Relationship of Pruning and Growth Morphology with Hormone Ratios in Shoots of Pillar and Standard Peach Trees

Genotype and cultural management determine the shape of peach [Prunus persica (L.) Batch] tree canopies in orchards. Not well understood, however, is the relationship between terminal growth, lateral branching, and shoot hormone levels that can fundamentally affect tree canopy development. In this experiment, two peach cultivars with widely differing growth habits (Pillar, KV930479 and Standard, ‘Harrow Beauty’) were budded on ‘Lovell’ rootstock, planted in the field in 1998, and characterized for shoot morphology and hormone concentrations in 2002 and 2003 (the fourth and fifth leaf, respectively). Auxin (indole-3-acetic acid) and cytokinins (largely trans-zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine) were measured in shoot tips (2002) and current-year shoots (2003) using mass spectrometry. In 2002, Pillar trees had less sylleptic branching, more upright growth, and higher auxin and auxin-to-cytokinin ratios than Standard trees. In Pillar trees in 2003, auxin concentrations and shoot growth were highest in current year shoots; in pruned trees, only auxin levels increased. Peach tree growth habits may be the result of altered hormone metabolism. Growth forms leading to superior production efficiency may be developed by selection based on specific target hormone concentrations and ratios.     

Chromosome landing at the Mla locus in barley (Hordeum vulgare L.) by means of high-resolution mapping with AFLP markers

 The complex Mla locus of barley determines resistance to the powdery mildew pathogen Erysiphe graminis f. sp. hordei. With a view towards gene isolation, a population consisting of 950 F₂ individuals derived from a cross between the near-isogenic lines ‘P01’ (Mla1) and ‘P10’ (Mla12) was used to construct a high-resolution map of the Mla region. A fluorescence-based AFLP technique and bulked segregant analysis were applied to screen for polymorphic, tightly linked AFLP markers. Three AFLP markers were selected as suitable for a chromosome-landing strategy. One of these AFLP markers and a closely linked RFLP marker were converted into sequence-specific PCR markers. PCR-based screening of approximately 70 000 yeast artificial chromosome (YAC) clones revealed three identical YACs harbouring the Mla locus. Terminal insert sequences were obtained using inverse PCR. The derived STS marker from the right YAC end-clone was mapped distal to the Mla locus. Received: 17 July 1998 / Accepted: 9 August 1998     

A reciprocal translocation between ’Garfi’ almond and ’Nemared’ peach

A map with 51 markers (46 RFLPs and five isozymes) was constructed using an interspecific F₂ population between ’Garfi’ almond (Prunus amygdalus Batsch.) and ’Nemared’ peach [Prunus persica (L.) Batsch.]. This map was developed by selecting markers covering most of the distance of the eight linkage groups from previously constructed Prunus maps. The markers studied in this population mapped to seven linkage groups instead of the eight expected in Prunus. Markers belonging to groups 6 and 8 in previous maps formed a single group in the ’Garfi’×’Nemared’ F₂ and several marker pairs placed in different groups in other maps exhibited tight linkages. The study of pollen fertility and chromosome behavior during meiosis in the F₁ generation allowed us to confirm the hypothesis that a reciprocal translocation exists between ’Garfi’ and ’Nemared’. Based on independent evidence of linkage between markers and pollen fertility data in the F₂ population, we concluded that the breakpoint of the reciprocal translocation was placed between markers AC50 and AG26A in group 6 and between markers AG112A and FG230A in group 8. Received: 28 June 2000 / Accepted: 17 October 2000     

Rust mite resistance in apple assessed by quantitative trait loci analysis

The aim of this study was to assess the genetic basis of rust mite (Aculus schlechtendali) resistance in apple (Malus × domestica). A. schlechtendali infestation of apple trees has increased as a consequence of reduced side effects of modern fungicides on rust mites. An analysis of quantitative trait loci (QTLs) was carried out using linkage map data available for F₁ progeny plants of the cultivars ‘Fiesta’ × ‘Discovery’. Apple trees representing 160 different genotypes were surveyed for rust mite infestation, each at three different sites in two consecutive years. The distribution of rust mites on the individual apple genotypes was aggregated and significantly affected by apple genotype and site. We identified two QTLs for A. schlechtendali resistance on linkage group 7 of ‘Fiesta’. The AFLP marker E35M42-0146 (20.2 cM) and the RAPD marker AE10-400 (45.8 cM) were closest positioned to the QTLs and explained between 11.0% and 16.6% of the phenotypic variability. Additionally, putative QTLs on the ‘Discovery’ chromosomes 4, 5 and 8 were detected. The SSR marker Hi03a10 identified to be associated to one of the QTLs (AFLP marker E35M42-0146) was traced back in the ‘Fiesta’ pedigree to the apple cultivar ‘Wagener’. This marker may facilitate the breeding of resistant apple cultivars by marker assisted selection. Furthermore, the genetic background of rust mite resistance in existing cultivars can be evaluated by testing them for the identified SSR marker. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Construction of an integrated pepper map using RFLP,SSR, CAPS,AFLP, WRKY,rRAMP, and BAC end sequences

Map-based cloning to find genes of interest, markerassisted selection (MAS), and marker-assisted breeding (MAB) all require good genetic maps with high reproducible markers. For map construction as well as chromosome assignment, development of single copy PCR-based markers and map integration process are necessary. In this study, the 132 markers (57 STS from BAC-end sequences, 13 STS from RFLP, and 62 SSR) were newly developed as single copy type PCR-based markers. They were used together with 1830 markers previously developed in our lab to construct an integrated map with the Joinmap 3.0 program. This integrated map contained 169 SSR, 354 RFLP, 23 STS from BAC-end sequences, 6 STS from RFLP, 152 AFLP, 51 WRKY, and 99 rRAMP markers on 12 chromosomes. The integrated map contained four genetic maps of two interspecific (Capsicum annuum ‘TF68’ and C. chinense ‘Habanero’) and two intraspecific (C. annuum ‘CM334’ and C. annuum ‘Chilsungcho’) populations of peppers. This constructed integrated map consisted of 805 markers (map distance of 1858 cM) in interspecific populations and 745 markers (map distance of 1892 cM) in intraspecific populations. The used pepper STS were first developed from end sequences of BAC clones from Capsicum annuum ‘CM334’. This integrated map will provide useful information for construction of future pepper genetic maps and for assignment of linkage groups to pepper chromosomes.     

Assaying polymorphism at DNA level for genetic diversity diagnostics of the safflower (Carthamus tinctorius L.) world germplasm resources

Carthamus tinctorius (2n = 2x = 24), commonly known as safflower, is widely cultivated in agricultural production systems of Asia, Europe, Australia, and the Americas as a source of high quality vegetable and industrial oil. Twenty-two RAPD primers, 18 SSR primers, and 10 AFLP primer combinations were used to assess: (1) the genetic diversity of 85 accessions (originating from 24 countries) representing global germplasm variability of safflower and (2) the interrelationships among safflower ‘centers of similarity’ or ‘regional gene pools’ proposed earlier. The RAPD and SSR primers and AFLP primer combinations revealed 57.6, 68.0, and 71.2% polymorphism, respectively, among 111, 72, and 330 genetic loci amplified from the accessions. The sum of effective number of alleles (66.44), resolving power (59.16), and marker index (51.3) explicitly revealed the relative superiority of AFLP as a marker system in uncovering variation in safflower. Overall, AFLP markers could recognize ‘centers of similarity’ or ‘regional gene pools’. Analysis of molecular variance and Shannon’s information index provided corroborating evidences for the present and previous studies that concluded fragmentation of safflower gene pool into many gene pools. Divergent directional selection is likely to have played an important role in shaping the diversity. From the practical applications standpoint, the diversity of Iran–Afghanistan gene pool is very high, equivalent to the total diversity of the species. The Far East gene pool is the least diverse. The present comprehensive input, first of its own kind in safflower, will assist marker based improvement programmes in the crop.     

A genetic linkage map for an apricot (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) BC<Subscript>1</Subscript> population mapping <Emphasis Type="Italic">plum pox virus</Emphasis> resistance

Plum pox virus (sharka; PPV) can cause severe crop loss in economically important Prunus species such as peach, plum, apricot, and cherry. Of these species, certain apricot cultivars (‘Stark Early Orange’, ‘Goldrich’, ‘Harlayne’) display significant levels of resistance to the disease and are the genetic substrate for studies of several xlaboratories working cooperatively to genetically characterize and mark the resistance locus or loci for marker-assisted breeding. The goals of the work presented in this communication are the characterization of the genetics of PPV resistance in ‘Stark Early Orange’ and the development of co-dominant molecular markers for marker-assisted selection (MAS) in PPV resistance breeding. We present the first genetic linkage map for an apricot backcross population of ‘Stark Early Orange’ and the susceptible cultivar ‘Vestar’ that segregates for resistance to PPV. This map is comprised of 357 loci (330 amplified fragment length polymorphisms (AFLPs), 26 simple sequence repeats (SSRs), and 1 morphological marker for PPV resistance) assigned to eight linkage groups. Twenty-two of the mapped SSRs are shared in common with genetic reference map for Prunus (T × E; Joobeur et al. 1998) and anchor our apricot map to the general Prunus map. A PPV resistance locus was mapped in linkage group 1 and four AFLP markers segregating with the PPV resistance trait, identified through bulk segregant analysis, facilitated the development of SSRs in this region. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Lalli, D.A. and Salava, J. contributed equally to this work.     

A framework map from grapevine V3125 (Vitis vinifera ‘Schiava grossa’?×?‘Riesling’)?×?rootstock cultivar ‘B?rner’ (Vitis riparia?×?Vitis cinerea) to localize genetic determinants of phylloxera root resistance

Grapevine rootstock cultivar ‘B?rner’ is a hybrid of Vitis riparia and Vitis cinerea Arnold that shows high resistance to phylloxera (Daktulosphaira vitifoliae Fitch). To localize the determinants of phylloxera root resistance, the susceptible grapevine V3125 (Vitis vinifera ‘Schiava grossa’ × ‘Riesling’) was crossed to ‘B?rner’. Genetic framework maps were built from the progeny. 235 microsatellite markers were placed on the integrated parental map. They cover 1,155.98 cM on 19 linkage groups with an average marker distance of 4.8 cM. Phylloxera resistance was scored by counting nodosities after inoculation of the root system. Progeny plants were triplicated and experimentally infected in 2 years. A scan of the genetic maps indicated a quantitative trait locus on linkage group 13. This region was targeted by six microsatellite-type markers newly developed from the V. vinifera model genome sequence. Two of these appear closely linked to the trait, and can be useful for marker-assisted breeding.     

Genetic analyses of the host-pathogen system Turnip yellows virus (TuYV)—rapeseed (Brassica napus L.) and development of molecular markers for TuYV-resistance

The aphid transmitted Turnip yellows virus (TuYV) has become a serious pathogen in many rapeseed (Brassica napus L.) growing areas. Three-years’ field trials were carried out to get detailed information on the genetics of TuYV resistance derived from the resynthesised B. napus line ‘R54’ and to develop closely linked markers. F₁ plants and segregating doubled-haploid (DH) populations derived from crosses to susceptible cultivars were analysed using artificial inoculation with virus-bearing aphids, followed by DAS-ELISA. Assuming a threshold of E ₄₀₅ = 0.1 in ELISA carried out in December, the results led to the conclusion that pre-winter inhibition of TuYV is inherited in a monogenic dominant manner. However, the virus titre in most resistant lines increased during the growing period, indicating that the resistance is incomplete and that the level of the virus titre is influenced by environmental factors. Bulked-segregant marker analysis for this resistance locus identified two closely linked SSR markers along with six closely linked and three co-segregating AFLP markers. Two AFLP markers were converted into co-dominant STS markers, facilitating efficient marker-based selection for TuYV resistance. Effective markers are particularly valuable with respect to breeding for TuYV resistance, because artificial inoculation procedures using virus-bearing aphids are extremely difficult to integrate into practical rapeseed breeding programs.     

Construction of a dense genetic linkage map for apple rootstocks using SSRs developed from Malus ESTs and Pyrus genomic sequences

Marker-assisted selection (MAS) offers quick and reliable prediction of the phenotypes of seedlings in large populations and thus opens new approaches for selection to breeders of apple (Malus x domestica Borkh.). The development of framework maps enables the discovery of genetic markers linked to desired traits. Although genetic maps have been reported for apple scion cultivars, none has previously been constructed for apple rootstocks. We report the construction of framework genetic maps in a cross between ‘M.9’ (‘Malling 9’) and ‘R.5’ (‘Robusta 5’) apple rootstocks. The maps comprise 224 simple sequence repeat (SSR) markers, 18 sequence-characterised amplified regions, 14 single nucleotide polymorphisms and 42 random amplified polymorphic DNAs. A new set of 47 polymorphic SSRs was developed from apple EST sequences and used for construction of this rootstock map. All 17 linkage groups have been identified and aligned to existing apple genetic maps. The maps span 1,175.7 cM (‘M.9’) and 1,086.7 cM (‘R.5’). To improve the efficiency of mapping markers to this framework map, we developed a bin mapping set. Applications of these new genetic maps include the elucidation of the genetic basis of the dwarfing effect of the apple rootstock ‘M.9’ and the analysis of disease and insect resistance traits such as fire blight (Erwinia amylovora), apple scab (Venturia inaequalis) and woolly apple aphid (Eriosoma lanigerum). Markers for traits mapped in this population will be of direct use to apple breeders for MAS and for identification of causative genes by map-based cloning.     

Origin of resistance to <Emphasis Type="Italic">plum pox virus</Emphasis> in Apricot: what new AFLP and targeted SSR data analyses tell

Amplified fragment length polymorphisms (AFLP) and targeted simple sequence repeats (SSR) were employed to assess genetic similarity of North American apricots having natural resistance to plum pox virus (PPV) within diversified germplasm including six nondomesticated apricot species. On a dendrogram constructed from 231 AFLP loci, the position of the North American cultivars reflects relatedness to the European apricots and introgression of non-European germplasm as well. The occurrence of diagnostic AFLP markers supports an introgression of Chinese germplasm into the North American PPV resistant assortment and supports a different breeding history for ‘Stark Early Orange’ (SEO) and Goldrich-Harlayne lineages. Five SSR loci linked to the PPV resistance region on G1 provided evidence that the investigated lineages (SEO and ‘Harlayne’–‘Goldrich’) have the same or related source of resistance introduced presumably from Northern China. Possible introgression of genetic material from nondomesticated apricots P. mandshurica sp, P. sibirica var. davidiana and P. mume sp. was detected and discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Microsatellite and sequence-tagged site markers diagnostic for the rice bacterial leaf blight resistance gene xa-5

 Microsatellite and sequence-tagged site (STS) markers tightly linked to the bacterial leaf blight (BLB) resistance gene xa-5 were identified in this study. A survey was conducted to find molecular markers that detected polymorphisms between the resistant (IRBB5) and susceptible (‘IR24’) nearly isogenic lines for xa-5, and between Chinsurah Boro II (CBII), an alternative source of xa-5, and a widely planted variety (‘IR64’) that lacks xa-5. Two F₂ populations, from the crosses ‘IR24’×IRBB5 and CBIIבIR64’, were used to estimate linkage based on marker genotype and reaction to disease inoculation with Xanthomonas oryzae pv. oryzae. Two RFLP clones, RZ390 and RG556, were found to co-segregate with xa-5 and were converted into STS markers. A microsatellite marker, RM390, was developed based on a simple sequence repeat in the 5′ untranslated region of the cDNA probe, RZ390, and found to co-segregate with resistance. Two other microsatellites, RM122 and RM13, were located 0.4 cM and 14.1 cM away from xa-5. A germplasm survey of diverse lines containing BLB resistance genes using automated fluorescent detection indicated the range of allelic diversity for each of the microsatellite loci linked to xa-5 and confirmed their usefulness in following genes through the narrow crosses typical of a breeding program. The limited number of alleles observed at the microsatellite loci linked to the resistance gene in 35 xa-5-containing accessions suggested either a single ancestral origin or a few independent origins of the xa-5 gene. PCR-based markers, like the ones developed in this study, are economical and easy to use, and have applicability in efforts to pyramid the recessive xa-5 gene with other BLB resistance genes. Received: 27 September 1996/Accepted: 7 February 1997     

Classification of rice germplasm: III. High-resolution fingerprinting of cytoplasmic genetic male-sterile (CMS) lines with AFLP

 The cytoplasmic genetic male-sterile (CMS) lines developed at the International Rice Research Institute are valuable in producing tropical rice hybrids. Efficient use of CMS lines in hybrid rice production will depend on their level of genetic diversity. Aside from morphological characterization, molecular analysis based on DNA markers can provide information on the genetic diversity of the germplasm. The Amplified Fragment Length Polymorphism (AFLP) technique was used to fingerprint 71 CMS lines and four rice cultivars, ‘IR64’, ‘Azucena’, ‘IR74’, and ‘FR13A’. Eleven primer pair combinations specific to the enzymes PstI and MseI were used to generate 530 AFLP markers, 176 of which were polymorphic. Each CMS line revealed a distinct fingerprint. The AFLP marker-based dendrogram depicted genetic variation among the CMS lines. The CMS lines developed in japonica background grouped with ‘Azucena’, a japonica cultivar. None of the CMS lines clustered with ‘FR13A’, a flood-tolerant traditional indica variety. ‘IR64’ was found to be distinct from the other indica CMS lines and clustered with lines developed in its background. The grouping of CMS lines into a few groups is useful for breeders in selecting genetically diverse CMS lines for hybrid rice production and in avoiding test crossing every CMS line empirically. This study demonstrated that AFLP is a powerful and reliable tool in determining the genetic relationships and in producing distinct fingerprints of rice cultivars. Received: 20 December 1996 / Accepted: 9 October 1997     

Multiple field and glasshouse assessments increase the reliability of linkage mapping of the Vf source of scab resistance in apple

 Apple scab, caused by the fungus Venturia inaequalis (Cke.) Wint., is an important disease in commercial apple production. A mapping population of 155 individuals, derived from a cross between the apple varieties ‘Prima’ (resistant)בFiesta’ (susceptible), was scored for response to the disease in replicated field and glasshouse trials throughout Europe. Twenty data sets were selected and cluster analysis was used to form a consensus score for the population fitting a 1 : 1 segregation ratio of resistance:susceptibility. The progeny were scored with molecular markers. A detailed map covering 54 cM of the ‘Prima’ linkage group containing the Vf gene for scab resistance was constructed using 24 molecular markers linked to the resistance gene. One isoenzyme marker (Pgm-1), six RFLP markers and 17 RAPD markers formed a linkage group with the consensus measure of resistance to scab. Four marker bridges were established with the corresponding ‘Fiesta’ linkage group with additional markers (one isozyme, one RFLP, three RAPD and one AFLP). A low chi-square value indicated a good fit of the marker ordering, which was in close agreement with previously reported linkage positions for some of the markers and Vf. Differences were observed in the ability of different scoring methods to resolve susceptible and resistant classes. The results obtained for the consensus classification of resistance to scab for the population may suggest the presence of virulent inocula at some sites, which could overcome the Vf gene for resistance. The consequences of relying on individual scoring occasions for studying Vf scab resistance are discussed in the context of linkage analysis, conventional breeding selection, and marker-assisted selection. Received: 23 July 1997 / Accepted: 31 October 1997     

Diversity of selected hop cultivars detected by fluorescent AFLPs

 The amplified fragment length polymorphism (AFLP) technique was used to assay eight hop cultivars. The application of fluorescent-labelled primers proved to be a valuable tool and substituted radiolabelling. Digestion with the enzymes EcoRI/ MseI and amplification with primers having three selective bases at the 3’end resulted in distinct banding patterns for imaging with a fluorescent scanner. A total of 523 AFLP fragments derived from eight primer combinations were analysed. On average, 18 polymorphisms per combination were displayed. The Saazer “noble” hop cultivars ‘Saazer’, ‘Tettnanger’ and ‘Spalter’ could not be discriminated. The lowest genetic similarity (GS) between lines was computed for the bitter hops ‘Hallertauer Magnum’ and ‘Wye Target’: GS value of 0.89. The high level of genetic similarity of the analysed hop cultivars is discussed. Received: 11 August 1997 / Accepted: 22 August 1997     

High-resolution genetic mapping of the pepper (Capsicum annuum L.) resistance loci Me3 and Me4 conferring heat-stable resistance to root-knot nematodes (Meloidogyne spp.)

The PM687 line of Capsicum annuum L. has a single dominant gene, Me ₃ , that confers heat-stable resistance to root-knot nematodes (RKN). Me ₃ was mapped using doubled-haploid (DH) lines and F₂ progeny from a cross between the susceptible cultivar ’Yolo Wonder’ (’YW’) and the highly resistant line ’PM687’. Bulked-segregant analysis with DNA pools, from susceptible or resistant DH lines, was performed to identify RAPD and AFLP markers linked to Me ₃ . There was no polymorphism between bulks of ten DH lines using over 800 RADP primers (4,000 amplified fragments analysed). Using 512 AFLP primers (74,000 amplified fragments analysed), and bulked DNA templates from 20 resistant and 20 susceptible plants, we identified eight repulsion-phase and four coupling-phase markers linked to Me _3. Analysed in 103 DH progeny, they defined a 56.1-cM interval containing the target gene. The nearest were located 0.5, 1.0, 1.5 and 3.0 centimorgans (cM) on both sides of the gene. Analysis of the F₂ progeny (162 plants) with the nearest coupling-phase marker confirmed its close position. Another resistance gene to RKN, present in ’PM687’ (Me ₄ ), was shown to be linked to Me ₃ , 10 cM from it. In order to localize Me ₃ and Me ₄ on our reference intraspecific pepper linkage map, two AFLP markers were mapped. The Me ₃ nearest marker was 10.1cM from a RAPD marker named Q04_0.3 and 2.7cM from a RFLP marker named CT135. We investigated map-position orthologies between Me ₃ and two other nematode resistance genes, the tomato Mi-3 and the potato Gpa ₂ genes, which mapped in the telomeric region of the short arm of the tomato and potato chromosome 12 (or XII for potato). Received: 23 March 2000 / Accepted: 2 January 2001     

Use of the multi-allelic self-incompatibility gene in apple to assess homozygocity in shoots obtained through haploid induction

 To obtain homozygous genotypes of apple, we have induced haploid development of either the female or the male gametes by parthenogenesis in situ and anther culture, respectively. Of the shoots obtained, which were mainly of a non-haploid nature, some could be derived from fertilised egg cells or from sporophytic anther tissue. In order to select the shoots having a true haploid origin, and thus homozygotes, we decided to use the single multi-allelic self-incompatibility gene as a molecular marker to discriminate homozygous from heterozygous individuals. The rationale behind this approach was that diploid apple cultivars contain 2 different alleles of the S-gene and therefore the haploid induced shoots obtained from them should have only one of the alleles of the single parent. The parental cultivars used were ‘Idared’ (parthenogenesis in situ) and ‘Braeburn’ (androgenesis), and their S-genotypes were known, except for 1 of the ‘Braeburn’S-alleles. To stimulate parthenogenetic development ‘Idared’ styles were pollinated with irradiated ‘Baskatong’ pollen, the S-alleles of the latter (2n) cultivar were also unknown. The cloning and sequence analysis of these 3 unidentified S-alleles, 1 from ‘Braeburn’ and 2 from ‘Baskatong’ is described, and we show that they correspond to the S ₂₄ -, S ₂₆ - and S ₂₇ -alleles. We have optimised a method for analysis of the S-alleles of ‘Idared/Baskatong’- or ‘Braeburn’-derived in vitro plant tissues and have shown that this approach can be applied for the screening of the in vitro shoots for their haploid origin. Received: 18 August 1997 / Accepted: 10 September 1997     

High-resolution mapping of the barley leaf rust resistance gene Rph5 using barley expressed sequence tags (ESTs) and synteny with rice

The rapidly growing expressed sequence tag (EST) resources of species representing the Poacea family and availability of comprehensive sequence information for the rice (Oryza sativa) genome create an excellent opportunity for comparative genome analysis. Extensive synteny between rice chromosome 1 and barley (Hordeum vulgare L.) chromosome 3 has proven extremely useful for saturation mapping of chromosomal regions containing target genes of large-genome barley with conserved orthologous genes from the syntenic regions of the rice genome. Rph5 is a gene conferring resistance to the barley leaf rust pathogen Puccinia hordei. It was mapped to chromosome 3HS, which is syntenic with rice chromosome 1S. The objective of this study was to increase marker density within the sub-centimorgan region around Rph5, using sequence-tagged site (STS) markers that were developed based on barley ESTs syntenic to the phage (P1)-derived artificial chromosome (PAC) clones comprising the distal region of rice chromosome 1S. Five rice PAC clones were used as queries in a blastn search to screen 375,187 barley ESTs. Ninety-four non-redundant EST sequences were identified from the EST database and used as templates to design 174 pairs of primer combinations. As a result, 9 barley EST-based STS markers were incorporated into the ‘Bowman’ × ‘Magnif 102’ high-resolution map of the Rph5 region. More importantly, six markers, including five EST-derived STS sequences, were found to co-segregate with Rph5. The results of this study demonstrate the usefulness of rice genomic resources for efficient deployment of barley ESTs for marker saturation of targeted barley genomic regions.     

A cherry map from the inter-specific cross Prunus avium ‘Napoleon’ × P. nipponica based on microsatellite, gene-specific and isoenzyme markers

One hundred and sixty microsatellite (simple sequence repeat (SSR)) and six gene-specific markers revealing 174 loci were scored in 94 seedlings from the inter-specific cross of Prunus avium ‘Napoleon’ × Prunus nipponica accession F1292. The co-segregation data from these markers were used to construct a linkage map for cherry which spanned 680 cM over eight linkage groups with an average marker spacing of 3.9 cM per marker and just six gaps longer than 15 cM. Markers previously mapped in Prunus dulcis ‘Texas’ × Prunus persica ‘Earlygold’ allowed the cherry map to be anchored to the peach × almond map and showed the high level of synteny between the species. Eighty-four loci segregated in P. avium ‘Napoleon’ versus 159 in P. nipponica. The segregations of 32 isoenzyme loci in a subset of 47 seedlings from the progeny were scored, using polyacrylamide gel electrophoresis and/or isoelectric focusing separation followed by activity staining, and the co-segregation data were analysed along with those for 39 isoenzymes reported previously and for the 174 sequence-tagged site loci plus an additional two SSR loci. The second map incorporates 233 loci and spans 736 cM over eight linkage groups with an average marker spacing of 3.2 cM per marker and just two gaps greater than 15 cM. The microsatellite map will provide a useful tool for cherry breeding and marker-assisted selection and for synteny studies within Prunus; the gene-specific markers and isoenzymes will be useful for comparisons with maps of other rosaceous fruit crops. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular mapping of leaf rust resistance gene <Emphasis Type="Italic">Rph14</Emphasis> in <Emphasis Type="Italic">Hordeum vulgare</Emphasis>

An incompletely dominant gene conferring resistance to Puccinia hordei, Rph14, identified previously in an accession of Hordeum vulgare, confers resistance to all known pathotypes of P. hordei in Australia. Knowledge of the chromosomal location of Rph14 and the identification of DNA markers closely linked to it will facilitate combining it with other important leaf rust resistance genes to achieve long lasting resistance. The inheritance of Rph14 was confirmed using 146 and 106 F₃ lines derived from the crosses ‘Baudin’/‘PI 584760’ (Rph14) and ‘Ricardo’/‘PI 584760’ (Rph14), respectively. Bulk segregant analysis on DNA from the parental genotypes and resistant and susceptible DNA bulks using DArT markers located Rph14 to the short arm of chromosome 2H. DArT marker bPb-1664 was identified as having the closest genetic association with Rph14. PCR based marker analysis identified a single SSR marker, Bmag692, linked closely to Rph14 at a map distance of 2.1 and 3.8 cm in the ‘Baudin’/‘PI 584760’and ‘Ricardo’/‘PI 584760’ populations, respectively.