New approach to cherry rootstock selection in Serbia: a review

The main goal of this study was to develop reliable pre-selection methods for breeding low-vigor rootstocks well-adapted to arid continental climates. The Balkan Peninsula as a secondary center of origin provides great opportunities for cherry rootstock breeding. Biodiversity in natural populations of P. mahaleb, P. avium, and P. fruticosa are a rich source of genetic variability, providing unique, well adapted initial breeding material. 'Oblačinska' sour cherry is an ecotype, visible as a continuum of morphological characteristics, stemming from heterozygosity, self-compatibility and cross-pollination with related germplasm. An established network of collaborators is a valuable asset for germplasm preservation work and inexhaustible source of ideas. In several surveys and field collection trips, undertaken in 2007-2012, 95 accessions were selected in situ, with the most promising and interesting accessions collected and preserved ex situ. For accession mapping, a GPS record-keeping program was used. Efficient in vitro culture techniques were developed for quick introduction of new germplasm into the rootstock breeding program. Determination of total and active root surface area proved to be a reliable indicator of radial root system activity. Based on the anatomical measurements, theoretical axial hydraulic conductance of the total cross-sectional area was calculated for all plant constituents NDASH root, rootstock stem and scion - whose functional hydraulic conductance was used in the plant vigor simulation model. Functional root system hydraulic conductance represents theoretical value corrected for the coefficient of active surface area. Rootstock stem hydraulic conductance was corrected for the coefficient of inner ring hydraulic conductance due to the rootstock/scion pith overlapping. Estimated hereditary scion vigor represents water conductance of all three secondary wood rings. Based on these parameters, a pre-selection model of cherry dwarfing potential, as well as a methodological procedure for successive breeding phases, was proposed.