Linkage maps of the apple ( Malus × domestica Borkh.) cvs ‘Ralls Janet’ and ‘Delicious’ include newly developed EST markers

Two apple genetic linkage maps were constructed using amplified fragment length polymorphisms (AFLPs), simple sequence repeats (SSRs), random amplified polymorphic DNAs (RAPDs), and expressed sequence tag (EST)-derived markers in combination with a pseudo-testcross mapping strategy in which the cultivars ‘Ralls Janet’ and ‘Delicious’ were used as the respective seed parents. Mitsubakaido (Malus sieboldii) was used as the pollen parent for each of the segregating F₁ populations. Expressed sequence tag data were obtained from the random sequencing of cDNA libraries constructed from in vitro cultured shoots and maturing fruits of cv ‘Fuji’, which is the offspring of a cross between ‘Ralls Janet’ and ‘Delicious’. In addition, a number of published gene sequences were used to develop markers for mapping. The ‘Ralls Janet’ map consisted of 346 markers (178 AFLPs, 95 RAPDs, 54 SSRs, 18 ESTs, and the S locus) in 17 linkage groups, with a total length of 1082 cM, while that of ‘Delicious’ comprised 300 markers (120 AFLPs, 81 RAPDs, 64 SSRs, 32 ESTs, and the S, Rf, and MdACS-1 loci) on 17 linkage groups spanning 1031 cM. These maps are amenable to comparisons with previously published maps of ‘Fiesta’ and ‘Discovery’ (Liebhard et al., Mol Breed 10:217–241, 2002; Liebhard et al., Theor Appl Genet 106:1497–1508, 2003a) because several of the SSRs (one to three markers per linkage group) were used in all of the maps. Distorted marker segregation was observed in three and two regions of the ‘Ralls Janet’ and ‘Delicious’ maps, respectively. These regions were localized in different parts of the genome from those in previously reported apple linkage maps. This marker distortion may be dependent on the combinations of cultivars used for map construction.     

<Emphasis Type="Italic">Rpv10</Emphasis>: a new locus from the Asian <Emphasis Type="Italic">Vitis</Emphasis> gene pool for pyramiding downy mildew resistance loci in grapevine

A population derived from a cross between grapevine breeding strain Gf.Ga-52-42 and cultivar ‘Solaris’ consisting of 265 F1-individuals was genetically mapped using SSR markers and screened for downy mildew resistance. Quantitative trait locus (QTL) analysis revealed two strong QTLs on linkage groups (LGs) 18 and 09. The locus on LG 18 was found to be identical with the previously described locus Rpv3 and is transmitted by Gf.Ga-52-42. ‘Solaris’ transmitted the resistance-related locus on LG 09 explaining up to 50% of the phenotypic variation in the population. This downy mildew resistance locus is named Rpv10 for resistance to Plasmopara viticola. Rpv10 was initially introgressed from Vitis amurensis, a wild species of the Asian Vitis gene pool. The one-LOD supported confidence interval of the QTL spans a section of 2.1 centi Morgan (cM) corresponding to 314 kb in the reference genome PN40024 (12x). Eight resistance gene analogues (RGAs) of the NBS–LRR type and additional resistance-linked genes are located in this region of PN40024. The F1 sub-population which contains the Rpv3 as well as the Rpv10 locus showed a significantly higher degree of resistance, indicating additive effects by pyramiding of resistance loci. Possibilities for using the resistance locus Rpv10 in a grapevine breeding programme are discussed. Furthermore, the marker data revealed ‘Severnyi’ × ‘Muscat Ottonel’ as the true parentage for the male parent of ‘Solaris’.     

Advertising acceptability: is mollusk olfaction important in seedling selection?

Although seedling herbivory is an important selective filter in many plant communities, how and why seedlings are selected is poorly understood. Here, we examined the putative role of herbivore olfaction in dictating seedling selection. Using a Y-tube olfactometer we compared snail (Helix aspersa) preference for pellets derived from 14-day-old macerated seedlings of nine European grassland (‘Test’) species against standard (‘Control’) pellets derived from lettuce. Snail movement towards ‘Test’ pellets was strongly correlated with seedling acceptability (Pearson’s r ² = 0.86, P > 0.01) and where snails exhibited a positive choice for the ‘Test’ species, the choice was made more quickly for highly acceptable species (r ² = 0.86, P > 0.01). In elucidating a link between seedling acceptability and olfactory response to macerated seedlings, our study suggests that even from an early ontogenetic stage plant selection by snails may be governed by olfactory cues. This finding highlights the need for research on the role of plant volatiles in plant–herbivore interactions to consider more fully interactions operating at the seedling stage.     

Phylogenetic position of the monotypic Des Murs’ Wiretail ( Sylviorthorhynchus desmursii , Aves: Furnariidae) based on mitochondrial and nuclear DNA

Parallelisms and paraphyletic assemblages are common among ovenbirds. Molecular markers are therefore the best approach when studying the evolutionary relationships among the members of this unparalleled diversified family. We obtained nucleotide sequence data from mitochondrial (cytochrome b) and nuclear genes (myoglobin and glyceraldehyde-3-phosphodehydrogenase) and used these to deduce the phylogenetic position of a monotypic genus endemic to the austral temperate rainforests of southern South America, the Des Murs’ Wiretail (Sylviorthorhynchus desmursii Des Murs, 1847, Aves: Furnariidae). Phylogenetic analyses based on maximum parsimony, maximum likelihood and Bayesian inference all converged into a congruent topology, with a basal position of Des Murs’ Wiretail within Synallaxinae together with Tit–Spinetails (Leptasthenura). Our data reject the hypothesis of a phylogenetic relationship between Des Murs’ Wiretail and thistletails (Schizoeaca) which exhibit parallelisms in morphology, tail structure and nest architecture. Using a molecular clock based on the myoglobin intron 2 gene, we estimated a divergence time of Des Murs’ Wiretail from Tit-Spinetails of 14–15 Myr, which is associated with the appearance of sclerophyllous forest elements in Chile at the Middle–Upper Miocene. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

A new SNP haplotype associated with blue disease resistance gene in cotton (Gossypium hirsutum L.)

Resistance to cotton blue disease (CBD) was evaluated in 364 F_2.3 families of three populations derived from resistant variety ‘Delta Opal’. The CBD resistance in ‘Delta Opal’ was controlled by one single dominant gene designated Cbd. Two simple sequence repeat (SSR) markers were identified as linked to Cbd by bulked segregant analysis. Cbd resides at the telomere region of chromosome 10. SSR marker DC20027 was 0.75 cM away from Cbd. DC20027 marker fragments amplified from 3 diploid species and 13 cotton varieties whose CBD resistance was known were cloned and sequenced. One single nucleotide polymorphism (SNP) was identified at the 136th position by sequence alignment analysis. Screening SNP markers previously mapped on chromosome 10 identified an additional 3 SNP markers that were associated with Cbd. A strong association between a haplotype based on four SNP markers and Cbd was developed. This demonstrates one of the first examples in cotton where SNP markers were used to effectively tag a trait enabling marker-assisted selection for high levels of CBD resistance in breeding programs.     

High-resolution genetic map of the <Emphasis Type="Italic">Rvi15</Emphasis> (<Emphasis Type="Italic">Vr2</Emphasis>) apple scab resistance locus

The Rvi15 (Vr2) apple scab resistance locus found in the GMAL 2473 accession has been previously mapped to the top of the Linkage Group 2 (LG2) by analyzing 89 progeny plants of a cross between ‘Idared’ and GMAL 2473. A new population of 989 progeny plants, derived from a cross between ‘Golden Delicious’ and GMAL 2473, has been analyzed with the two SSR markers CH02c02a and CH02f06, previously found to be associated with Rvi15 (Vr2), and with two published markers derived from NBS sequences (ARGH17 and ARGH37) estimated to map close to the Rvi15 (Vr2) locus. ARGH17 and ARGH37, were found to be the closest markers to the resistance locus, bracketing it within an interval of 1.5 cM. The SSRs mapped one on each side of Rvi15 (Vr2). CH02f06 mapped at 2.9 cM from ARGH37 while CH02a02a mapped at 1.7 from ARGH17. The position of Rvi15 (Vr2) respect to CH02a02a indicates that Rvi15 (Vr2) and Rvi4 (Vh4), a second apple scab gene mapped on the top of LG2, are two different resistance genes. In order to develop even more tightly linked markers to Rvi15 (Vr2), ARGH17 was used as the starting point for chromosome walking through the Rvi15 (Vr2) homolog region of the cv. ‘Florina’. A single ‘Florina’ BAC clone, 36I17, was sufficient to span the homologous locus in the new population’s recombinant progeny. Sequencing of the 36I17 BAC clone allowed identifying seven putative ORFs, including two showing a TIR-NBS-LRR structure. Ten additional markers could be developed mapping within a 1.8 cM interval around the Rvi15 (Vr2) resistance gene. ARGH17 and GmTNL1 markers, the latter also derived from NBS-LRR resistance gene homolog sequence, are the closest markers to Rvi15 (Vr2) bracketing it within a 0.5 cM interval. The availability of 12 markers within the Rvi15 (Vr2) region, all within a small physical distance (kbp) in ‘Florina’, suggests that cloning of the Rvi15 (Vr2) apple scab resistance gene from GMAL 2473 will be possible.     

Iso-lines and inbred-lines confirmed loci that underlie resistance from cultivar ‘Hartwig’ to three soybean cyst nematode populations

Soybean [Glycine max (L.) Merr.] cultivars varied in their resistance to different populations of the soybean cyst nematode (SCN), Heterodera glycines, called HG Types. The rhg1 locus on linkage group G was necessary for resistance to all HG types. However, the loci for resistance to H. glycines HG Type 1.3- (race 14) and HG Type 1.2.5- (race 2) of the soybean cyst nematode have varied in their reported locations. The aims were to compare the inheritance of resistance to three nematode HG Types in a population segregating for resistance to SCN and to identify the underlying quantitative trait loci (QTL). ‘Hartwig’, a soybean cultivar resistant to most SCN HG Types, was crossed with the susceptible cultivar ‘Flyer’. A total of 92 F5-derived recombinant inbred lines (RILs; or inbred lines) and 144 molecular markers were used for map development. The rhg1 associated QTL found in earlier studies were confirmed and shown to underlie resistance to all three HG Types in RILs (Satt309; HG Type 0, P = 0.0001 R ² = 22%; Satt275; HG Type 1.3, P = 0.001, R ² = 14%) and near isogeneic lines (NILs; or iso-lines; Satt309; HG Type 1.2.5-, P = 0.001 R ² = 24%). A new QTL underlying resistance to HG Type 1.2.5- was detected on LG D2 (Satt574; P = 0.001, R ² = 11%) among 14 RILs resistant to the other HG types. The locus was confirmed in a small NIL population consisting of 60 plants of ten genotypes (P = 0.04). This QTL (cqSCN-005) is located in an interval previously associated with resistance to both SDS leaf scorch from ‘Pyramid’ and ‘Ripley’ (cqSDS-001) and SCN HG Type 1.3- from Hartwig and Pyramid. The QTL detected will allow marker assisted selection for multigenic resistance to complex nematode populations in combination with sudden death syndrome resistance (SDS) and other agronomic traits.     

In vitro assay of native Iranian almond species (<Emphasis Type="Italic">Prunus</Emphasis> L. spp.) for drought tolerance

Eight native Iranian almond species from three sections, ‘Euamygdalus’ (Prunus communis; Prunus eleagnifolia and Prunus orientalis); ‘Lycioides’ (Prunus lycioides and Prunus reuteri) and ‘Spartioides’ (Prunus arabica, Prunus glauca and Prunus scoparia) were in vitro screened for drought tolerance using sorbitol and polyethylene glycol (PEG) as an osmoticum. Different levels of water stress were induced using five concentrations of either sorbitol or polyethylene glycol in Woody Plant Medium (WPM). Water potential of various media ranged from −0.80 to −2.05 MPa and water stress in culture medium adversely affected plantlet growth. Wild species from ‘Spartioides’ were less affected than ‘Lycioides’ and ‘Euamygdalus’. At the same level of water potential, sorbitol had lower adverse effects than PEG; the latter being severe. Prunus × sorbitol and Prunus × PEG interactions were significant. At 0.2 M sorbitol and 0.003 M PEG, ‘Spartioides’ produced significantly more roots with higher total root length and root volume, as well as root-dry weight than those of ‘Lycioides’ and ‘Euamygdalus.’ It is concluded that in vitro screening of native Iranian almond species under specific and limited water-stress conditions may provide a system for effectively differentiating the wild species of almond for their expected root mass production under field conditions.     

Biorefining of precious metals from wastes: an answer to manufacturing of cheap nanocatalysts for fuel cells and power generation via an integrated biorefinery?

Bio-manufacturing of nano-scale palladium was achieved via enzymatically-mediated deposition of Pd from solution using Desulfovibrio desulfuricans, Escherichia coli and Cupriavidus metallidurans. Dried ‘Bio-Pd’ materials were sintered, applied onto carbon papers and tested as anodes in a proton exchange membrane (PEM) fuel cell for power production. At a Pd(0) loading of 25% by mass the fuel cell power using Bio-Pd _{D. desulfuricans} (positive control) and Bio-Pd _{E. coli} (negative control) was ~140 and ~30 mW respectively. Bio-Pd _{C. metallidurans} was intermediate between these with a power output of ~60 mW. An engineered strain of E. coli (IC007) was previously reported to give a Bio-Pd that was >3-fold more active than Bio-Pd of the parent E. coli MC4100 (i.e. a power output of >110 mW). Using this strain, a mixed metallic catalyst was manufactured from an industrial processing waste. This ‘Bio-precious metal’ (‘Bio-PM’) gave ~68% of the power output as commercial Pd(0) and ~50% of that of Bio-Pd _{D. desulfuricans} when used as fuel cell anodic material. The results are discussed in relation to integrated bioprocessing for clean energy.     

The role of topolins in micropropagation and somaclonal variation of banana cultivars ‘Williams’ and ‘Grand Naine’ (<Emphasis Type="Italic">Musa</Emphasis> spp. AAA)

The effect of the cytokinins mT (meta-topolin), mTR (meta-topolin riboside), MemT (meta-methoxy topolin) and MemTR (meta-methoxy topolin riboside) on micropropagation of banana cultivars ‘Williams’ and ‘Grand Naine’ was studied and compared to BA (6-benzylaminopurine). In vitro cultures, at the third sub-culture level, were purchased from African Biotechnologies (Pty) Ltd., South Africa. These were then sub-cultured on MS media containing 7.5, 15 and 30 μM of all the cytokinins tested. Results recorded after 6 weeks of growth demonstrated that there were statistically significant differences between the parameters analyzed for the treatments. Superior multiplication rates were recorded for mT and mTR treatments. This result was consistent when compared to BA at 22.2 μM (previously published standard concentration). Contrary to previous findings with other species, these cytokinins inhibited rooting. The effect on somaclonal variation was not significantly different when BA, mT and mTR were tested at the seventh multiplication cycle for ‘Williams’ banana. These results support the possible use of topolins as an alternative to BA for Cavendish banana tissue culture. The role of these cytokinins on somaclonal variation however, requires a more stringent investigation as the results obtained in this investigation could have been influenced by carry-over effects from the initial cultures.     

Development of two loquat [Eriobotrya japonica (Thunb.) Lindl.] linkage maps based on AFLPs and SSR markers from different Rosaceae species

Loquat [Eriobotrya japonica (Thunb.) Lindl.] is a Rosaceae fruit species of growing interest as an alternative to the main fruit crops. However, only a few genetic studies have been carried out on this species. This paper reports the construction of the first genetic maps of two loquat cultivars based on AFLP and microsatellite markers from Malus, Eriobotrya, Pyrus and Prunus genera. An F₁ population consisting of 81 individuals, derived from the cross between ‘Algerie’ and ‘Zaozhong-6’ cultivars, was used to construct both maps. A total of 111 scorable simple sequence repeat (SSR) loci resulted from the testing of 440 SSR primer pairs in the analyzed progeny and the SSR transferability to Eriobotrya was found to be 74% from apple, 58% from pear and 49% from Prunus spp. In addition, 183 AFLP polymorphic bands were produced using 42 primer combinations. The ‘Algerie’ map was organized in 17 linkage groups covering a distance of 900 cM and comprising 177 loci (83 SSRs and 94 AFLPs) with an average marker distance of 5.1 cM. Self-incompatibility trait was mapped at the distal part of the LG17 linkage group, as previously reported in Malus and Pyrus. The ‘Zaozhong-6’ map covered 870 cM comprising 146 loci (64 SSRs and 82 AFLPs) with an average marker distance of 5.9 cM. The 44 SSRs and the 48 AFLPs share in common by both maps were essentially collinear and, moreover, the order of the 75% of apple and pear SSRs mapped in Eriobotrya was shown to be consistent across the Maloideae subfamily. As a whole, these maps represent a useful tool to facilitate loquat breeding and an interesting framework for map comparison in the Rosaceae.     

Mating Behavior in the Alpine Tiger Moth, <Emphasis Type="Italic">Metacrias huttoni</Emphasis>

The alpine Tiger moth, Metacrias huttoni, of South Island, New Zealand, has adapted to female microptery through unusual courting behavior and behavioral plasticity with regard to copulation position. Courting revolves around male manipulation (‘fluffing’) of the female’s highly derived covering of flocculent setae. This was found to be not only necessary to cue female receptivity, but was also shown to stimulate oviposition. Both freshly pupated (24 h after eclosion) and mature (1 wk after eclosion) virgin females showed significantly greater oviposition after artificial grooming. The standard back-to-back copulatory position of winged moths was replaced in 86% of matings with alternative positions. The structure and functional significance of female setae is examined. A preliminary hypothesis for the origin of the moths’ mating behavior is outlined.     

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.     

A major resistance gene from Russian apple ‘Antonovka’ conferring field immunity against apple scab is closely linked to the <Emphasis Type="Italic">Vf</Emphasis> locus

A major scab resistance gene called Va1 was identified in the Russian apple cultivar ‘Antonovka’ (accession APF22) conferring scab resistance under conditions of natural scab infection in the field. After scab scorings over a period of 3 years, a 1:1 segregation was observed in the mapping population 04/214 (‘Golden Delicious’ × ‘Antonovka’). The Va1 resistance gene provides sufficient broad spectrum resistance that is of use in apple resistance breeding and has been assigned Rvi17 according the proposal for a new scab nomenclature (Bus et al., Acta Horticulturae 814:739–746, 2009). Analysis of simple sequence repeats (SSRs) located on the apple linkage group (LG) 1 showed that the Va1 locus is closely linked (1 cM) to SSR CH-Vf1 known to cosegregate with the Vf locus. A tight genetic association was also observed between a specific cleaved amplified polymorphic sequence marker (ARD-CAPS) developed from the HcrVf paralog Vf2ARD present in ‘Antonovka’, but there is no indication yet for a causal relationship with Vf2ARD. Although the whole race spectrum of Va1 is still unknown, it was obvious that it acts against the scab races 6 and 7 which are able to overcome the resistance of Malus floribunda 821. A second resistance factor (named Va2) was studied by race 1-specific scab tests based on grafted 04/214 clones. A 1:1-segregation ratio was observed, too, but 18 “phenotypic recombinants” were found after comparisons with the field scab data of the same genotypes. Va2 was mapped on LG 1 with a genetic distance of about 15 cM above CH-Vf1. The positions of the newly identified ‘Antonovka’ scab resistance factors are compared with previously reported Va mapping approaches and published results from quantitative trait loci analyses performed with different ‘Antonovka’ genotypes.     

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.     

Assessment of fire blight tolerance in apple based on plant inoculations with Erwinia amylovora and DNA markers

Fire blight (Erwinia amylovora) causes serious damage to pome fruit orchards, and identification of germplasm with heritable disease resistance is therefore crucial. Two dominant SCAR (sequence characterised amplified region) marker alleles (AE10-375 and GE-8019), flanking a previously identified QTL (quantitative trait locus) for resistance to fire blight on ‘Fiesta’ linkage group 7 in apple cultivars related to ‘Cox’s Orange Pippin’, were screened on 205 apple cultivars. Both marker alleles were present in 22% of the cultivars, indicating presence of the QTL allele for tolerance, and both were lacking in 25%, indicating homozygosity for absence of the QTL tolerance allele. However, 33% had only the marker allele AE10-375, while 20% had only GE-8019, suggesting that some cultivars with the dominant alleles for both of the flanking markers can carry these on separate chromosomes and may lack the QTL allele for tolerance. In 2009 and 2010, terminal shoots of greenhouse-grown grafted trees of 21 cultivars (only 20 in 2010) were inoculated with Erwinia amylovora. ‘Idared’ (susceptible) and ‘Enterprise’ (tolerant) were included as controls. Disease severity for each cultivar was expressed as percentage of necrosis in relation to entire length of shoot, and the ranking of cultivars in 2009 and 2010 was compared with a Spearman rank correlation test, P < 0.01. A relationship between presence of both flanking marker alleles for tolerance and level of fire blight tolerance was confirmed with a Mann–Whitney U-test, P < 0.01 in 2009, and P < 0.05 in 2010. A PCO (principal coordinate) analysis based on band profiles obtained with 12 SSR (simple sequence repeat) loci produced three loose clusters, two of which contained known offspring of ‘Cox’s Orange Pippin’, and one with cultivars that were either unrelated or had an unknown origin. Cases where DNA markers did not predict level of fire blight damage as expected, were, however, as common among descendants of ‘Cox’s Orange Pippin’ as among apparently unrelated cultivars. Obviously the ‘Fiesta’ LG 7 QTL has some predictive value, both for known ‘Cox’ relatives and others, but more efficient markers would be desirable for marker-assisted selection.     

Genetic relatedness among some wild cherry (<Emphasis Type="Italic">Prunus</Emphasis> subgenus <Emphasis Type="Italic">Cerasus</Emphasis>) genotypes native to Iran assayed by morphological traits and random amplified polymorphic DNA analysis

Subgenus Cerasus species are useful genetic resources for cherry breeding programs. A total of 17 morphological traits together with 19 random amplified polymorphic DNA (RAPD) primers were used to study 39 accessions including 34 wild Cerasus subgenus genotypes belonging to Prunus avium L., P. cerasus L., P. mahaleb L., P. microcarpa Boiss., P. incana Pall., and P. brachypetala Boiss. species, along with an unknown wild Cerasus sample, two advanced cherry cultivars (‘Lambert’ and ‘Bulgar’), and two rootstocks (‘Colt’ and ‘Gisela 6’). Genotypes were separated into different groups according to their species and collection sites using cluster analysis performed by Ward’s clustering method based on morphological data. Nineteen RAPD primers from 60 screened produced 304 polymorphic reproducible bands (98.15% polymorphism). According to the similarity matrix, the lowest similarity was obtained between P. avium and P. microcarpa samples. A dendrogram was prepared by the unweighted pair-group method with arithmetic average (UPGMA), and the accessions were separated according to their species and geographic origin. In both morphological and molecular results, the advanced cultivars and rootstocks were separated from wild genotypes, and the unknown genotype was grouped with P. mahaleb accessions. Grouping by morphological characteristics was compared with the results of RAPD analysis, with no significant correlations between morphological and molecular data being found. This is the first report of molecular (RAPD) genetic diversity study in wild Cerasus subgenus genotypes from Iran, and the results demonstrate the high potential of RAPD analysis for discrimination of Cerasus subgenus genotypes.     

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.     

A consensus linkage map identifies genomic regions controlling fruit maturity and beta-carotene-associated flesh color in melon (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.)

The nutritional value and yield potential of US Western Shipping melon (USWS; Cucumis melo L.) could be improved through the introgression of genes for early fruit maturity (FM) and the enhancement of the quantity of β-carotene (QβC) in fruit mesocarp (i.e., flesh color). Therefore, a set of 116 F₃ families derived from the monoecious, early FM Chinese line ‘Q 3-2-2’ (no β-carotene, white mesocarp) and the andromonoecious, late FM USWS line ‘Top Mark’ (possessing β-carotene, orange mesocarp) were examined during 2 years in Wisconsin, USA to identify quantitative trait loci (QTL) associated with FM and QβC. A 171-point F_2–3 based map was constructed and used for QTL analysis. Three QTL associated with QβC were detected, which explained a significant portion of the observed phenotypic variation (flesh color; R ² = 4.0–50.0%). The map position of one QTL (β-carM.E.9.1) was uniformly aligned with one carotenoid-related gene (Orange gene), suggesting its likely role in QβC in this melon population and putative relationship with the melon white flesh (wf) gene. Two major (FM.6.1 and FM.11.1; R ² ≥ 20%) and one minor QTL (FM.2.1; R ² = 8%) were found to be associated with FM. This map was then merged with a previous recombinant inbred line (RIL)-based map used to identify seven QTL associated with QβC in melon fruit. This consensus map [300 molecular markers (187 co-dominant melon and 14 interspecific; 10 LG)] provides a framework for the further dissection and cloning of published QTL, which will consequently lead to more effective trait introgression in melon.