Resistance breeding in apple has a long tradition at the Institute of Fruit Breeding now Julius K... more Resistance breeding in apple has a long tradition at the Institute of Fruit Breeding now Julius Kuehn-institute in Dresden-Pillnitz. The breeding was aimed at the production of multiple resistance cultivars to allow a more sustainable and environmentally friendly production of apple. In the last decades a series of resistant cultivars (Re®-cultivars) bred in Dresden-Pillnitz has been released, 'Recolor' and 'Rekarda'
A major scab resistance gene initially called Vr1 was identified in the apple cultivar "Regia" de... more A major scab resistance gene initially called Vr1 was identified in the apple cultivar "Regia" derived from the Malus scab resistance source R12740-7A (Russian seedling, RS). A codominant, multiallelic sequence characterized amplified region (SCAR) marker was developed from a random amplified polymorphic DNA marker identified by bulked-segregant analysis. Additional alleles of the AD13 marker locus proved to be informative for the analysis of genetic relationships within Malus including putative relatives of RS. Separate linkage maps were created for the two families derived from crosses with "Regia". Using phenotypic data from the greenhouse scab tests, the recombination frequency between Vr1 and AD13-SCAR was between 6 and 17%. The Vr1 locus appeared to be closely linked to the Vx [Hemmat et al.
ABSTRACT The extension of the ripening season in open field production is of high economic intere... more ABSTRACT The extension of the ripening season in open field production is of high economic interest for strawberry growers. Therefore, targeted breeding for extreme early or late ripening cultivars with high yield potential is of particular interest. Thirteen strawberry cultivars were crossed in a reciprocal way without selfing, and the 144 resulting F1 populations were evaluated in a field trial over a period of two consecutive years. The data were analysed using a mixed-model approach adapted for diallel crossing designs using SAS 9.3. The variability in the crossing approach is mainly based on the general combining ability (GCA) of the cultivars (additive effects). Specific and reciprocal combining abilities (non-additive effects) appear less important. The highest GCAs for the trait Marketable Yield were found for the cultivars ‘Polka’ and ‘Yamaska’. The trait Earliness is bilateral with significantly low GCAs for early ripening in ‘Clery’ and ‘Daroyal’ and significantly high GCAs for late ripening in ‘Yamaska’ and ‘Florence’. Crosses with these cultivars are likely to deliver populations with both high yield and an extended ripening period.
ABSTRACT Progenies of ‘Schmidt's Antonovka’ (SA) have been widely used in Western breedin... more ABSTRACT Progenies of ‘Schmidt's Antonovka’ (SA) have been widely used in Western breeding programs as a source of scab resistance. The identity of SA has remained obscure, especially due to the existence of a series of ‘Antonovka’ cultivars with different origins. In this paper we show Schmidt's Antonovka to be identical to Анто́новка обыкновенный or ‘Common Antonovka’ (CA), an old Russian cultivar of unknown origin, by comparing simple sequence repeat (SSR) and SNP genotyping data from several first-generation descendants of SA from two European collections and a CA accession from the germplasm collection held at VNIISPK (The All-Russian Research Institute of Horticultural Breeding, Orel, Russia). The use of CA in Russian breeding programs is also briefly reviewed.
Fire blight is the most important bacterial disease in apple (Malus×domestica) and pear (Pyrus co... more Fire blight is the most important bacterial disease in apple (Malus×domestica) and pear (Pyrus communis) production. Today, the causal bacterium Erwinia amylovora is present in many apple-and pear-growing areas. We investigated the natural resistance of the wild apple Malus×robusta 5 against E. amylovora, previously mapped to linkage group 3. With a fine-mapping approach on a population of 2,133 individuals followed by phenotyping of the recombinants from the region of interest, we developed flanking markers useful for marker-assisted selection. Open reading frames were predicted on the sequence of a BAC spanning the resistance locus. One open reading frame coded for a protein belonging to the NBS-LRR family. The in silico investigation of the structure of the candidate resistance gene against fire blight of M.×robusta 5, FB_MR5, led us hypothesize the presence of a coiled-coil region followed by an NBS and an LRR-like structure with the consensus 'LxxLx[IL]xxCxxLxxL'. The function of FB_MR5 was predicted in agreement with the decoy/guard model, that FB_MR5 monitors the transcribed RIN4_MR5, a homolog of RIN4 of Arabidopsis thaliana that could interact with the previously described effector AvrRpt2 EA of E. amylovora.
Transgenic apple plants (Malus £ domestica cv. 'Holsteiner Cox') overexpressing the Leaf Colour (... more Transgenic apple plants (Malus £ domestica cv. 'Holsteiner Cox') overexpressing the Leaf Colour (Lc) gene from maize (Zea mays) exhibit strongly increased production of anthocyanins and Xavan-3-ols (catechins, proanthocyanidins). Greenhouse plants investigated in this study exhibit altered phenotypes with regard to growth habit and resistance traits. Lc-transgenic plants show reduced size, transversal gravitropism of lateral shoots, reduced trichome development, and frequently reduced shoot diameter and abnormal leaf development with fused leaves. Such phenotypes seem to be in accordance with a direct or an indirect eVect on polar-auxin-transport in the transgenic plants. Furthermore, leaves often develop necrotic lesions resembling hypersensitive response lesions. In tests, higher resistance against Wre blight (caused by the bacterium Erwinia amylovora) and against scab (caused by the fungus Venturia inaequalis) is observed. These phenotypes are discussed with respect to the underlying altered physiology of the Lc-transgenic plants. The results are expected to be considered in apple breeding strategies.
To break the juvenile stage of apple (Malus x domestica Borkh.) we transferred the LFY gene of Ar... more To break the juvenile stage of apple (Malus x domestica Borkh.) we transferred the LFY gene of Arabidopsis into the genome of the apple cv. 'Pinova'. A total of five transgenic clones constitutively overexpressing the LFY gene were obtained. Approximately, 20 shoots of each clone were rooted and transferred to the glasshouse. No flowers were obtained on transgenic plants during the first 2 years of cultivation. Evaluation of the expression of possible LFY targets revealed that no transcripts could be detected for MdAP1-1 and MdAP1-2. MdTFL1 was unaffected. Based on the absence of the LFY core-binding sequence within promoter sequences of MdAP1-1 and MdAP1-2, it was concluded that LFY was not able to induce these genes. The LFY genes of apple were unaffected in transgenic plants and sequence alignments of the C-terminal amino acid sequence showed a high conservation of these proteins. A change in binding ability to DNA can therefore be excluded. Instead of early flowering, the transgenic plants showed an altered phenotype, which is similar to the columnar phenotype of the 'McIntosh Wijcik' mutant of apple. The transgenic plants showed shortened internodes and a significantly reduced length of the regrowing shoot. A negative correlation was observed between the length of the regrowing shoot and the LFY mRNA transcript level. Furthermore, the LFY transgenic apple plants showed an increased shoot diameter at node 20, which was positively correlated with the LFY mRNA transcript level. Based on our results, we assume an alternative role of LFY in apple.
The bacteria Erwinia amylovora, the causal agent of fire blight, infects most members of the Malo... more The bacteria Erwinia amylovora, the causal agent of fire blight, infects most members of the Maloideae including pear and apple. In this work the defense responses against this pathogen were monitored in two apple species grown in vitro, in the susceptible Malus domestica Borkh. cv. 'Idared' (later on 'Idared') and the resistant Malus x robusta (Carrière) Rehder var. persicifolia Rehder (Mrp). Our results indicate that the resistant plants might represent a less favorable environment for bacterial growth. At the same time, in these plants higher basic levels for some defense-related compounds such as salicylic acid or their activities such as the PAL enzyme activity can be found. In fire blight infected plants both the known pathways for SA synthesis as well as most of the phenylpropanoid genes examined were repressed due to disease, but apparently could be compensated by complex regulatory mechanisms. Not only the nature but also the quantity of defense-related compounds is likely to influence the outcome of plant-pathogen interactions.
To shorten the juvenile stage of apple (Malus · domestica Borkh.) the BpMADS4 gene from silver bi... more To shorten the juvenile stage of apple (Malus · domestica Borkh.) the BpMADS4 gene from silver birch (Betula pendula Roth.) was constitutively overexpressed in 25 transgenic apple clones. All clones were characterized by PCR, RT-PCR and Real Time PCR. Solitary flowers were produced on in vitro shoots of eight transgenic clones and most of them appeared to be morphologically normal. Twenty shoots of each clone were rooted and transferred to a glasshouse. Glasshouse plants of clones T1165, T1187 and T1190 developed flowers. Several plants of T1165 and T1187 started floral initiation within 3-4 months following transfer to the glasshouse. Primary flowers were solitary and in a terminal position on the main shoot. Lateral flower clusters, consisting of three to five individual flowers, were also found. Pollen vitality and tube germination of glasshouse-grown flowers were investigated, and there were no significant differences compared to pollen of nontransgenic control plants. Preliminary crosses using flowers of glasshouse plants resulted in small apple fruits. It would seem that this is the first report on in vitro flower induction in transgenic apple.
... 2003, Silfverberg-Dilworth et al. 2006). SSR marker analysis was carried out according to the... more ... 2003, Silfverberg-Dilworth et al. 2006). SSR marker analysis was carried out according to the PCR conditions described by Liebhard et al. (2002). SSR allele identification was made on a dual-laser automated DNA sequencer (model 4200L-2; LI-COR, Lincoln, NE, USA). ...
Fire blight (FB), caused by the Gram-negative bacterium Erwinia amylovora is a dangerous disease ... more Fire blight (FB), caused by the Gram-negative bacterium Erwinia amylovora is a dangerous disease on pome fruit, including apple. The FB-susceptible cultivar ÔIdaredÕ was crossed with the resistant wild species clone Malus · robusta 5. A segregating population of 146 progeny has been tested by artificial shoot inoculation for susceptibility to FB. Progeny were infected from 0% to 100% of the shoot length. To identify chromosomal regions or loci responsible for resistance to FB of Malus · robusta 5, a set of microsatellite markers (simple sequence repeat, SSRs) was chosen covering all linkage groups of apple. Up to eight different microsatellites were bulked to one mutliplex PCR using four different labels and a fifth label for a size standard. Fifty-nine microsatellite markers out of 72 SSRs were polymorphic. Fifty-four of 66 loci detected could be mapped and were useful for the detection of related resistant loci. Alleles of microsatellites Hi03d06, CH03g07 and CH03e03 originating from the resistant donor M. robusta were associated with resistance to Erwinia amylovora. Up to eighty percent of the phenotypic variation could be explained by the interval spanned by SSRs CH03g07 and CH03e03, indicating the presence of a major resistance gene. All three microsatellites are located on the distal part of linkage group 3, spanning 15 cM. The SSR marker CH03e03 can be regarded as diagnostic marker for FB resistance. Only seven progeny expressing allele b (184 bp) of CH03e03 showed blighted shoot lengths of more than 30% and only nine progeny lacking allele b showed blighted shoot lengths of <30%. By setting a threshold of 30% shoot necrosis for resistance to FB, the 146 individuals segregate into 71 susceptible and 75 resistant plants, and resistance to FB maps 9 cM away from marker CH03e03.
Fire blight is a destructive bacterial disease caused by Erwinia amylovora affecting plants in th... more Fire blight is a destructive bacterial disease caused by Erwinia amylovora affecting plants in the family Rosaceae, including apple. Host resistance to fire blight is present mainly in accessions of Malus spp. and is thought to be quantitative in this pathosystem.
Red fruit flesh is a desirable trait in apple breeding, because red-fleshed apples are a novelty ... more Red fruit flesh is a desirable trait in apple breeding, because red-fleshed apples are a novelty and therefore considered to be more attractive to consumers and contain more health beneficial compounds. The red fruit flesh coloration is based on an increased level of cyanidin 3-galactoside, an anthocyanin whose biosynthesis is regulated by the MYB-type transcription factors MdMYB10 or MdMYB110a, respectively. A repeated segment in the MdMYB10 promoter allele R6 results in a gain-of-function mutation visible as red pigmentation of fruit skin and flesh and all vegetative tissues. Red-fleshed apple genotypes containing this R6 allele belong to the type 1 red-fleshed apple, which is known to be linked to some negative traits like astringent taste and internal flesh browning disorder. In type 2 red-fleshed apples the fruit flesh coloration is not inevitably linked with skin and leaf color. This red-fleshed apple phenotype, which is a result of increased expression of MdMYB110a, seems to be more useful for breeding, but it can be found rather seldom. In the present study 357 Malus accessions of the German Malus Germplasm Collection were evaluated for red fruit flesh coloration and the presence of the MdMYB10 R1 (not mutated) and R6 promoter alleles. Among them a total of 40 accessions were identified which contain the R6 allele. 37 accessions showed a red coloration of the fruit flesh. All these accessions belong to type 1 red-fleshed apple. No type 2 red-fleshed apple could be found. Three accessions with R6 allele had non-red-fleshed apples. 312 other non-red-fleshed accessions contained only the R1 allele. Five non-red-fleshed accessions contained a new promoter allele with an unexpected size of ~1 kbp. Sequencing of this allele detected the insertion of a non-autonomous apple transposon.
In dioecious plants of hemp ( Cannabis sativa L.), males are regarded as heterogametic XY and fem... more In dioecious plants of hemp ( Cannabis sativa L.), males are regarded as heterogametic XY and females as homogametic XX, although it is difficult to discriminate the X cytologically from the Y. The Y chromosome is somewhat larger than the X. Our aim was to analyse AFLP markers on X and Y, and to use them to gain some insight into the structure of the sex chromosomes. Markers located on the sex chromosomes can be grouped into different classes, depending on the presence or absence of a fragment on the X and/or the Y. They are detected by separately analysing male and female progenies of a single cross. Five markers were found to be located on both chromosomes. A few recombinants were observed for marker pairs of this class in the male progenies. Two completely linked markers located on the Y chromosome in the male parent show a recombination rate of r = 0.25 with sex. Recombination must have occurred between the sex chromosomes in the male parent. The recombination analysis led to the conclusion that there is a pseudoautosomal region (PAR) on the sex chromosomes, allowing recombination between the X and the Y chromosome. The other regions of the sex chromosomes show only a few recombination events, for the Y as well as for the X. These results are discussed in comparison to other dioecious plants.
Zusammenfassung Im Jahr 2003 waren die Kernobstquartiere des Instituts für Obstzüchtung der Bunde... more Zusammenfassung Im Jahr 2003 waren die Kernobstquartiere des Instituts für Obstzüchtung der Bundesanstalt für Züchtungsforschung an Kulturpflanzen in Dresden-Pillnitz stark mit Feuerbrand befallen. Der Zeitraum der Feuerbrandinfektion erstreckte sich über nahezu drei Monate. Nach dem ersten Auftreten von Symptomen an Birnen am 19.05.2003 und der amtlichen Bestätigung am 26.05.2003 wurde der letzte feuerbrandpositive Apfelbaum am 11.08.2003 bonitiert und gerodet. Aufgrund
loci (QTL) and provide insight of the magnitude of QTL across different genetic backgrounds. Here... more loci (QTL) and provide insight of the magnitude of QTL across different genetic backgrounds. Here, we present an improved Bayesian multi-QTL pedigree-based approach on an outcrossing species using progenies with different (complex) genetic relationships. Different modeling assumptions were studied in the QTL analyses, i.e., the a priori expected number of QTL varied and polygenic effects were considered. The inferences include number of QTL, additive QTL effect sizes and supporting credible intervals, posterior probabilities of QTL genotypes for all individuals in the dataset, and QTL-based as well as genome-wide breeding values. All these features have been implemented in the FlexQTL ™ software. We analyzed fruit firmness in a large apple dataset that comprised 1,347 individuals forming 27 full sib families and their known ancestral pedigrees,
Resistance breeding in apple has a long tradition at the Institute of Fruit Breeding now Julius K... more Resistance breeding in apple has a long tradition at the Institute of Fruit Breeding now Julius Kuehn-institute in Dresden-Pillnitz. The breeding was aimed at the production of multiple resistance cultivars to allow a more sustainable and environmentally friendly production of apple. In the last decades a series of resistant cultivars (Re®-cultivars) bred in Dresden-Pillnitz has been released, 'Recolor' and 'Rekarda'
A major scab resistance gene initially called Vr1 was identified in the apple cultivar "Regia" de... more A major scab resistance gene initially called Vr1 was identified in the apple cultivar "Regia" derived from the Malus scab resistance source R12740-7A (Russian seedling, RS). A codominant, multiallelic sequence characterized amplified region (SCAR) marker was developed from a random amplified polymorphic DNA marker identified by bulked-segregant analysis. Additional alleles of the AD13 marker locus proved to be informative for the analysis of genetic relationships within Malus including putative relatives of RS. Separate linkage maps were created for the two families derived from crosses with "Regia". Using phenotypic data from the greenhouse scab tests, the recombination frequency between Vr1 and AD13-SCAR was between 6 and 17%. The Vr1 locus appeared to be closely linked to the Vx [Hemmat et al.
ABSTRACT The extension of the ripening season in open field production is of high economic intere... more ABSTRACT The extension of the ripening season in open field production is of high economic interest for strawberry growers. Therefore, targeted breeding for extreme early or late ripening cultivars with high yield potential is of particular interest. Thirteen strawberry cultivars were crossed in a reciprocal way without selfing, and the 144 resulting F1 populations were evaluated in a field trial over a period of two consecutive years. The data were analysed using a mixed-model approach adapted for diallel crossing designs using SAS 9.3. The variability in the crossing approach is mainly based on the general combining ability (GCA) of the cultivars (additive effects). Specific and reciprocal combining abilities (non-additive effects) appear less important. The highest GCAs for the trait Marketable Yield were found for the cultivars ‘Polka’ and ‘Yamaska’. The trait Earliness is bilateral with significantly low GCAs for early ripening in ‘Clery’ and ‘Daroyal’ and significantly high GCAs for late ripening in ‘Yamaska’ and ‘Florence’. Crosses with these cultivars are likely to deliver populations with both high yield and an extended ripening period.
ABSTRACT Progenies of ‘Schmidt&#39;s Antonovka’ (SA) have been widely used in Western breedin... more ABSTRACT Progenies of ‘Schmidt&#39;s Antonovka’ (SA) have been widely used in Western breeding programs as a source of scab resistance. The identity of SA has remained obscure, especially due to the existence of a series of ‘Antonovka’ cultivars with different origins. In this paper we show Schmidt&#39;s Antonovka to be identical to Анто́новка обыкновенный or ‘Common Antonovka’ (CA), an old Russian cultivar of unknown origin, by comparing simple sequence repeat (SSR) and SNP genotyping data from several first-generation descendants of SA from two European collections and a CA accession from the germplasm collection held at VNIISPK (The All-Russian Research Institute of Horticultural Breeding, Orel, Russia). The use of CA in Russian breeding programs is also briefly reviewed.
Fire blight is the most important bacterial disease in apple (Malus×domestica) and pear (Pyrus co... more Fire blight is the most important bacterial disease in apple (Malus×domestica) and pear (Pyrus communis) production. Today, the causal bacterium Erwinia amylovora is present in many apple-and pear-growing areas. We investigated the natural resistance of the wild apple Malus×robusta 5 against E. amylovora, previously mapped to linkage group 3. With a fine-mapping approach on a population of 2,133 individuals followed by phenotyping of the recombinants from the region of interest, we developed flanking markers useful for marker-assisted selection. Open reading frames were predicted on the sequence of a BAC spanning the resistance locus. One open reading frame coded for a protein belonging to the NBS-LRR family. The in silico investigation of the structure of the candidate resistance gene against fire blight of M.×robusta 5, FB_MR5, led us hypothesize the presence of a coiled-coil region followed by an NBS and an LRR-like structure with the consensus 'LxxLx[IL]xxCxxLxxL'. The function of FB_MR5 was predicted in agreement with the decoy/guard model, that FB_MR5 monitors the transcribed RIN4_MR5, a homolog of RIN4 of Arabidopsis thaliana that could interact with the previously described effector AvrRpt2 EA of E. amylovora.
Transgenic apple plants (Malus £ domestica cv. 'Holsteiner Cox') overexpressing the Leaf Colour (... more Transgenic apple plants (Malus £ domestica cv. 'Holsteiner Cox') overexpressing the Leaf Colour (Lc) gene from maize (Zea mays) exhibit strongly increased production of anthocyanins and Xavan-3-ols (catechins, proanthocyanidins). Greenhouse plants investigated in this study exhibit altered phenotypes with regard to growth habit and resistance traits. Lc-transgenic plants show reduced size, transversal gravitropism of lateral shoots, reduced trichome development, and frequently reduced shoot diameter and abnormal leaf development with fused leaves. Such phenotypes seem to be in accordance with a direct or an indirect eVect on polar-auxin-transport in the transgenic plants. Furthermore, leaves often develop necrotic lesions resembling hypersensitive response lesions. In tests, higher resistance against Wre blight (caused by the bacterium Erwinia amylovora) and against scab (caused by the fungus Venturia inaequalis) is observed. These phenotypes are discussed with respect to the underlying altered physiology of the Lc-transgenic plants. The results are expected to be considered in apple breeding strategies.
To break the juvenile stage of apple (Malus x domestica Borkh.) we transferred the LFY gene of Ar... more To break the juvenile stage of apple (Malus x domestica Borkh.) we transferred the LFY gene of Arabidopsis into the genome of the apple cv. &amp;amp;amp;amp;amp;amp;amp;amp;#39;Pinova&amp;amp;amp;amp;amp;amp;amp;amp;#39;. A total of five transgenic clones constitutively overexpressing the LFY gene were obtained. Approximately, 20 shoots of each clone were rooted and transferred to the glasshouse. No flowers were obtained on transgenic plants during the first 2 years of cultivation. Evaluation of the expression of possible LFY targets revealed that no transcripts could be detected for MdAP1-1 and MdAP1-2. MdTFL1 was unaffected. Based on the absence of the LFY core-binding sequence within promoter sequences of MdAP1-1 and MdAP1-2, it was concluded that LFY was not able to induce these genes. The LFY genes of apple were unaffected in transgenic plants and sequence alignments of the C-terminal amino acid sequence showed a high conservation of these proteins. A change in binding ability to DNA can therefore be excluded. Instead of early flowering, the transgenic plants showed an altered phenotype, which is similar to the columnar phenotype of the &amp;amp;amp;amp;amp;amp;amp;amp;#39;McIntosh Wijcik&amp;amp;amp;amp;amp;amp;amp;amp;#39; mutant of apple. The transgenic plants showed shortened internodes and a significantly reduced length of the regrowing shoot. A negative correlation was observed between the length of the regrowing shoot and the LFY mRNA transcript level. Furthermore, the LFY transgenic apple plants showed an increased shoot diameter at node 20, which was positively correlated with the LFY mRNA transcript level. Based on our results, we assume an alternative role of LFY in apple.
The bacteria Erwinia amylovora, the causal agent of fire blight, infects most members of the Malo... more The bacteria Erwinia amylovora, the causal agent of fire blight, infects most members of the Maloideae including pear and apple. In this work the defense responses against this pathogen were monitored in two apple species grown in vitro, in the susceptible Malus domestica Borkh. cv. 'Idared' (later on 'Idared') and the resistant Malus x robusta (Carrière) Rehder var. persicifolia Rehder (Mrp). Our results indicate that the resistant plants might represent a less favorable environment for bacterial growth. At the same time, in these plants higher basic levels for some defense-related compounds such as salicylic acid or their activities such as the PAL enzyme activity can be found. In fire blight infected plants both the known pathways for SA synthesis as well as most of the phenylpropanoid genes examined were repressed due to disease, but apparently could be compensated by complex regulatory mechanisms. Not only the nature but also the quantity of defense-related compounds is likely to influence the outcome of plant-pathogen interactions.
To shorten the juvenile stage of apple (Malus · domestica Borkh.) the BpMADS4 gene from silver bi... more To shorten the juvenile stage of apple (Malus · domestica Borkh.) the BpMADS4 gene from silver birch (Betula pendula Roth.) was constitutively overexpressed in 25 transgenic apple clones. All clones were characterized by PCR, RT-PCR and Real Time PCR. Solitary flowers were produced on in vitro shoots of eight transgenic clones and most of them appeared to be morphologically normal. Twenty shoots of each clone were rooted and transferred to a glasshouse. Glasshouse plants of clones T1165, T1187 and T1190 developed flowers. Several plants of T1165 and T1187 started floral initiation within 3-4 months following transfer to the glasshouse. Primary flowers were solitary and in a terminal position on the main shoot. Lateral flower clusters, consisting of three to five individual flowers, were also found. Pollen vitality and tube germination of glasshouse-grown flowers were investigated, and there were no significant differences compared to pollen of nontransgenic control plants. Preliminary crosses using flowers of glasshouse plants resulted in small apple fruits. It would seem that this is the first report on in vitro flower induction in transgenic apple.
... 2003, Silfverberg-Dilworth et al. 2006). SSR marker analysis was carried out according to the... more ... 2003, Silfverberg-Dilworth et al. 2006). SSR marker analysis was carried out according to the PCR conditions described by Liebhard et al. (2002). SSR allele identification was made on a dual-laser automated DNA sequencer (model 4200L-2; LI-COR, Lincoln, NE, USA). ...
Fire blight (FB), caused by the Gram-negative bacterium Erwinia amylovora is a dangerous disease ... more Fire blight (FB), caused by the Gram-negative bacterium Erwinia amylovora is a dangerous disease on pome fruit, including apple. The FB-susceptible cultivar ÔIdaredÕ was crossed with the resistant wild species clone Malus · robusta 5. A segregating population of 146 progeny has been tested by artificial shoot inoculation for susceptibility to FB. Progeny were infected from 0% to 100% of the shoot length. To identify chromosomal regions or loci responsible for resistance to FB of Malus · robusta 5, a set of microsatellite markers (simple sequence repeat, SSRs) was chosen covering all linkage groups of apple. Up to eight different microsatellites were bulked to one mutliplex PCR using four different labels and a fifth label for a size standard. Fifty-nine microsatellite markers out of 72 SSRs were polymorphic. Fifty-four of 66 loci detected could be mapped and were useful for the detection of related resistant loci. Alleles of microsatellites Hi03d06, CH03g07 and CH03e03 originating from the resistant donor M. robusta were associated with resistance to Erwinia amylovora. Up to eighty percent of the phenotypic variation could be explained by the interval spanned by SSRs CH03g07 and CH03e03, indicating the presence of a major resistance gene. All three microsatellites are located on the distal part of linkage group 3, spanning 15 cM. The SSR marker CH03e03 can be regarded as diagnostic marker for FB resistance. Only seven progeny expressing allele b (184 bp) of CH03e03 showed blighted shoot lengths of more than 30% and only nine progeny lacking allele b showed blighted shoot lengths of <30%. By setting a threshold of 30% shoot necrosis for resistance to FB, the 146 individuals segregate into 71 susceptible and 75 resistant plants, and resistance to FB maps 9 cM away from marker CH03e03.
Fire blight is a destructive bacterial disease caused by Erwinia amylovora affecting plants in th... more Fire blight is a destructive bacterial disease caused by Erwinia amylovora affecting plants in the family Rosaceae, including apple. Host resistance to fire blight is present mainly in accessions of Malus spp. and is thought to be quantitative in this pathosystem.
Red fruit flesh is a desirable trait in apple breeding, because red-fleshed apples are a novelty ... more Red fruit flesh is a desirable trait in apple breeding, because red-fleshed apples are a novelty and therefore considered to be more attractive to consumers and contain more health beneficial compounds. The red fruit flesh coloration is based on an increased level of cyanidin 3-galactoside, an anthocyanin whose biosynthesis is regulated by the MYB-type transcription factors MdMYB10 or MdMYB110a, respectively. A repeated segment in the MdMYB10 promoter allele R6 results in a gain-of-function mutation visible as red pigmentation of fruit skin and flesh and all vegetative tissues. Red-fleshed apple genotypes containing this R6 allele belong to the type 1 red-fleshed apple, which is known to be linked to some negative traits like astringent taste and internal flesh browning disorder. In type 2 red-fleshed apples the fruit flesh coloration is not inevitably linked with skin and leaf color. This red-fleshed apple phenotype, which is a result of increased expression of MdMYB110a, seems to be more useful for breeding, but it can be found rather seldom. In the present study 357 Malus accessions of the German Malus Germplasm Collection were evaluated for red fruit flesh coloration and the presence of the MdMYB10 R1 (not mutated) and R6 promoter alleles. Among them a total of 40 accessions were identified which contain the R6 allele. 37 accessions showed a red coloration of the fruit flesh. All these accessions belong to type 1 red-fleshed apple. No type 2 red-fleshed apple could be found. Three accessions with R6 allele had non-red-fleshed apples. 312 other non-red-fleshed accessions contained only the R1 allele. Five non-red-fleshed accessions contained a new promoter allele with an unexpected size of ~1 kbp. Sequencing of this allele detected the insertion of a non-autonomous apple transposon.
In dioecious plants of hemp ( Cannabis sativa L.), males are regarded as heterogametic XY and fem... more In dioecious plants of hemp ( Cannabis sativa L.), males are regarded as heterogametic XY and females as homogametic XX, although it is difficult to discriminate the X cytologically from the Y. The Y chromosome is somewhat larger than the X. Our aim was to analyse AFLP markers on X and Y, and to use them to gain some insight into the structure of the sex chromosomes. Markers located on the sex chromosomes can be grouped into different classes, depending on the presence or absence of a fragment on the X and/or the Y. They are detected by separately analysing male and female progenies of a single cross. Five markers were found to be located on both chromosomes. A few recombinants were observed for marker pairs of this class in the male progenies. Two completely linked markers located on the Y chromosome in the male parent show a recombination rate of r = 0.25 with sex. Recombination must have occurred between the sex chromosomes in the male parent. The recombination analysis led to the conclusion that there is a pseudoautosomal region (PAR) on the sex chromosomes, allowing recombination between the X and the Y chromosome. The other regions of the sex chromosomes show only a few recombination events, for the Y as well as for the X. These results are discussed in comparison to other dioecious plants.
Zusammenfassung Im Jahr 2003 waren die Kernobstquartiere des Instituts für Obstzüchtung der Bunde... more Zusammenfassung Im Jahr 2003 waren die Kernobstquartiere des Instituts für Obstzüchtung der Bundesanstalt für Züchtungsforschung an Kulturpflanzen in Dresden-Pillnitz stark mit Feuerbrand befallen. Der Zeitraum der Feuerbrandinfektion erstreckte sich über nahezu drei Monate. Nach dem ersten Auftreten von Symptomen an Birnen am 19.05.2003 und der amtlichen Bestätigung am 26.05.2003 wurde der letzte feuerbrandpositive Apfelbaum am 11.08.2003 bonitiert und gerodet. Aufgrund
loci (QTL) and provide insight of the magnitude of QTL across different genetic backgrounds. Here... more loci (QTL) and provide insight of the magnitude of QTL across different genetic backgrounds. Here, we present an improved Bayesian multi-QTL pedigree-based approach on an outcrossing species using progenies with different (complex) genetic relationships. Different modeling assumptions were studied in the QTL analyses, i.e., the a priori expected number of QTL varied and polygenic effects were considered. The inferences include number of QTL, additive QTL effect sizes and supporting credible intervals, posterior probabilities of QTL genotypes for all individuals in the dataset, and QTL-based as well as genome-wide breeding values. All these features have been implemented in the FlexQTL ™ software. We analyzed fruit firmness in a large apple dataset that comprised 1,347 individuals forming 27 full sib families and their known ancestral pedigrees,
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Papers by Andreas Peil