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International audience; Apple scab, caused by Venturia inaequalis, is a major fungal disease worldwide. Cultivation of scab-resistant cultivars would reduce the chemical footprint of apple production. However, new apple cultivars carrying durable resistances should be developed to prevent or at least slow the breakdown of resistance against races of V. inaequalis. One way to achieve durable resistance is to pyramid multiple scab resistance genes in a cultivar. The choice of the resistance genes to be combined in the pyramids should take into account the frequency of resistance breakdown and the geographical distribution of apple scab isolates able to cause such breakdowns. In order to acquire this information and to make it available to apple breeders, the VINQUEST project (www.vinquest.ch) was initiated in 2009. Ten years after launching this project, 24 partners from 14 countries regularly contribute data. From 2009 to 2018 nearly 9000 data points have been collected. This information has been used to identify the most promising apple scab resistance genes for developing cultivars with durable resistance, which to date are: Rvi5, Rvi11, Rvi12, Rvi14 and Rvi15. As expected, Rvi1, together with Rvi3 and Rvi8, were often overcome, hence have little value for scab resistance breeding. Rvi10 may also belong to this group. On the other hand Rvi2, Rvi4, Rvi6, Rvi7, Rvi9, and Rvi13 are still useful for the breeding, but their use is recommended only in extended pyramids of (≥3) resistance genes.

In this paper, the microsatellite (SSR) loci analysis was used to study apple genotypes with different levels of ploidy. A total of 47 samples were studied (9 diploids, 21 triploids, and 17 tetraploids) for seven microsatellite loci (GD147, Hi02C07, CH02c11, CH04c07, CH03d07, CH02c09, and GD12). It was possible to refine the pedigrees for some forms. It was established that the tetraploidss 20-9-30 and 20-9-27, selected in a hybrid family from the crossing of Wealthy 4x and Antonovka Obyknovennaya, were probably obtained from the self-pollination of the maternal form, since in the most loci they did not inherit alleles from the paternal form. As a result of the alleles distribution analysis, the spontaneous triploid cultivars Nizkorosloe and Sinap Orlovsky were revealed to be formed from the merge of an unreduced ovum and haploid pollen, since in the heterozygous loci both alleles are inherited from the maternal form and only one from the paternal form. According to the obtained data, studied tetraploids may be divided into two groups, which also reflect the features of tetraploids origin. The first group includes tetraploids inherited alleles from one initial diploid form (including spontaneous and induced tetraploids, as well as forms from self-pollination of the tetraploid maternal form). These teraploids, like diploids, amplify 1–2 alleles per locus (on average, for all 7 loci, one genotype amplifies 13 alleles). The second group includes tetraploids carrying alleles from several initial diploid forms. Tetraploids of this group are highly heterozygous and amplify 3–4 alleles at most loci (the maximum number of alleles at all loci, 24 alleles, was identified in the form 30-47-88). Tetraploids of the second group have a greater potential for the genetic diversity of its offspring. Analysis of polymorphism of microsatellite loci can be used (1) as an alternative or additional method for identifying the triploid hybrids from heteroploid crosses of orthoploid forms, which is based on the analysis of the loci most polymorphic in parental forms, and (2) for the analysis of true hybridity (verification of pedigrees), including tetraploid forms. Moreover, we identified the most polymorphic loci suitable for the above purposes. The aspects of qualitative and quantitative interpretation of the fragment analysis of microsatellite loci results are considered. The possibilities and limitations of the SSR analysis for detection of apple ploidy level are discussed.

Based on the analysis of SSR loci, the genetic similarity of 32 pear cultivars (Pyrus) from the VNIISPK collection was studied. A cluster analysis of the genetic similarity of genotypes was carried out using 19 microsatellite markers. Based on the data obtained, a dendrogram was constructed using the UPGMA method using the Jacquard coefficient and bootstrap (BP) analysis. The coefficients of pairwise genetic similarity between the varieties ranged from 0.4 (between Podgoryanka and the Bere Russkaya, Mramornaya group) to 0.85 (between Osennyaya Zheltaya and Pervomayskaya). This group had a high BP level– 100% and a close genetic distance – 0.85), and the reliability level (BP,%) was indicated on the dendrogram at a value of more than 50%. According to the clustering results, the pear samples did not form large groups with high BP, which indicated the sufficient genetic diversity of the studied cultivars. There are only three small groups with high BP. Two of them combined two cultivars with a common origin. Thus, Bere Russkaya and Mramornaya, which are descendants from the crossing of Bere Zimnya Michurina × Lesnaya Krasavitsa, joined into one cluster with BP 82. Another group with BP 92 united Viliya and Zaveya, which also have the same origin ([Belorusskaya Pozdnya × (Bere Seraya × Dulya Ostzeyskaya)] × Maslyanaya Ro). The third group combined the cultivars Osennyaya Zheltaya (origin is not known) and Pervomayskaya (Doch Zari × Pozdnya MOSVIR) with BP 100 and the cultivar Prosto Maria ([Belorusskaya Pozdnya × (Bere Seraya × Dulya Ostzeyskaya)] × Maslyanaya Ro) with BP 100 adjoins them at a extended genetic distance. There is no obvious similarity in origin in this cluster. The SSR-analysis method opens up broad prospects in studying the genetic similarity of cultivars.

This paper gives the development history of the best apple cultivar of the temperate zone of Russia— the Sinap Orlovsky apple cultivar with fruit of a long storage life, which has hitherto been considered to be a diploid one. The assumption of its triploidy has come into existence due to DNA-markers. Cytoembryological studies showed in 2016 that the cultivar was a triploid. It is characterized by vigorousness and regular fruit bearing. The long-term experimental data show that the cultivar is of little promise as an initial form for the development of a large hybrid fund owing to its low fruit output, hybrid seeds, and one-year seedlings relative to pollinated flowers in case of its being used as a maternal and paternal parent.

This study was the first time in Russia to carry out a large-scale (127 samples) assessment of the diverse gene pool of black currant and red currant, the study of intervarietal polymorphism between varieties of the Ribes L. genus from the VNIISPK collection. A cluster analysis of the genetic similarity of black currant varieties (53 varieties), red currant (73 varieties) and one gooseberry variety was performed using 14 SSR markers. Based on the data obtained, a dendrogram was built, in which a number of clusters with high bootstrap support (BS, %) were distinguished. At BS>50%, the coefficients of pairwise genetic similarity between varieties varied from 0.4 to 0.91. The studied representatives of the Ribes genus merged into two main clusters of red currant and black currant. The blackcurrant cluster was joined by gooseberries. The SSR analysis method allows to reveal broad perspectives in the field of identifying varieties affiliation to species.