Phenotypic and molecular characterization of 18 Bulgarian newly bred grapevine varieties in relation to their resistance to downy mildew

<p>Eighteen Bulgarian newly bred grapevine varieties obtained by interspecific crossing were analysed through microsatellite markers in order to determine their genetic identity as well as the presence of resistance-related alleles linked to <i>Rpv3</i>, <i>Rpv10</i> and <i>Rpv12</i> loci. The levels of resistance of the investigated cultivars to downy mildew were assessed by leaf disk assay and were scored according to OIV descriptor 452. Seven isolates of <i>Plasmopara viticola</i> collected in different regions of Bulgaria were characterized and discriminated with seven microsatellite markers and were used in the assays. Analysis of variance showed significant differences in resistance to downy mildew among the analysed varieties. A clear correlation between the presence of particular <i>Rpvs</i> and the level of resistance was determined. Five cultivars, ‘Droujba’, ‘Garant’ and ‘Plevenska rosa’ harbouring <i>Rpv3</i> and <i>Rpv12</i>, ‘Kajlashki rubin’ harbouring <i>Rpv12</i> and ‘Slava’, <i>Rpv10</i> and <i>Rpv3</i>, showed high level of resistance with mean OIV452 values ranging from 6.5 to 8.25 over all seven <i>P. viticola</i> isolates. The level of resistance of the remaining 14 cultivars, which carry only <i>Rpv</i>3 inherited from cultivar Villard Blanc, was found to vary significantly among the isolates with mean OIV452 values between 1.75 and 4.8 over all used <i>P. viticola</i> isolates. The results obtained in this study favoured five genotypes remarkable for their high resistance to downy mildew and very good quality of grape and wine. These varieties represent a valuable material for pyramiding of resistance through marker-assisted selection.</p

Genetic diversity and relationships of indigenous and newly bred Bulgarian grape cultivars assessed by nuclear and chloroplast markers

Aim: Assessment of the genetic diversity and relationships in a group of 31 Bulgarian grape accessions through microsatellite markers. Methods and results: Thirty-one accessions, including 20 old rare local and 11 newly bred varieties were characterized through 13 nuclear and 5 chloroplast microsatellite loci. The genetic diversity (0.81±0.01) obtained for the investigated group of cultivars was comparable to those reported for other grapevine germplasms. The low PI value (1.0x10-16) allowed proper genetic identification and determination of synonyms. Microsatellite analysis of the 31 accessions resulted in 26 unique genotypes and 2 groups of synonyms. Four cases of supposed synonymy with local Bulgarian and foreign cultivars were rejected. Three chlorotypes, B, C and D, were defined among the studied cultivars, with a prevalence of chlorotype C (62%). Conclusion: The high genetic diversity found in the set of old rare grapevines demonstrated their importance as a rich source of alleles for breeding. The pattern of chlorotype distribution observed among local varieties confirmed the previous results and supports the hypothesis of an Eastern origin of local Bulgarian cultivars. Significance and impact of the study: The obtained results provide an important support for the preservation of grape biodiversity in Bulgaria as well as for the clarification of genetic relationships between local and foreign cultivars