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Molecular genetic analysis revealed a polymorphism for the Md Exp7 gene that controls the bio synthesis of expansin in wild species of the genus Malus. Eight allelic forms of the gene were identified, four of which were unique. The regularities in the allele distribution in 37 genotypes were found to be in accor dance with their systematic positions. The trait was found to be broadly diverse both among the sections of the genus and within a particular section. Variants of the gene were identified in representatives of one species.

Background. Monogenic scab resistance is an important trait of apple, useful to plant breeders. DNA markers provide a possibility to differentiate apple cultivars according to individual resistance determinants with high reliability and identify promising genotypes. The present study shows the results of the molecular genetic analysis of apple varieties, targeted at the Rvi2, Rvi4, Rvi6 and Rvi8 monogenic scab resistance loci.Materials and methods. Biological material was represented by apple cultivars of different environmental and geographical origin. Total genomic DNA was extracted from fresh leaves using CTAB methods according to the DArT protocols. The Rvi6 gene was identified with two markers, VfC (STS) and AL07 (SCAR). The presence of the Rvi4 gene was detected with the multiallelic SCAR marker AD13. The Rvi2 and Rvi8 genes were diagnosed with the SCAR marker OPL19.Results and conclusion. The Rvi6 gene was identified in 54.4% of genotypes, of which 91.9% were heterozygous, and 8.1% (cvs. ‘Svezhest’, ‘Freedom’ and ‘GoldRush’) homozygous dominant for this locus. The marker AD13-SCAR was detected in 25.0% of the studied forms (the putative genotype for the resistance gene is Rvi4Rvi4 or Rvi4rvi4). The marker OPL19-SCAR (Rvi2 and Rvi8 genes) was present in 73.5% of the analyzed forms. At least one of the studied molecular markers was present in the genome of 86.8% of genotypes. The appletree cultivars ‘Kandil Orlovsky’, ‘Krasulya’, ‘Sozvezdiye’, ‘Galarina’, ‘Priam’, ‘Redfree’ and ‘Witos’ are characterized by the combination of markers VfC, AL07-SCAR, AD13-SCAR and OPL19-SCAR in one genotype (the putative genotype for the resistance genes is Rvi2(Rvi8)Rvi4Rvi6rvi6). Cvs. ‘Antonovka zimnyaya’, ‘Antonovka krasnaya’, ‘Berkutovskoye’, ‘Geyzer’, ‘Pamyati Nesterova’, ‘Renet Simirenko’, ‘Terentyevka’, ‘Golden Delicious’, and ‘Telemon’ presumably have a homozygous recessive genotype for the studied resistance loci.

Powdery mildew (Podosphaera leucotricha (Ell. E tEv.) Salm.) – is one of the most widespread apple diseases in world. Identification of forms, carrying resistance genes, is an important stage in breeding programs aimed at obtaining powdery mildew resistant apple varieties. Diagnostic DNA markers of target genes will increase reliability of identification and efficiency of apple breeding for the creation of resistant genotypes. The purpose of this study was molecular genetic testing of wild species of genus Malus Mill. According to Pl-1, Pl-w and Pl-d powdery mildew resistance genes for revealing polymorphism of the studied loci and identification of valuable genotypes for breeding. The study subjects were the wild species of genus Malus Mill. of different ecological and geographic origin. The Pl-1 gene was identified using AT20-SCAR marker, Pl-w gene - EM M02 marker, Pl-d gene - EM DM01 marker. AT20-SCAR marker (Pl-1 gene) was identified in 37.3 % of genotypes. EM M02 marker (Pl-w gene) was detected in 16.4 % of the studied forms. EM DM01 marker (Pl-d gene) is present in 10.4 % of the analyzed forms. At least one of the studied molecular markers is present in the genome of 52.2 % of apple wild species. The Pl-1 gene in apple wild species is most spread in Baccatae series, the Pl-w gene - in Baccatae and Sieboldinae series, the Pl-d gene - in Orientalis series. Wild species M. baccata 2319, M. mandshurica 41947, M. sachalinensis 85, M. sachalinensis 97, M. purpurea v. pendula 2396 are characterized by combination of Pl-1 and Pl-w genes; M. turkmenorum 13283 and M. turkmenorum 29 421 - Pl-1 and Pl-d genes; M. denticulata 29416 - Pl-w and Pl-d genes, which allows to recommend them as promising complex sources of high powdery mildew resistance for breeding.

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The Michurinsk Department of the Vavilov Society of Geneticists and Breeding Scientists (VOGiS) was formed in 1966 after the constituent congress of VOGiS and nowadays includes 54 members. The scientists are engaged in 4 scientific institutions affiliated with FASO of Russia. The paper presents investigations of the individual genetics of leading fruit crops (pear, cherry, apple), identified genes, regularities of inheriting resistance to low temperatures, the most harmful diseases and several characters responsible for fruit quality. Some genes were identified for the first time. These are genes regulating Coccomyces hiemalis Higg. resistance (A), retarded growth habit in cherry (O 2), astringency (Ta) and juiciness (Su) of fruit in pear. On the base of hybridological analysis and DNA marking, genotypes were identified. These genotypes carry target alleles of the following genes: columnar growth habit (Co) in apple, dwarf trait (PcDw) in pear, retardant growth (O 2) in cherry. It was found that the markers C18470-25831, Mdo.chr 10.12, Co04R12 do not always show robust results for screening of young apple seedlings with columnar growth habit (Co) because they are identified as non-columnar forms. The primer pairs of 29f1 и jwi1r are the most robust ones for identification of columnar genotypes. These primers amplify specific PCR product of 586 bp (5'CR). On the basis of molecular-genetic analysis of apple initial forms and hybrid seedlings, there were identified targeted alleles of monogenic scab resistance genes including dominant homozygous genotype (Rvi6Rvi6) and also alleles of genes involved in the control of the biosynthesis of ethylene (Md-ACS1 and Md-ACO1) and expansin (Md-Exp7) controlling fruit long shelf life and pulp firmness.

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