Health status assessment of the Serbian autochthonous plum cultivars for cryopreservation purposes

The conservation of genetic diversity and its sustainable use are essential to meet a number of challenges facing humanity. European plum (Prunus domestica L.), as the leading fruit species in Serbian agriculture, is facing with climate changes and long-term inoculum pressure of numerous pathogens. In order to identify the trees as a source for cryopreservation using vitrification-based techniques (V and D cryo-plate) we collected samples from nine autochthonous cultivars. A total of 140 samples of 'Belosljiva', 'Crvena Ranka', 'Crnosljiva', 'Cerovacki Piskavac', 'Dragacevka', 'Moravka', 'Pozegaca', 'Sitnica' and 'Trnovaca' plums were collected from various geographical locations in Serbia that are considered as their origin. Samples were collected from symptomless trees showing typical pomological characteristics of the cultivars (true-to-type). All samples were tested for the presence of Plum pox virus (PPV), Prune dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV), Apple chlorotic leaf spot virus (ACLSV), Apple mosaic virus (ApMV), Plum bark necrosis stem pitting-associated virus (PBNSPaV), Myrobalan latent ringspot virus (MLRSV) and 'Candidatus Phytoplasma prunorum'. The analysis for the virus presence was performed by ELISA and RT-PCR test. Samples were additionally tested for PPV presence by Real-time PCR, whereas 'Candidatus Phytoplasma prunorum' was detected by nested-PCR. Of all analysed pathogens, only PPV was detected in 6 samples. The presented results showed that, even in the high virus inoculum pressure, it is possible to select virus-free trees from existing old orchards. After analysis, selected healthy trees were used as a source of explants for the establishment of aseptic culture of each genotype for the conservation purpose.