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Softening is a hallmark of ripening in fleshy fruits, and has both desirable and undesirable implications for texture and postharvest stability. Accordingly, the timing and extent of pre-harvest ripening and associated textural changes following harvest are key targets for improving fruit quality through breeding. Previously, we identified a large effect locus associated with harvest date and firmness in apple (Malus domestica) using genome-wide association studies (GWAS). Here, we present additional evidence that polymorphisms in or around a transcription factor gene, NAC18.1 , may cause variation in these traits. First, we confirmed our previous findings with new phenotype and genotype data from ∼800 apple accessions. In this population, we compared a genetic marker within NAC18.1 to markers targeting three other firmness-related genes currently used by breeders (ACS1 , ACO1 , and PG1), and found that the NAC18.1 marker was the strongest predictor of both firmness at harvest and firmness after 3 months of cold storage. By sequencing NAC18.1 across 18 accessions, we revealed two predominant haplotypes containing the single nucleotide polymorphism (SNP) previously identified using GWAS, as well as dozens of additional SNPs and indels in both the coding and promoter sequences. NAC18.1 encodes a protein that is orthogolous to the NON-RIPENING (NOR) transcription factor, a regulator of ripening in tomato (Solanum lycopersicum). We introduced both NAC18.1 transgene haplotypes into the tomato nor mutant and showed that both haplotypes complement the nor ripening deficiency. Taken together, these results indicate that polymorphisms in NAC18.1 may underlie substantial variation in apple firmness through modulation of a conserved ripening program. [ABSTRACT FROM AUTHOR]

Key message: A QTL for resistance to several races of black spot co-located with the known Rrd1 locus in Rosa. A polymorphism in muRdr1A linked to black spot resistance was identified and molecular markers were designed. Black spot, caused by Diplocarpon rosae, is one of the most serious foliar diseases of landscape roses that reduces the marketability and weakens the plants against winter survival. Genetic resistance to black spot (BS) exists and race-specific resistance is a good target to implement marker-assisted selection. High-density single nucleotide polymorphism-based genetic maps were created for the female parent of a tetraploid cross between 'CA60' and 'Singing in the Rain' using genotyping-by-sequencing following a two-way pseudo-testcross strategy. The female linkage map was generated based on 227 individuals and included 31 linkage groups, 1055 markers, with a length of 1980 cM. Race-specific resistance to four D. rosae races (5, 7, 10, 14) was evaluated using a detached leaf assay. BS resistance was also evaluated under natural infection in the field. Resistance to races 5, 10 and 14 of D. rosae and field resistance co-located on chromosome 1. A unique sequence of 32 bp in exon 4 of the muRdr1A gene was identified in 'CA60' that co-segregates with D. rosae resistance. Two diagnostic markers, a presence/absence marker and an INDEL marker, specific to this sequence were designed and validated in the mapping population and a backcross population derived from 'CA60.' Resistance to D. rosae race 7 mapped to a different location on chromosome 1. [ABSTRACT FROM AUTHOR]

Kernel morphology characteristics of wheat are complex and quantitatively inherited. A doubled haploid (DH) population of the cross RL4452/‘AC Domain’ was used to study the genetic basis of seed shape. Quantitative trait loci (QTL) analyses were conducted on a total of 18 traits: 14 grain shape traits, flour yield (Fyd), and three agronomic traits (Plant height [Plht], 1000 Grain weight [Gwt], Test weight [Twt]), using data from trial locations at Glenlea, Brandon, and Morden in Manitoba, Canada, between 1999 and 2004. Kernel shape was studied through digital image analysis with an Acurum® grain analyzer. Plht, Gwt, Twt, Fyd, and grain shape QTL were correlated with each other and QTL analysis revealed that QTL for these traits often mapped to the same genetic locations. The most significant QTL for the grain shape traits were located on chromosomes 4B and 4D, each accounting for up to 24.4% and 53.3% of the total phenotypic variation, respectively. In addition, the most significant QTL for Plht, Gwt, and Twt were all detected on chromosome 4D at the Rht-D1 locus. Rht-D1b decreased Plht, Gwt, Twt, and kernel width relative to the Rht-D1a allele. A narrow genetic interval on chromosome 4B contained significant QTL for grain shape, Gwt, and Plht. The ‘AC Domain’ allele reduced Plht, Gwt, kernel length and width traits, but had no detectable effect on Twt. The data indicated that this variation was inconsistent with segregation at Rht-B1. Numerous QTL were identified that control these traits in this population. [ABSTRACT FROM AUTHOR]

Breeding apples is a long-term endeavour and it is imperative that new cultivars are selected to have outstanding consumer appeal. This study has taken the approach of merging sensory science with genome wide association analyses in order to map the human perception of apple flavour and texture onto the apple genome. The goal was to identify genomic associations that could be used in breeding apples for improved fruit quality. A collection of 85 apple cultivars was examined over two years through descriptive sensory evaluation by a trained sensory panel. The trained sensory panel scored randomized sliced samples of each apple cultivar for seventeen taste, flavour and texture attributes using controlled sensory evaluation practices. In addition, the apple collection was subjected to genotyping by sequencing for marker discovery. A genome wide association analysis suggested significant genomic associations for several sensory traits including juiciness, crispness, mealiness and fresh green apple flavour. The findings include previously unreported genomic regions that could be used in apple breeding and suggest that similar sensory association mapping methods could be applied in other plants. [ABSTRACT FROM AUTHOR]

Background: Resistance in plants to pathogen attack can be qualitative or quantitative. For the latter, hundreds of quantitative trait loci (QTLs) have been identified, but the mechanisms of resistance are largely unknown. Integrated nontarget metabolomics and proteomics, using high resolution hybrid mass spectrometry, were applied to identify the mechanisms of resistance governed by the fusarium head blight resistance locus, Fhb1, in the near isogenic lines derived from wheat genotype Nyubai. Findings: The metabolomic and proteomic profiles were compared between the near isogenic lines (NIL) with resistant and susceptible alleles of Fhb1 upon F. graminearum or mock-inoculation. The resistance-related metabolites and proteins identified were mapped to metabolic pathways. Metabolites of the shunt phenylpropanoid pathway such as hydroxycinnamic acid amides, phenolic glucosides and flavonoids were induced only in the resistant NIL, or induced at higher abundances in resistant than in susceptible NIL, following pathogen inoculation. The identities of these metabolites were confirmed, with fragmentation patterns, using the high resolution LC-LTQ-Orbitrap. Concurrently, the enzymes of phenylpropanoid biosynthesis such as cinnamyl alcohol dehydrogenase, caffeoyl-CoA O-methyltransferase, caffeic acid Omethyltransferase, flavonoid O-methyltransferase, agmatine coumaroyltransferase and peroxidase were also up-regulated. Increased cell wall thickening due to deposition of hydroxycinnamic acid amides and flavonoids was confirmed by histochemical localization of the metabolites using confocal microscopy. Conclusion: The present study demonstrates that the resistance in Fhb1 derived from the wheat genotype Nyubai is mainly associated with cell wall thickening due to deposition of hydroxycinnamic acid amides, phenolic glucosides and flavonoids, but not with the conversion of deoxynivalenol to less toxic deoxynivalenol 3-O-glucoside. [ABSTRACT FROM AUTHOR]

Genetic impacts under selective breeding of agricultural crops have been frequently investigated with molecular tools, but inadequate attention has been paid to assess genetic changes under long-term genetic improvement of plant traits. Here we analyzed allelic changes with respect to wheat trait improvement in 78 Canadian hard red spring wheat cultivars released from 1845 to 2004 and screened with 370 mapped SSR markers. The improvements in quality, maturity, yield, disease, stem rust, leaf rust, sawfly resistance, and agronomy were considered. A total of 154 (out of 370) loci with significant allelic changes across 21 chromosomes were detected in the 78 wheat cultivars separated into improved versus non-improved groups for eight traits. The number of significant loci for improving a trait ranged from four for quality to 68 for yield and averaged 35. Many more loci with significant allelic reduction for improving a trait were detected than those with significant allelic increase. Selection for early maturity introduced more alleles, but improving the other traits purged more alleles. Significantly lower numbers of unique alleles were found in the cultivars with improved traits. The distributions of unique allele counts also varied greatly across the 21 chromosomes with respect to trait improvement. Significant SSR variation between two cultivar groups was observed for improvement in seven traits, but not in stem rust. The proportional SSR variation residing between two groups ranged from 0.014 to 0.118. The proportional SSR variations within the improved cultivar groups consistently were much lower than those within the non-improved groups. These findings clearly demonstrate the association between allelic changes and wheat trait improvements and are useful for understanding the genetic modification of the wheat genome by long-term wheat breeding. [ABSTRACT FROM AUTHOR]

A male sterile wheat mutant, Triticum aestivum L. ‘Taigu’, was found in a wheat field in China in 1972. The male sterility was controlled by a single dominant gene that was referred to as Ms2. Recently, this gene was found to be linked to a dwarfing gene through crossing Taigu with the short wheat T. aestivum ‘Ai-Bian 1’ carrying the dwarfing gene Rht-D1c. The objective of this study was to develop molecular markers linked to the male sterility Ms2 gene in common wheat. One hundred and twenty-two near-isogenic lines were developed through backcrossing and sib intercrossing and used as the mapping population for the development of molecular markers. Bulked segregant analysis was used to screen 48 pairs of SSR primers, and a marker, MS2-WMC617, was identified closely linked to the male sterile Ms2 gene that mapped at the distal position of chromosome arm 4DS. The use of the molecular marker MS2-WMC617 can facilitate recurrent selection in a wheat breeding program based on marker-assisted selection. Un blé androstérile nommé Triticum aestivum L. ‘Taigu’ a été trouvé dans un champ de blé en Chine en 1972. L’androstérilité était contrôlée par un seul gène dominant qui a été nommé Ms2. Récemment, il a été trouvé que ce gène était lié à un gène de nanisme en effectuant un croisement entre Taigu et le blé nain T. aestivum ‘Ai Bian 1’, lequel porte le gène nanisant Rht-D1c. L’objectif de la présente étude était d’identifier des marqueurs moléculaires liés au gène d’androstérilité Ms2 chez le blé tendre. Cent vingt deux lignées quasi-isogéniques ont été produites par rétrocroisement et croisement entre lignées sœurs. Cette collection de lignées a été employée comme population de cartographie pour identifier des marqueurs moléculaires. Une analyse de ségrégants groupés (« bulked segregant analysis ») a été utilisée pour cribler 48 paires d’amorces SSR et un marqueur, MS2-WMC617, a été trouvé étroitement lié au gène d’androstérilité Ms2, lequel est situé en position distale sur le bras chromosomique 4DS. L’emploi du marqueur MS2-WMC617 pourra faciliter la sélection récurrente au sein d’un programme de sélection faisant appel à la sélection assistée de marqueurs. [ABSTRACT FROM AUTHOR]

Public concerns about crop uniformity introduced by modern plant breeding and genetic vulnerability to biotic and abiotic stresses have been one of the major forces driving long-term efforts in plant germplasm conservation for future food security. However, such concerns have gained little empirical support, as recent molecular diversity analyses of improved crop gene pools did not reveal much reduction from early to recent breeding efforts. We conducted a genome-wide examination of 75 Canadian hard red spring wheat (Triticum aestivum L.) cultivars released from 1845 to 2004 using 370 simple sequence repeat (or SSR) markers that were widely distributed over all 21 wheat chromosomes. A total of 2280 SSR alleles were detected. Allelic reduction occurred in every part of the wheat genome and a majority of the reduced alleles resided in only a few early cultivars. Significant allelic reduction started in the 1930s. Considering 2010 SSR alleles detected in the 20 earliest cultivars, 38% of them were retained, 18% were new, and 44% were lost in the 20 most recent cultivars. The net reduction of the total SSR variation in 20 recent cultivars was 17%. This clear-cut evidence not only supports the contention that modern plant breeding reduces the genetic diversity of Canadian wheat, but also underlies the need for conserving wheat germplasm and introducing genetic diversity into wheat breeding. [ABSTRACT FROM AUTHOR]

An F1 derived doubled haploid (DH) population of 402 lines from the adapted spring wheat cross Superb (high yielding)/BW278 (low yielding) was developed to identify quantitative trait loci (QTL) associated with yield and yield components. A subset of the population (186 lines) was evaluated in replicated field trials in 2001 and 2002 at six locations in Manitoba and Saskatchewan, Canada. Agronomic parameters, grain yield and yield components including 1,000 grain weight, harvest index, average seed weight spike−1, seed number spike−1 and spikes number m−2 were measured. A genetic map was constructed with 268 microsatellite marker loci and included two morphological genes, reduced plant height, Rht-B1b, and the presence/absence of awns, B1. Composite interval mapping was conducted to estimate the location and effect of QTL associated with the evaluated traits. A total of 53 QTL were identified on 12 chromosomes for the 9 evaluated traits with the coefficient of determination ranging from 0.03 to 0.21 of the total variation. The increase in yield and yield components ranged from 4.5 to 17.1% over the population mean. The five grain yield QTL were detected on chromosomes 1A, 2D, 3B, and 5A and showed a combined increase of 34.4%, over the population mean. The alleles from Superb were associated with increased yield for four of the five QTL. This study identified potential chromosome segments for use in marker-assisted selection to improve yield and yield components in spring wheat. [ABSTRACT FROM AUTHOR]

Leaf rust (caused by Puccinia triticina Eriks.) is an important disease of wheat (Triticum aestivum L.) in North America. This study was conducted to assess the utility of the uncharacterized resistance gene Lr60 (formerly LrW2) for the development of resistant cultivars by demonstrating its novelty, genetic location, and the breadth of resistance that it confers. Haploids of a single gene line carrying Lr60 (RL6172) were pollinated with a susceptible cultivar to generate hybrids with random chromosome deficiencies arising from irregular meiosis of the haploid. Out of 488 hybrids, four were susceptible to leaf rust. All susceptible hybrids lacked several polymorphic microsatellite alleles from RL6172 that are specific to chromosome 1 D. Analysis of an F2 population confirmed that Lr60 was located on the short arm of 1D, 8.4 cM distal to the microsatellite BARC149. Since Lr21 is also located on 1DS a cross was made between single gene lines of Lr21 and Lr60; five susceptible plants recovered in F2 out of 1141 individuals tested were confirmed with progeny tests. This ratio (5:1136) gives an estimated recombination frequency of 13% between Lr21 and Lr60. RL6172 was tested with 37 isolates of P. triticina, encompassing a diversity of virulence found in North America; one isolate was virulent. Lr60 is a novel resistance gene and represents a useful diversification of the genetic resources available in wheat for development of leaf rust resistant cultivars. [ABSTRACT FROM AUTHOR]

Wheat resistance to common bunt is a highly desirable trait for environmentally friendly grain grade protection. Valuable breeding achievements have been made to develop wheat varieties with enhanced resistance to the disease, and mapping of race-specific resistance genes has been reported. However, less is known of the chromosomal regions that control non-race specific resistance to common bunt. In this study, we have characterized a segregating population of 185 doubled haploid spring wheat lines derived from the cross RL4452 × AC Domain. Reactions to a mixture of common bunt races were assessed under field simulated spring-sown conditions in greenhouses in two locations over 2 years. A total 369 polymorphic maker loci including 356 microsatellite loci, five expressed sequences tag (ESTs), and eight genes were used to develop a linkage map. Quantitative trait loci (QTL) analysis using composite interval mapping detected three QTLs associated with common bunt resistance, of which two were located on chromosome 1B and one on chromosome 7A. AC Domain alleles contributed the common bunt resistance at all three QTLs. Usefulness of gene tagging within the identified chromosomal regions for common bunt resistance breeding is discussed. [ABSTRACT FROM AUTHOR]

This study was conducted to identify microsatellite markers (SSR) linked to the adult-plant leaf rust resistance gene Lr22a and examine their cross-applicability for marker-assisted selection in different genetic backgrounds. Lr22a was previously introgressed from Aegilops tauschii Coss. to wheat ( Triticum aestivum L.) and located to chromosome 2DS. Comparing SSR alleles from the donor of Lr22a to two backcross lines and their recurrent parents showed that between two and five SSR markers were co-introgressed with Lr22a and the size range of the Ae. tauschii introgression was 9–20 cM. An F2 population from the cross of 98B34-T4B × 98B26-N1C01 confirmed linkage between the introgressed markers and Lr22a on chromosome 2DS. The closest marker, GWM296, was 2.9 cM from Lr22a. One hundred and eighteen cultivars and breeding lines of different geographical origins were tested with GWM296. In total 14 alleles were amplified, however, only those lines predicted or known to carry Lr22a had the unique Ae. tauschii allele at GWM296 with fragments of 121 and 131 bp. Thus, GWM296 is useful for selecting Lr22a in diverse genetic backgrounds. Genotypes carrying Lr22a showed strong resistance to leaf rust in the field from 2002 to 2006. Lr22a is an ideal candidate to be included in a stack of leaf rust resistance genes because of its strong adult-plant resistance, low frequency of commercial deployment, and the availability of a unique marker. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Statistical methods established for the genetic analysis of quantitative traits can be applied to gene expression data. Quantitative trait locus (QTL) analysis can associate the expression of genes or groups of genes with particular genomic regions, and thereby identify regions regulating gene expression. A segregating population of 41 doubled haploid (DH) lines from the hard red spring wheat cross RL4452 × ‘AC Domain’ was used to map expression level polymorphisms. This population had previously been mapped with microsatellites, and includes a full QTL analysis for agronomic and seed quality traits. Expression analysis on mRNA from developing seed grown in two field locations was conducted on 39 of the 41 DH lines using the Affymetrix GeneChip® Wheat Genome Array. Analysis of the hybridization intensity identified 1484 Affymetrix probe sets in the first location and 10 280 probe sets in the second location, where the hybridization intensity varied significantly between genotypes of the population. A common set of 1455 probe sets differing in intensity between genotypes in both locations was used for mapping, and 542 QTLs were identified that each mapped to a single chromosome interval, illustrating that major gene expression QTLs could be found in wheat. Genomic regions corresponding to multiple gene expression QTLs were identified. Comparison of expression mapping data with physical mapping of wheat expressed sequence tag (EST) sequences using rice synteny, as well as logarithm of odds (LOD) score analysis, showed that both cis- and trans-acting expression QTLs were present. Chromosomes 1D and 4B may contain significant trans-regulatory regions in this population. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lodging resistance is a key objective in pea breeding programs. Implementation of marker-assisted selection (MAS) in early generations could significantly enhance the efficiency of the breeding process compared with conventional selection in the F3 or later generations. The objective of this research was to evaluate the effectiveness of MAS for lodging resistance using a combination of a coupling-phase linked marker A001 and a repulsion-phase linked marker A004 in F2 generation field pea (Pisum salivum L.). Eight F2 populations consisting of 680 plants were scored for the markers. A total of 402 F3 families derived from MAS and 187 F3 families from unselected populations were evaluated for lodging reaction under field conditions. The lowest lodging scores for each population were obtained from plants with the combination of A001 marker presence and A004 marker absence. A higher proportion of lodging resistant F3 families was obtained from this marker combination as compared with phenotypic selection in the F3 generation. MAS was less expensive than phenotypic selection in the field. Thus, A001 and A004 are useful for MAS for lodging resistance in early generation pea breeding populations. [ABSTRACT FROM AUTHOR]

Fusarium head blight of wheat is a major deterrent to wheat production world-wide. The genetics of FHB resistance in wheat are becoming clear and there is a good understanding of the genome location of FHB resistance QTL from different sources such as Sumai3, Wuhan, Nyubai and Frontana. All the components needed for assembling complex genotypes through large-scale molecular breeding experiments are now available. This experiment used high throughput microsatellite genotyping and half-seed analysis to process four independent crosses through a molecular breeding strategy to introduce multiple pest resistance genes into Canadian wheat. This included two backcrosses and selection for a total of six FHB resistance QTL, orange blossom wheat midge resistance ( Sm1) and leaf rust resistance ( Lr21). In addition, the fixation of the elite genetic background was monitored with 45–76 markers to accelerate restoration of the genetic background at each backcross. The strategy resulted in 87% fixation of the elite genetic background on average at the BC2F1 generation and successfully introduced all of the chromosome segments containing FHB, Sm1 and Lr21 resistance genes. The molecular breeding strategy was completed in 25 months, at an equal pace to conventional crossing and selection of spring wheat. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A microsatellite consensus map was constructed by joining four independent genetic maps of bread wheat. Three of the maps were F1-derived, doubled-haploid line populations and the fourth population was ‘Synthetic’ × ‘Opata’, an F6-derived, recombinant-inbred line population. Microsatellite markers from different research groups including the Wheat Microsatellite Consortium, GWM, GDM, CFA, CFD, and BARC were used in the mapping. A sufficient number of common loci between genetic maps, ranging from 52 to 232 loci, were mapped on different populations to facilitate joining the maps. Four genetic maps were developed using MapMaker V3.0 and JoinMap V3.0. The software CMap, a comparative map viewer, was used to align the four maps and identify potential errors based on consensus. JoinMap V3.0 was used to calculate marker order and recombination distances based on the consensus of the four maps. A total of 1,235 microsatellite loci were mapped, covering 2,569 cM, giving an average interval distance of 2.2 cM. This consensus map represents the highest-density public microsatellite map of wheat and is accompanied by an allele database showing the parent allele sizes for every marker mapped. This enables users to predict allele sizes in new breeding populations and develop molecular breeding and genomics strategies. [ABSTRACT FROM AUTHOR]

The large size of the Triticum aestivum genome makes it unlikely that a complete genome sequence for wheat will be available in the near future. Exploiting the conserved genome organization between wheat and rice and existing genomic resources, we have constructed in silico physical mapping software for wheat, assigning a gross physical location(s) into chromosome bins to 22,626 representative wheat gene sequences. To validate the predictions from the software we compared the predicted locations of ten ESTs to their positions experimentally determined by SNP marker analysis. Six of the sequences were correctly positioned on the map including four that demonstrated a high level of colinearity with their orthologous rice genomic region. This tool will facilitate the development of molecular markers for regions of interest and the creation of map-based cloning strategies in areas demonstrating high levels of sequence conservation and organization between wheat and rice. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Single-nucleotide polymorphisms (SNPs) represent a new form of functional marker, particularly when they are derived from expressed sequence tags (ESTs). A bioinformatics strategy was developed to discover SNPs within a large wheat EST database and to demonstrate the utility of SNPs in genetic mapping and genetic diversity applications. A collection of >90 000 wheat ESTs was assembled into contiguous sequences (contigs), and 45 random contigs were then visually inspected to identify primer pairs capable of amplifying specific alleles. We estimate that homoeologue sequence variants occurred 1 in 24 bp and the frequency of SNPs between wheat genotypes was 1 SNP/540 bp (θ = 0.0069). Furthermore, we estimate that one diagnostic SNP test can be developed from every contig with 10-60 EST members. Thus, EST databases are an abundant source of SNP markers. Polymorphism information content for SNPs ranged from 0.04 to 0.50 and ESTs could be mapped into a framework of microsatellite markers using segregating populations. The results showed that SNPs in wheat can be discovered in ESTs, validated, and be applied to conventional genetic studies. [ABSTRACT FROM AUTHOR]

Direct amplification of minisatellite DNA by PCR (DAMD PCR) was used to amplify and subsequently clone several fragments of DNA from crucifer species. The PCR-derived fragments of DNA were generated using known minisatellite core sequences as PCR primers. Southern hybridization of these putative minisatellite DNA fragments revealed that many were genome-specific; they hybridized with high affinity only to the genomic DNA of the species from which they were cloned. The DNA fragments were believed to be dispersed in the genome, based on smear-like hybridization signals on EcoRI-, BamHI-, and HindIII-digested genomic DNA. Genome-specific probes were specifically isolated from Brassica rapa (A genome), Brassica nigra (B genome), and Sinapis alba in addition to several other crucifer species. The sequence of a B. rapa specific probe (pBr17.1.3A) contained a minisatellite region that could be divided into three tandem repeats; each repeat contained between two and five subrepeats and each subrepeat shared a highly conserved core region of 29 bp. This minisatellite sequence also hybridized with high affinity to the A genome species B. napus and B. juncea. This research showed that dispersed, genome-specific probes can be isolated using DAMD PCR and that these probes could be used to detect and quantify alien DNA present in progeny from intergeneric or interspecific crosses.Key words: Brassica, genome specific, marker-assisted selection, minisatellite.L'amplification directe de minisatellites (DAMD PCR) a été utilisée afin d'amplifier et ensuite cloner des fragments d'ADN en provenance de plusieurs espèces de crucifères. Les amplicons ont été produits en utilisant des séquences conservées connues provenant de minisatellites en tant qu'amorces. Des hybridations Southern avec ces minisatellites potentiels a révélé que plusieurs de ceux-ci étaient spécifiques d'un génome du fait qu'ils hybridaient avec grande affinité au seul génome à partir duquel ils avaient été clonés. Il est postulé que ces séquences sont dispersées dans le génome du fait que les signaux d'hybridation présentaient l'aspect d'un dégradé sur l'ADN digéré avec les enzymes EcoRI, BamHI et HindIII. Les sondes spécifiques d'un génome ont été isolées du Brassica rapa (génome A), du B. nigra (génome B) et du Sinapis alba en plus de plusieurs autres crucifères. La séquence de la sonde spécifique du génome du B. rapa (pBr17.1.3A) contenait un minisatellite qui peut être divisé en trois régions répétées en tandem. Chaque unité répétée était composée de deux à cinq sous-motifs répétés et chaque sous-motif possédait une région très conservée de 29 pb. Ce minisatellite hybridait également avec beaucoup d'affinité avec les espèces à génome A : B. napus et B. juncea. Ces travaux montrent que des séquences d'ADN spécifiques d'un génome et dispersées peuvent être isolées par Damd-PCR, une technique qui pourrait être utilisée pour détecter et quantifier de l'ADN étranger présent au sein de la progéniture de croisements intergénériques ou interspécifiques.Mots clés : Brassica, marqueurs spécifique d'un génome, sélection assistée de marqueurs, minisatellite.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The development of yellow-seeded Brassica napus for improving the canola-meal quality characteristics of lower fibre content and higher protein content has been restricted because no yellow-seeded forms of B. napus exist, and their conventional development requires interspecific introgression of yellow seed coat colour genes from related species. A doubled-haploid (DH) population derived from the F[sub 1] generation of the cross 'Apollo' (black-seeded) × YN90-1016 (yellow-seeded) B. napus was analysed via bulked segregant analysis to identify molecular markers associated with the yellow-seed trait in B. napus for future implementation in marker-assisted breeding. A single major gene (pigment 1) flanked by eight RAPD markers was identified co-segregating with the yellow seed coat colour trait in the population. This gene explained over 72% of the phenotypic variation in seed coat colour. Further analysis of the yellow-seeded portion of this DH population revealed two additional genes favouring 'Apollo' alleles, explaining 11 and 8.5%, respectively, of the yellow seed coat colour variation. The data suggested that there is a dominant, epistatic interaction between the pigment 1 locus and the two additional genes. The potential of the markers to be implemented in plant breeding for the yellow-seed trait in B. napus is discussed.Key words: Brassica napus, yellow seed, RAPD.Le développement de Brassica napus à graines jaunes, une caractéristique qui se traduit par un tourteau de canola de meilleure qualité ayant une teneur plus faible en fibres et plus élevée en protéines, est rendu difficile du fait de l'absence de B. napus à graines jaunes. En conséquence le développement par voie conventionnelle d'un tel matériel nécessite le recours à une introgression interspécifique des gènes conférant la couleur jaune aux graines. Une population d'haploïdes doublés (HD), dérivée de la génération F[sub 1] d'un croisement entre 'Apollo' (à graines noires) et YN90-1016 (à graines jaunes), a été analysée par la méthode des ségrégants regroupés (BSA) afin d'identifier des marqueurs moléculaires associés à la couleur jaune des graines chez le B. napus en vue d'éventuellement pratiquer la sélection assistée. Un gène majeur unique (pigment 1), bordé de huit marqueurs RAPD, a montré une co-ségrégation avec la couleur des graines au sein de cette population. Ce gène permet d'expliquer plus de 72 % de la variation phénotypique pour la couleur des graines. Des analyses additionnelles réalisées uniquement sur les lignées HD à graines jaunes ont révélé deux gènes additionnels favorisant les allèles du cv. Apollo, lesquels expliquaient 11 % et 8,5 %, respectivement, de la variation pour la couleur jaune. Ces données suggèrent qu'il existe une interaction épistatique dominante entre le locus pigment 1 et deux gènes additionnels. L'utilité potentielle des marqueurs pour des fins de sélection de la couleur des graines chez le B. napus est discutée.Mots clés : Brassica napus, graines jaunes, RAPD.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Aluminum (Al) stress was examined in three lines of wheat (Triticum aestivum L.) by measuring root lengths, protein synthesis and protein accumulation in seedling root tips grown in a hydroponic system. An Al‐sensitive, recurrent wheat parent (cv. Katepwa) showed very little root growth in low Al concentrations. In contrast, an Al‐tolerant near isogenic line (Alikat) and Al‐tolerant donor (cv. Maringa) had much greater root growth. Segregation data from an F2 population (Katepwa × Alikat) showed that one major gene controlled Al tolerance based on root growth (X2= 0.651). All three lines showed an approximately 2‐fold increase in [35S]‐Met incorporation in root tips after 3 days in Al and a comparable increase in root‐tip dry weight. Maringa and Alikat root tips showed an increased total protein content while Katepwa root tips showed no increase in total protein content during the Al stress. Based on higher specific activities, insoluble proteins were preferentially translated in all three lines during Al stress. Proteinase activity in Katepwa root tips was 1.7‐fold higher during Al stress, with Maringa and Alikat showing no change in proteinase activity. The Al‐induced, increased proteinase activity in Katepwa appeared to inhibit soluble protein accumulation. [ABSTRACT FROM AUTHOR]

The effects of aluminum (Al) exposure on intact root respiration of an Al-sensitive (Scout-66) and an Al-tolerant (Atlas-66) cultivar of Triticum aestivum were investigated. Exposure to a wide range of Al concentrations (0–900 µmol) for 4 days stimulated respiration along the energy-conserving cytochrome pathway in both cultivars and increased the ratio of maintenance respiration to growth respiration. The maximum rate of Scout-66 root respiration occurred after exposure to 100–200 µmol Al. Atlas-66 root respiration peaked after exposure to 300–400 µmol Al. Similarly, calculations of theoretical adenosine 5′-triphosphate (ATP) production indicated that maximum daily rate of ATP production also increased upon exposure to Al in both cultivars, with peak ATP production occurring during peak respiration. Maximum root respiration rates in both cultivars were related to the Al concentration that inhibited root growth. Temporal exposure to 200 µmol Al quickly stopped root growth and stimulated cytochrome pathway respiration in Scout-66 after 4 days. Atlas-66 root growth and respiration were unaffected by 200 µmol Al. These results suggest that Al exposure imposes a demand for additional metabolic energy. A model describing Al effects on root respiration is presented. [ABSTRACT FROM AUTHOR]

A correction to the article "Microsatellite mapping of adult-plant leaf rust resistance gene Lr22a in wheat" that was published in the previous issue is presented.