne fungal pathogen Verticillium dahliae and olive is one of the major concerns for breeders and plant pathologists due to the wide variability in the disease response observed among cultivars. In this work, 40 representative olive cultivars of The World Olive Germplasm Bank of Cordoba (WOGBC, Spain) and six bred selections of IFAPA breeding program have been evaluated for the infection of the defoliating pathotype of V. dahliae under homogeneous conditions. The disease response has been characterized considering different traits of the disease development. Traits such as the relative area under disease progression curve (RAUDPC), the slope of the disease progression curve, the final dead plants and the ratio DNAV.dahliae/ DNAolive showed a positive correlation with the susceptible genotypes, whereas the incubation period (IP), the final asymptomatic plants and the survival time were positively correlated to the resistant ones. Nonetheless, the DNA ratio detected in infected plants was highly variable. The clustering analysis considering all these param-eters divided the genotypes in resistant and susceptible clusters. Cultivars like Abbadi Abou Gabra', Abou Salt Mohazam', Chemlal del Kabylie', Jabali', Llumeta', Majhol-152', Mastoidis', Menya', and Temprano' resulted extremely susceptible whereas Frantoio', FrxAr_5', FrxAr_6', and KorOp_48'. resulted highly resistant. This study highlights the variability to the Verticillium wilt response of the most representative cultivars of the WOGBC and the relevance of breeding programs developing new cultivars with improved resistance characteristics.