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Anthocyanin-rich peaches, because of their antioxidant properties and their strong attractiveness to consumers, are increasingly considered in French peach varietal innovation programs that integrate plant genomics and classical breeding. In this study, we describe a new blood-flesh trait identified in the ‘Wu Yue Xian’ peach accession from China. ‘Wu Yue Xian’ exhibits a fully red mesocarp during the later stages of fruit development, both with green midrib leaf and normal growth of the tree. This blood-flesh phenotype clearly differs from that determined by a single recessive locus (bf) in ‘Harrow Blood’, a clone showing blood-flesh in both immature and mature fruit associated with red midrib leaf and reduced tree height. We have then provided genetic evidence that blood-flesh phenotype of ‘Wu Yue Xian’ was controlled by a single dominant locus, designated DBF (Dominant Blood-Flesh), in four successive families derived from this accession. A genetic linkage map of the blood-flesh parent (‘D6090’) of the fourth population was constructed, including 102 SSRs spanning a total distance of 562.3 cM in eight linkage groups. Whereas the bf locus is located to linkage group 4, we mapped DBF to the top of linkage group 5, thus proving that DBF and bf loci are not alleles. Among 64 predicted genes in the DBF region (505 kbp), three genes of the dihydroflavonol-4-reductase family were identified as good candidates for the control of the DBF trait. Furthermore, SSR markers flanking DBF, such as AMPP157 and AMPPG178, supply a good basis to implement marker-assisted selection for this trait.

Recent updates in comparative genomics among cereals have provided the opportunity to identify conserved orthologous set (COS) DNA sequences for cross-genome map-based cloning of candidate genes underpinning quantitative traits. New tools are described that are applicable to any cereal genome of interest, namely, alignment criterion for orthologous couples identification, as well as the Intron Spanning Marker software to automatically select intron-spanning primer pairs. In order to test the software, it was applied to the bread wheat genome, and 695 COS markers were assigned to 1,535 wheat loci (on average one marker/2.6 cM) based on 827 robust rice-wheat orthologs. Furthermore, 31 of the 695 COS markers were selected to fine map a pentosan viscosity quantitative trait loci (QTL) on wheat chromosome 7A. Among the 31 COS markers, 14 (45%) were polymorphic between the parental lines and 12 were mapped within the QTL confidence interval with one marker every 0.6 cM defining candidate genes among the rice orthologous region.

The RMia gene, which confers resistance (R) to the root-knot nematodes (RKN) Meloidogyne incognita and Meloidogyne arenaria, has been shown to segregate in the peach rootstocks Nemared, Shalil, and Juseitou on LG2 of the Prunus map. Here, we report the high-resolution mapping of RMia in Nemared, using the peach genome sequence and 790 individuals from two segregating peach populations, the F2 crossMontclar x Nemared and the four-way cross [(Pamirskij × Rubira) × (Montclar × Nemared)], in which Montclar, Pamirskij, and Rubira are susceptible (S) to RKN. Among the simple sequence repeat (SSR) markers designed for an initial flanking region of more than 1 Mb, five SSR markers specific for Nemared were characterized. The genotyping and phenotyping of recombinant individuals in this interval narrowed the gene’s location to a 300 kb physical distance between the SSR markers AMPP117 and AMPP116. In this interval, SNP polymorphisms were recovered from 1-kb-sequenced DNA fragments that were selected at 20 kb intervals. Two SNP markers (A20SNP and SNP_APP91) were shown to flank the gene in a final 92-kb region, containing four candidate genes from the TIR–NBS– LRR family. Finally, we studied the polymorphism of three closely linked markers, SNP_APP92, SNP_APP91, and AMPP117, on 28 R or S accessions fromdiverse Prunus species or hybrids. These markers discriminated between most R and S accessions, suggesting that at least the R sources of Nemared, Nemaguard, and Shalil share a common resistant ancestor

Knowledge of the genetic control of sugar metabolism is essential to enhance fruit quality and promote fruit consumption. The sugar content and composition of fruits varies with species, cultivar and stage of development, and is controlled by multiple enzymes. A QTL (quantitative trait locus) study was performed on peach fruit [Prunus persica (L.) Batsch], the model species for Prunus. Progeny derived from an interspecific cross between P. persica cultivars and P. davidiana was used. Dynamic QTLs for fresh weight, sugars, acids, and enzyme activities related to sugar metabolism were detected at different stages during fruit development. Changing effects of alleles during fruit growth were observed, including inversions close to maturity. This QTL analysis was supplemented by the identification of genes annotated on the peach genome as enzymes linked to sugar metabolism or sugar transporters. Several cases of co-locations between annotated genes, QTLs for enzyme activities and QTLs controlling metabolite concentrations were observed and discussed. These co-locations raise hypotheses regarding the functional regulation of sugar metabolism and pave the way for further analyses to enable the identification of the underlying genes. In conclusion, we identified the potential impact on fruit breeding of the modification of QTL effect close to maturity.

Peach powdery mildew is one of the major diseases of the peach. Various sources of resistance to PPM have thus been identified, including the single dominant locus Vr2 carried by the peach rootstock 'Pamirskij 5'. To map Vr2, a linkage map based on microsatellite markers was constructed from the F.sub.2 progeny (WP.sup.2) derived from the cross 'Weeping Flower Peach' x 'Pamirskij 5'. Self-pollinations of the parents were also performed. Under greenhouse conditions, all progenies were scored after artificial inoculations in two classes of reactions to PPM (resistant/susceptible). In addition to Vr2, WP.sup.2 segregated for three other traits from 'Weeping Flower Peach': Rm1 for green peach aphid resistance, Di2 for double-flower and pl for weeping-growth habit. With their genomic locations unknown or underdocumented, all were phenotyped as Mendelian characters and mapped: Vr2 mapped at the top of LG8, at 3.3 cM, close to the CPSCT018 marker; Rm1 mapped at the bottom of LG1, at a position of 116.5 cM, cosegregating with the UDAp-467 marker and in the same region as Rm2 from 'Rubira'.sup.®; Di2 mapped at 28.8 cM on LG6, close to the MA027a marker; and pl mapped at 44.1 cM on LG3 between the MA039a and SSRLG3_16m46 markers. Furthermore, this study revealed, for the first time, a pseudo-linkage between two traits of the peach: Vr2 and the Gr locus, which controls the red/green color of foliage. The present work therefore constitutes a significant preliminary step for implementing marker-assisted selection for the four major traits targeted in this study.

Peach powdery mildew is one of the major diseases of the peach. Various sources of resistance to PPM have thus been identified, including the single dominant locus Vr2 carried by the peach rootstock 'Pamirskij 5'. To map Vr2, a linkage map based on microsatellite markers was constructed from the F2 progeny (WP2) derived from the cross 'Weeping Flower Peach' 9 'Pamirskij 5'. Self-pollinations of the parents were also performed. Under greenhouse conditions, all progenies were scored after artificial inoculations in two classes of reactions to PPM (resistant/susceptible). In addition to Vr2, WP2 segregated for three other traits from 'Weeping Flower Peach': Rm1 for green peach aphid resistance, Di2 for double-flower and pl for weeping-growth habit. With their genomic locations unknown or under-documented, all were phenotyped as Mendelian characters and mapped: Vr2 mapped at the top of LG8, at 3.3 cM, close to the CPSCT018 marker; Rm1 mapped at the bottom of LG1, at a position of 116.5 cM, cosegregating with the UDAp-467 marker and in the same region as Rm2 from 'Rubira'(R); Di2 mapped at 28.8 cM on LG6, close to the MA027a marker; and pl mapped at 44.1 cM on LG3 between the MA039a and SSRLG3_16m46 markers. Furthermore, this study revealed, for the first time, a pseudo-linkage between two traits of the peach: Vr2 and the Gr locus, which controls the red/green color of foliage. The present work therefore constitutes a significant preliminary step for implementing marker-assisted selection for the four major traits targeted in this study.

Grain dietary fiber content in wheat not only affects its end use and technological properties including milling, baking and animal feed but is also of great importance for health benefits. In this study, integration of association genetics (seven detected loci on chromosomes 1B, 3A, 3D, 5B, 6B, 7A, 7B) and meta-QTL (three consensus QTL on chromosomes 1B, 3D and 6B) analyses allowed the identification of seven chromosomal regions underlying grain dietary fiber content in bread wheat. Based either on a diversity panel or on bi-parental populations, we clearly demonstrate that this trait is mainly driven by a major locus located on chromosome 1B associated with a log of p value >13 and a LOD score >8, respectively. In parallel, we identified 73 genes differentially expressed during the grain development and between genotypes with contrasting grain fiber contents. Integration of quantitative genetics and transcriptomic data allowed us to propose a short list of candidate genes that are conserved in the rice, sorghum and Brachypodium chromosome regions orthologous to the seven wheat grain fiber content QTL and that can be considered as major candidate genes for future improvement of the grain dietary fiber content in bread wheat breeding programs.

Knowledge of the genetic control of sugar metabolism is essential to enhance fruit quality and promote fruit consumption. The sugar content and composition of fruits varies with species, cultivar and stage of development, and is controlled by multiple enzymes. A QTL (quantitative trait locus) study was performed on peach fruit [Prunus persica (L.) Batsch], the model species for Prunus Progeny derived from an interspecific cross between P. persica cultivars and P. davidiana was used. Dynamic QTLs for fresh weight, sugars, acids, and enzyme activities related to sugar metabolism were detected at different stages during fruit development. Changing effects of alleles during fruit growth were observed, including inversions close to maturity. This QTL analysis was supplemented by the identification of genes annotated on the peach genome as enzymes linked to sugar metabolism or sugar transporters. Several cases of co-locations between annotated genes, QTLs for enzyme activities and QTLs controlling metabolite concentrations were observed and discussed. These co-locations raise hypotheses regarding the functional regulation of sugar metabolism and pave the way for further analyses to enable the identification of the underlying genes. In conclusion, we identified the potential impact on fruit breeding of the modification of QTL effect close to maturity.

The RMia gene, which confers resistance (R) to the root-knot nematodes (RKN) Meloidogyne incognita and Meloidogyne arenaria, has been shown to segregate in the peach rootstocks Nemared, Shalil, and Juseitou on LG2 of the Prunus map. Here, we report the high-resolution mapping of RMia in Nemared, using the peach genome sequence and 790 individuals from two segregating peach populations, the F2 crossMontclar x Nemared and the four-way cross [(Pamirskij × Rubira) × (Montclar × Nemared)], in which Montclar, Pamirskij, and Rubira are susceptible (S) to RKN. Among the simple sequence repeat (SSR) markers designed for an initial flanking region of more than 1 Mb, five SSR markers specific for Nemared were characterized. The genotyping and phenotyping of recombinant individuals in this interval narrowed the gene’s location to a 300 kb physical distance between the SSR markers AMPP117 and AMPP116. In this interval, SNP polymorphisms were recovered from 1-kb-sequenced DNA fragments that were selected at 20 kb intervals. Two SNP markers (A20SNP and SNP_APP91) were shown to flank the gene in a final 92-kb region, containing four candidate genes from the TIR–NBS– LRR family. Finally, we studied the polymorphism of three closely linked markers, SNP_APP92, SNP_APP91, and AMPP117, on 28 R or S accessions fromdiverse Prunus species or hybrids. These markers discriminated between most R and S accessions, suggesting that at least the R sources of Nemared, Nemaguard, and Shalil share a common resistant ancestor