Abstract— In order to investigate the resistance of some olive (Olea europaea L.) cultivars and hybrids to leaf spot disease caused by Venturia oleaginea, this study was conducted on high susceptible cultivar Meski and nine hybrids. Samples were collected from a field site located in Nabeul (North East of Tunisia) and evaluated for their susceptibility to leaf spot disease by means of visible and latent infection. Therefore, the studied plants were classified into three categories: very susceptible, intermediate and resistant. Meski cultivar and three hybrids (MxA) obtained through controlled crosses between Meski and Arbequina were the most susceptible to the disease. The hybrids MxC resulting from the crosses between Meski and Chétoui olive cultivars presented less severity. However, the hybrids obtained through crosses between Meski and Picholine cultivars showed the lowest incidence of infection. Microsatellites were used as markers to analyze the genetic relationships between parental olive cultivars and hybrids and the effects of crossing on the disease resistance. Cluster analyses, using the SSR data, showed that olive cultivars and hybrids obtained by controlled cross between MeskixPicholine, Meski x Arbequina and Meski ×Picholine were related to Picholine cultivar. The hybrid Meski x Chétoui was more related to cultivar Meski. Data analyses revealed that the GAPU101 showed the highest number of alleles (8) followed by the tow loci UDO99 and GAPU71 with 6 alleles. The DCA18 locus showed 5 alleles. Genetic variability was wide as indicated by the values of observed heterozygosity as noted 1.00 at locus of the four studied loci. Polymorphic information content (PIC) varied from 0.669 to 0.776. The gene diversity values were higher than 0.53. Genetic distances were determined based on the SSR genotype data and component principal analysis were used for finding possible correlation between severity disease, Meski cultivar and hybrids.
Keywords— Olive, Venturia oleaginea, microsatellites, Genetic relationships, Disease resistance.
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