Title: Monitoring of clonal fidelity of highbush blueberry cultures propagated by axillary and adventitious shoots
Plant tissue culture technology is being widely used for large scale highbush blueberry plant multiplication. The main aim of micropropagation is the clonal production of 'true-to-type' plants. However, in vitro conditions induce somaclonal variations which can affect the undesired morphological and genetic changes of regenerated plants. Somaclonal variation, either genetic and epigenetic or combination of both, is influenced by the genotype, explant type, culture medium or age of the donor plants. The occurrence of callus and adventitious shoots during the in vitro culture of blueberries is mainly considered as a source of somaclonal variation. In blueberry in vitro cultures, adventitious shoots occur spontaneously and are common. To monitor clonal fidelity the differences between the in vitro cultures of the highbush blueberry ‘Brigitta blue’ plants derived from axillary (Ax) and adventitious shoots (Ad) using as an explant, were investigated. The two types of culture: the axillary shoots derived cultures (Ax-TC) and the adventitious shoots derived cultures of highbush blueberries plants (Ax-TC) were analysed during 3 subsequent passage. The analyses were carried out in the determination of morphological and molecular differences between Ax-TC and Ax-TC cultures. On the morphological level, the frequency and the length of the axillary shoots and adventitious ones were determined. Molecular studies were based on the methylation-sensitive amplification polymorphism (MSAP) technique. We indicated significant differences in studied traits like the ratio of Ax shoots in culture and the number of cultures that developed exclusively Ax shoots. Additionally, short adventitious shoots (< 1,5 cm in length) in Ad-TC cultures occurred more frequently in comparison to Ax-TC. What is more, different DNA methylation status among studied plants was revealed.