1,721,026 research outputs found
Development of reliable PCR markers for the selection of the Vf gene conferring scab resistance in apple
No full textEarly selection of scab-resistant apple seedlings can be enhanced by the use of markers tightly linked to the Vf resistance gene. Two sequence characterized amplified regions (SCAR) markers have been obtained from previously described random amplified polymorphic DNA (RAPD) markers. AL07-SCAR is a codominant marker, while AM19-SCAR is dominant, as is the RAPD from which it was derived. A highly detailed map in the vicinity of the Vf gene was built through the cumulative analysis of about 600 seedlings from six different controlled crosses. The usefulness of these and other SCAR markers will be discussed in relation to combining the traditional phenotypic selection with MAS. The availability of two codominant, tightly linked markers flanking both sides of the resistance gene (AL07-SCAR and M18-CAPS) also makes it easy to identify the seedlings homozygous for the resistance gene
Molecular markers applied to apple breeding: analysis of oligogenic and single gene resistances
No full textThe use of molecular markers can dramatically improve apple breeding by increasing selection efficiency. We show two examples of how DNA markers have been successfully applied to prove that the resistance gene present in the cultivar 'Nova Easygro' (said to be Vr), is tightly linked to V f and is most probably Vf itself. We were able to detect homozygous resistant plants and showed that those plants are on average more resistant than the heterozygous ones. In a population obtained by crossing a powdery mildew resistant selection (A679-2) and a susceptible one ('Iduna') we studied the resistance to powdery mildew introgressed from Malus zumi (Pl 2). Genetic linkage maps of the two parental plants were constructed. By analysing Quantitative Trait Loci (QTL) we were able to detect two major genomic regions containing genes controlling the resistance. Several other minor regions have been detected both in the resistant and in the susceptible parents. The analysis of a larger sample and repeated observations over several years will enable a more precise localisation of the QTLs and evaluation of the importance of the genomic regions containing putative loci controlling powdery mildew resistance
Creating a saturated reference map for the apple (Malus x domestica Borkh.) genome
No full textThe availability of a high quality linkage map is essential for the detection and the analysis of quantitative traits. Such a map should cover a significant part of the genome, should be densely populated with markers, and in order to gain the maximum advantage should be transferable to populations or cultivars other than the ones on which it has been constructed. An apple genetic linkage map has been constructed on the basis of a segregating population of the cross between the cultivars Fiesta and Discovery. A total of 840 molecular markers, 475 AFLPs, 235 RAPDs, 129 SSRs and 1 SCAR, were used for the two parental maps constructed with JoinMap and spanning 1,140 cM and 1,450 cM, respectively. Large numbers of codominant markers, like SSRs, enable a rapid transfer of the map to other populations or cultivars, allowing the investigation of any chosen trait in another genetic background. This map is currently the most advanced linkage map in apple with regard to genome coverage and marker density. It represents an ideal starting point for future mapping projects in Malus since the stable and transferable SSR frame of the map can be saturated quickly with dominant AFLP markers
Global climate change and sustainable management of agriculture in a highly developed mountain
No full textDNA markers linked to Malus floribunda 821 scab resistance
No full textBreeding resistant apple plants is an alternative way to control fungal pathogens reducing the environmental impact due to the use of pesticides. The breeding of apple cultivars resistant to Venturia inaequalis could be much improved by marker-assisted selection. A molecular marker closely linked to the resistance locus called Vf could replace selection based on infection studies. To find such molecular markers, DNA of progenies from crossings of a resistant and a susceptible apple tree was subject to bulked segregant analysis. Two markers were found with a genetic distance of 10.6% and 19.7% recombination frequency to the Vf locus
Venturia inaequalis resistance in apple
No full textApple scab caused by Venturia inaequalis has evoked the interest for quite different reasons of scientists, agronomists, producers and consumers since over a century. Consumers select spotless apples, producers want to avoid damage, agronomists are asked to develop and implement control measures mostly based on fungicides, scientists are challenged to find cheaper and less questioned control measures. Under these premises a high number of publications have appeared dealing with almost all aspects of the interaction V. inaequalis-Malus. This review considers the advances of the past 10 years due to new genetic tools. It tries to reevaluate and value earlier works. The complex genetic of scab resistance in Malus is viewed in the context of single resistance genes, QTLs and functional interactions at molecular level. Consequences for breeding and for the creation of genetically modified apples are discussed
Molecular selection in apple for resistance to scab caused by Venturia inaequalis
No full textLarge-scale marker-assisted selection requires highly reproducible, consistent and simple markers. The use of genetic markers is important in woody plant breeding in general, and in apple in particular, because of the high level of heterozygosity present in Malus species. We present here the transformation of two RAPD markers, which we found previously to be linked to the major scab resistance gene Vf, into more reliable and reproducible markers that can be applied directly to apple breeding. We give an example of how the use of such markers can speed up selection for the introduction of scab resistance genes into the same plant, reducing labour and avoiding time- consuming test crosses. We discuss the nature and relationship of the scab resistance gene Vf to the one present in Nova Easygro, thought to be Vr
Marker-assisted selection in apple breeding
No full textApple breeding is aimed at creating varieties with high fruit quality, regular and high yields and durable disease and pest resistance. Traditional breeding is time and labour consuming. DNA markers for traits related to fruit quality, productivity and resistances will allow early and precise selection for desired characters. Within the framework of an EU apple genome project and the Swiss Science Foundation priority programme biotechnology we have focussed mainly on molecular markers related to scab and mildew resistance. CAPS and SCAR-markers were developed which allow to determine the allelic status of the Vf locus coding for scab resistance. Progeny plants obtained from crosses with two Vf-resistant parents were used. Markers for the Vbj scab resistance originating from Malus baccata jackii have been developed and will allow the combination of Vf and Vbj resistance in the same genotype in order to increase durability of resistance. The segregation for mildew resistance in the progeny Iduna x A 679-2 comprising 400 individuals was assessed. Quantitative trait loci (QTL)-analysis using the nonparametric Kruskal-Wallis test was performed. Major QTLs controlling mildew resistance were detected in the A 679-2 genome. A linkage map was constructed using a random subpopulation of 189 individuals of Iduna x A 679-2 using random amplified polymorphic DNA. The linkage map of A 679-2 contains 142 RAPD-markers and 9 microsatellites arranged in 15 linkage groups. Routine application of marker-assisted selection for scab resistance is being investigated also for economical feasibility
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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