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.

At the colder peach production regions it is important to know the cold hardiness of peach cultivars at different phenological stages of flowering. In our experiment, artificial freezing tests were conducted in a climate chamber in five selected years between the period of 2007 and 2016 to determine the freeze tolerance of generative organs of three peach cultivars (‘Venus’, ‘Redhaven’, ‘Piroska’) at different phenological stages of bloom. Based on the results of the laboratory freezing tests LT₅₀ values were calculated. Our results showed that LT₅₀ values of examined peach cultivars in swelled bud stage averaged over five years were between –6.8 and –11.2°C according to cultivar, and as phenological phases progressed, cold hardiness of generative organs decreased. At the end of bloom LT₅₀ values varied between –1.7 and –4.1°C. Cultivar ‘Piroska’ had the highest freeze tolerance and cultivar ‘Venus’ showed the lowest in each year studied. This study shows that trees with delayed development are more prone to cold damage to flowers.

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Molecular marker analysis can be an effective tool when searching for new fire blight resistance donors. It can speed up the breeding process as well, even though many of the available markers linked to fire blight resistance QTLs have not yet been tested by screening a large number of cultivars. The aim of this study was to search for alternate sources of the three major QTLs of fire blight resistance; FBF7, FB_MR5 and FB_E, as well as to test the efficiency of some markers linked to minor QTLs. Altogether, nine primer pairs were used on 77 genotypes including new Hungarian cultivars and old apple cultivars from the Carpathian basin. Several marker alleles of FB resistance QTLs have been detected in the screened genotypes, most importantly the alleles coupling with FB_MR5 in the old cultivars ‘Kéresi muskotály’, ‘Szabadkai szercsika’ and ‘Batul’. We propose these cultivars as the first available resistance donors of FB_MR5 instead of the crabapple Malus × robusta 5. The results also bring new information regarding the resistance alleles of new Hungarian cultivars and selections.

Sour cherry is one of the most important horticultural crops in the Hungarian market. Its flavour combination makes it ideal for fresh consumption as well as canned products. The Hungarian and European markets have requested for new varieties to be introduced, making the evaluation of breeding and prebreeding material a crucial point. A total of 30 sour cherry accessions from the genebank collection were investigated for their potential inclusion into the breeding program. The main aim of the study was to identify candidates for future breeding programs, selecting their colour profiling and total polyphenolic content (TPC). This study follows the antioxidant activity of cherry species by determining the total content in polyphenols. Polyphenols are found in higher concentration in cherries when compared to other plants and have been identified as free radical scavengers, which are useful to prevent the occurrence of several diseases. Furthermore, TPC has been observed as a contributor of bitterness, acidity, colour, flavour, odour, and oxidative stability. The accessions were evaluated for their colour, fruit weight, flavour profile, firmness, and TPC. Colorimetric data were compared among four methods to illustrate to the Hungarian breeders which of the available approaches is the most accurate for sour cherry breeding. Results suggested that several accessions appear relevant for the breeding program, such as ‘Pipacs 1′, ‘Bosnyák’, ‘Hortenzia Királynője’, and ‘Mogyoródi Kései’. The total polyphenolic content was highest in ‘Pipacs1′ and lowest in ‘Kántorjánosi 3′. ‘Pipacs 1′ and ‘Hortenzia Királynője’ had interestingly high acidity content and light to very light fruit colours. ‘Bosnyák’ had a deep and dark colour with high soluble sugar content. ‘Mogyoródi Kései’ appears to have the biggest fruit. All mentioned varieties will be included in future breeding programs.