Short description
(English)
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Xanthomonas arboricola pv. pruni is a quarantine pathogen that poses a potentially serious threat to stone fruit production in Switzerland. Current control options using copper bactericides are unsustainable due to common pathogen resistance devel-opment and environmental concerns. Host disease resistance offers the most prom-ise for long-term disease management. Unfortunately, most commercial varieties in Europe are highly susceptible to bacterial spot. This project aims to identify resis-tance QTLs in apricot and develop molecular markers that will stream-line the breed-ing process. A genetic map of the cross ‘Hatostar’ X ‘Rouge de Mauve’ will be pre-pared and used for QTL analysis along with phenotypic data (relative disease sus-ceptibility of progeny). SSR markers will be developed for resistance QTLs and vali-dated in other apricot backgrounds, and for application in Smart-breeding (marker-assisted selection MAS). During this process a standardized resistance screening protocol for X. arboricola pv. pruni will be drafted as part of COST873.
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Partners and International Organizations
(English)
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AT, BE, BG, CH, CZ, DE, DK, EL, ES, FR, HU, IL, IT, LT, LV, NL, NO, PL, PT, RO, RS, SI, TR, UK
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Abstract
(English)
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Bacterial spot of stone fruits, caused by the quarantine (Switzerland/EU) pathogen Xanthomonas arboricola pv. pruni (Xap), is a major threat to Prunus crops including peach, apricot, plum and almonds. Current control options (copper sprays and the use of antibiotics) are unsustainable. The use of resistant or at least less susceptible cultivars should become an important piece of the management of the disease. Until now only few peach, apricot and plum cultivars have been studied for their resistance to the pathogen. As no complete resistance has been found it is thought that Xap resistance is quantitative. Our project aims at identifying quantitative trait loci (QTLs) involved in Xap resistance in apricot, and at developing molecular markers that can be used for marker assisted selection in the view of breeding new cultivars with increased disease resistance. In 2010, the apricot population deriving from the cross 'Harostar' x 'Rouge de Mauves' was inoculated with a mix of Xap strains using a technique that was previously developed in preliminary experiments. Together with the constructed genetic map this allowed the identification of two QTLs in the parent 'Rouge de Mauves' on linkage groups (LG) 3 and 5. In depth analysis of the phenotypic data obtained in 2010 together with the phenotypic data obtained in 2011 by the re-inoculation of the same progeny with a different mix of strains allowed the confirmation of the major QTL for Xap resistance on LG5. The other minor QTL on LG3 was not confirmed. With the demonstration of the stability of this region for the control of the disease all six tasks of the project have been successfully completed and a first set of molecular markers suitable to start the improvement of the resistance level of apricots to Xap are available to the breeders. In 2010 the peach genome has been sequenced and the annotated sequence has been released (i.e. is public available). This milestone of the Prunus research made transcriptome analysis in these species possible. Currently, we are performing a transcriptome analysis in peach upon inoculation with Xap. This analysis will permit to identify genes involved in Xap resistance. Due to the high level of syntheny between peach and apricot the experiment may help understanding the resistance mechanism of the QTL found on linkage group 5. Finally, the genetic map and the progeny of the cross 'Harostar' x 'Rouge de Mauves' has been further used to start the identification of QTLs for agronomical and fruit quality traits. QTLs for flowering time, ground color and sugar content, have been identified. However these need to be confirmed in the next years.
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