Preliminary results of rootstock evaluation for Estonian sweet cherry cultivar ‘Anu’

Mahaleb cherry (Prunus mahaleb L.) is the most widely used rootstock for sweet cherries in Latvia, however it has several disadvantages - strong vigour of grafted trees and an intolerance to heavy, waterlogged soils. The aim of the study was to test the suitability of rootstocks of different origins for winter-hard sweet cherry cultivar in Latvian climate. The trial was established in the spring of 2014 at the Institute of Horticulture (LatHort) to test four clonal rootstocks: ‘PiKu 1’, PHL-A’, ‘GiSelA 5’, ‘VSL-1’, and generative rootstock P. mahaleb (control) grafted with cultivar ‘Anu’ (Estonian breeding). Cherries were planted at 5×3.5 m in a random block design in three replications with three trees per plot. Tree height, annual growth of shoots, the viability of trees after wintering period and the intensity of flowering and production were evaluated in 2016–2019. Sweet cherry cultivar ‘Anu’ had the best overall winter-hardiness in the combinations with rootstocks ‘GiSelA 5’ and P. mahaleb. The highest intensity of flowering and production were observed in trees grafted on ‘GiSelA 5’. Trees on ‘VSL-1’ had the highest decease rate and the lowest winter hardiness

SSR-Based Analysis of Genetic Diversity and Structure of Sweet Cherry (Prunus avium L.) from 19 Countries in Europe

Sweet cherry (Prunus avium L.) is a temperate fruit species whose production might be highly impacted by climate change in the near future. Diversity of plant material could be an option to mitigate these climate risks by enabling producers to have new cultivars well adapted to new environmental conditions. In this study, subsets of sweet cherry collections of 19 European countries were genotyped using 14 SSR. The objectives of this study were (i) to assess genetic diversity parameters, (ii) to estimate the levels of population structure, and (iii) to identify germplasm redundancies. A total of 314 accessions, including landraces, early selections, and modern cultivars, were monitored, and 220 unique SSR genotypes were identified. All 14 loci were confirmed to be polymorphic, and a total of 137 alleles were detected with a mean of 9.8 alleles per locus. The average number of alleles (N = 9.8), PIC value (0.658), observed heterozygosity (Ho = 0.71), and expected heterozygosity (He = 0.70) were higher in this study compared to values reported so far. Four ancestral populations were detected using STRUCTURE software and confirmed by Principal Coordinate Analysis (PCoA), and two of them (K1 and K4) could be attributed to the geographical origin of the accessions. A N-J tree grouped the 220 sweet cherry accessions within three main clusters and six subgroups. Accessions belonging to the four STRUCTURE populations roughly clustered together. Clustering confirmed known genealogical data for several accessions. The large genetic diversity of the collection was demonstrated, in particular within the landrace pool, justifying the efforts made over decades for their conservation. New sources of diversity will allow producers to face challenges, such as climate change and the need to develop more sustainable production systems