Sanitary selection and molecular charecterization of olive cultivars grown in Apulia

Sanitary selection and molecular characterization programs are being implemented in Apulia (Southern Italy) to identify true-to-type and sanitarily improved (virus-tested and virus-free) olive stocks, complying with national and international quality requirements. The following activities are in progress: (i) selection of individual trees in pre-selected groves; (ii) assessment of the sanitary status of field-selected accessions by laboratory tests; (iii) identification of AFLP (Amplified Fragment Length Polymorphism) and SSR (Simple Sequence Repeats) markers suitable for the molecular characterization of selected genotypes; (iv) setting up efficient protocols for virus elimination; (v) obtention of "primary sources" (nuclear stocks) liable to enter certification programs. Due to the widespread occurrence of latent virus infections, visual inspections are unreliable, thus field observations need to be complemented by laboratory tests. Doublestranded RNA (dsRNA) analysis, RT-PCR, and molecular hybridisation were successfully used to test a large number of samples collected in commercial orchards. In order to characterize genotypes and establish their genetic relationships, olive accessions were screened with three AFLP primer combinations and twenty-seven SSR primer pairs. A comparison was done between AFLP and SSR marker variability, their efficiency and usefulness for establishing genetic relationships and cultivar identification. The data obtained were worked out with the Jaccard genetic similarity coefficient, applying the SAHN clustering method. The resulting dendrograms showed that all genotypes could be unequivocally distinguished. Because the sanitary status of very few of the selected plants conformed to legislative health requirements, most of the selected accessions underwent sanitation by in vitro meristem tip culture, in vivo and in vitro heat therapy, and rapid in vitro subculturing of shoots tips. The preliminary results have shown that some local varieties can be readily grown and multiplied in vitro while heat therapy and shoot tip culture are useful for eliminating some of the olive infecting viruses.