99 research outputs found
Quantitative trait loci affecting pathogen resistance and ripening of grapevines
Grapevines (Vitis vinifera L.) form the basis of
viticulture, and are susceptible to diseases such as downy
mildew (Plasmopara viticola) and powdery mildew (Erysiphe necator). Therefore, successful viticulture programs
require the use of pesticides. Breeding for resistance is the
only eco-friendly solution. Marker-assisted selection is currently widely used for grapevine breeding. Consequently,
traits of interest must be tagged with molecular markers
linked to quantitative trait loci (QTL). We herein present
our findings regarding genetic mapping and QTL analysis of resistance to downy and powdery mildew diseases
in the progenies of the GF.GA-47-42 (‘Bacchus’ × ‘Seyval’) × ‘Villard blanc’ cross. Simple sequence repeats and
single nucleotide polymorphisms of 151 individuals were
analyzed. A map consisting of 543 loci was screened for
QTL analyses based on phenotypic variations observed in
plants grown in the field or under controlled conditions. A
major QTL for downy mildew resistance was detected on
chromosome 18. For powdery mildew resistance, a QTL was identified on chromosome 15. This QTL was replaced
by a novel QTL on chromosome 18 in 2003 (abnormally
high temperatures) and 2004. Subsequently, both QTLs
functioned together. Additionally, variations in the timing of the onset of veraison, which is a crucial step during
grape ripening, were studied to identify genomic regions
affecting this trait. A major QTL was detected on linkage
group 16, which was supplemented by a minor QTL on
linkage group 18. This study provides useful information
regarding novel QTL-linked markers relevant for the breeding of disease-resistant grapevines adapted to current climatic conditions
Introgression reshapes recombination distribution in grapevine interspecific hybrids
In grapevine interspecific hybrids, meiotic recombination is suppressed in homeologous regions and enhanced in homologous regions of recombined chromosomes, whereas crossover rate remains unchanged when chromosome pairs are entirely homeologous
Using a limited mapping strategy to identify major QTLs for resistance to grapevine powdery mildew (Erysiphe necator) and their use in marker-assisted breeding
A limited genetic mapping strategy based on simple sequence repeat (SSR) marker data was used with five grape populations segregating for powdery mildew (Erysiphe necator) resistance in an effort to develop genetic markers from multiple sources and enable the pyramiding of resistance loci. Three populations derived their resistance from Muscadinia rotundifolia ‘Magnolia’. The first population (06708) had 97 progeny and was screened with 137 SSR markers from seven chromosomes (4, 7, 9, 12, 13, 15, and 18) that have been reported to be associated with powdery or downy mildew resistance. A genetic map was constructed using the pseudo-testcross strategy and QTL analysis was carried out. Only markers from chromosome 13 and 18 were mapped in the second (04327) and third (06712) populations, which had 47 and 80 progeny, respectively. Significant QTLs for powdery mildew resistance with overlapping genomic regions were identified for different tissue types (leaf, stem, rachis, and berry) on chromosome 18, which distinguishes the resistance in ‘Magnolia’ from that present in other accessions of M. rotundifolia and controlled by the Run1 gene on chromosome 12. The ‘Magnolia’ resistance locus was termed as Run2.1. Powdery mildew resistance was also mapped in a fourth population (08391), which had 255 progeny and resistance from M. rotundifolia ‘Trayshed’. A locus accounting for 50% of the phenotypic variation mapped to chromosome 18 and was named Run2.2. This locus overlapped the region found in the ‘Magnolia’-based populations, but the allele sizes of the flanking markers were different. ‘Trayshed’ and ‘Magnolia’ shared at least one allele for 68% of the tested markers, but alleles of the other 32% of the markers were not shared indicating that the two M. rotundifolia selections were very different. The last population, 08306 with 42 progeny, derived its resistance from a selection Vitis romanetii C166-043. Genetic mapping discovered a major powdery mildew resistance locus termed Ren4 on chromosome 18, which explained 70% of the phenotypic variation in the same region of chromosome 18 found in the two M. rotundifolia resistant accessions. The mapping results indicate that powdery mildew resistance genes from different backgrounds reside on chromosome 18, and that genetic markers can be used as a powerful tool to pyramid these loci and other powdery mildew resistance loci into a single line
Use of SSR and retrotransposon-based markers to interpret the population structure of native grapevines from Southern Italy
Native grapevines are the quintessential ele- ments of Southern Italy winemaking, and genomic char- acterization plays a role of primary importance for preservation and sustainable use of these unexploited genetic resources. Among the various molecular techniques available, SSR and retrotransposons-based markers result to be the most valuable for cultivars and biotypes distinc- tiveness. A total of 62 accessions including 38 local grape cultivars were analyzed with 30 SSR, four REMAP and one IRAP markers to assess their genetic diversity and obtain a complete genomic profiling. The use of VrZAG79, VrZAG112, VVS2, VVMD25 and VVMD5 combined with retrotransposon-based markers proved to be the most dis- criminating and polymorphic markers for the rapid and unambiguous identification of minority grapevines from Campania region, which is considered one of the most appreciated Italian districts for wine production. Results revealed 58 SSR marker-specific alleles, 22 genotype- specific SSR alleles, and four REMAP and IRAP private bands. Cases of synonymy and homonymy were discov- ered. In conclusion, we provided evidences that the inte- grating SSR and retrotransposon-based markers is an effective strategy to assess the genetic diversity of autochthonous grapes, allowing their easy identification
Identification of two novel powdery mildew resistance loci, Ren6 and Ren7, from the wild Chinese grape species Vitis piasezkii
Descriptive statistics of the phenotypic scores within the base mapping population 11-373. Powdery mildew symptoms in the field were evaluated in two subsequent years. Greenhouse, in vitro experiments and the qPCR-based molecular assay were carried out with three to four biological replicates of each seedling plant in 2014. (DOCX 14ย�kb
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