Intra-varietal variability and genetic relationships among the homonymic East Adriatic olive ( Olea europaea L.) varieties

Abstract The intensive exchange and diffusion of plant material over the whole Mediterranean Basin including the East Adriatic region, has contributed to the confusion in denomination of olive varieties, and formation of a large number of synonyms and homonyms. In the present study, we report on clonal diversity and genetic relationships among a total of 190 olive trees sampled along the East Adriatic coast in Slovenia (SVN), Croatia (HRV) and Montenegro (MNE). Samples belonged to the six East Adriatic olive varieties with homonymic denomination: ‘Istrska belica’ (SVN), ‘Bjelica’ (HRV), ‘Žutica’ (MNE), ‘Crnica’ (SVN), ‘Crnica’ (HRV), and ‘Crnica’ (MNE). Results showed polymorphism in all twelve microsatellite markers (DCA3, DCA9, DCA11, DCA14, DCA16, DCA18, EMO03, EMO90, GAPU101, GAPU103A, GAPU71B and UDO99-019), revealing a total of 83 alleles. A total of 36 different genotypes in the panel of 190 samples were found. Genetic profiling of six homonymic East Adriatic olive varieties revealed four different varieties: 1) ‘Istrska belica’ (SVN), 2) ‘Bjelica’ (HRV)/‘Žutica’ (MNE), 3) ‘Crnica’ (HRV)/‘Crnica’ (MNE) and 4) ‘Crnica’ (SVN). Detailed clonal and genetic relationship analyses demonstrated genetic uniformity of ‘Istrska belica’ (SVN), negligible low diversity of ‘Crnica’ (SVN), and moderate diversity of ‘Crnica’ (HRV)/‘Crnica’ (MNE). Polyclonal property was assigned to only ‘Bjelica’ (HRV)/‘Žutica’ (MNE) variety. High genetic similarity between ‘Bjelica’ (HRV)/‘Žutica’ (MNE), and ‘Crnica’ (HRV)/‘Crnica’ (MNE), with different distribution of clones within them, reflects the past selection and propagation processes in Croatia and Montenegro. For the first time, international synonymy of ‘Žutica’ (MNE) and ‘Bjelica’ (HRV), and homonymy of ‘Istrska belica’ (SVN) and ‘Bjelica’ (HRV)/‘Žutica’ (MNE), as well as ‘Crnica’ (SVN) and ‘Crnica’ (MNE, HRV) were reliably confirmed with DNA markers.