Mapping quantitative trait loci for kernel composition in almond

Background Almond breeding is increasingly taking into account kernel quality as a breeding objective. Information on the parameters to be considered in evaluating almond quality, such as protein and oil content, as well as oleic acid and tocopherol concentration, has been recently compiled. The genetic control of these traits has not yet been studied in almond, although this information would improve the efficiency of almond breeding programs. Results A map with 56 simple sequence repeat or microsatellite (SSR) markers was constructed for an almond population showing a wide range of variability for the chemical components of the almond kernel. A total of 12 putative quantitative trait loci (QTL) controlling these chemical traits have been detected in this analysis, corresponding to seven genomic regions of the eight almond linkage groups (LG). Some QTL were clustered in the same region or shared the same molecular markers, according to the correlations already found between the chemical traits. The logarithm of the odds (LOD) values for any given trait ranged from 2.12 to 4.87, explaining from 11.0 to 33.1 % of the phenotypic variance of the trait. Conclusions The results produced in the study offer the opportunity to include the new genetic information in almond breeding programs. Increases in the positive traits of kernel quality may be looked for simultaneously whenever they are genetically independent, even if they are negatively correlated. We have provided the first genetic framework for the chemical components of the almond kernel, with twelve QTL in agreement with the large number of genes controlling their metabolism

Genetic Diversity in Local Spanish Olive Cultivars Assessed by Molecular Characterization with : abstract

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Identificación de regiones genómicas de almendro en progenies de híbridos interespecíficos (abstract)

La mejora genética de portainjertos tiene por objetivo obtener diferentes híbridos interespecíficos y combinar la tolerancia a estreses abióticos. Distintos cruzamientos entre almendro, melocotonero y ciruelo se están estudiado para su adaptación a un amplio rango de condiciones edafoclimáticas. En este estudio analizamos 49 individuos de cuatro progenies de híbridos interespccíficos de tres especies y sus parentales (dos ciruelos mirobolanes: 'P.2175' y 'P.2980'; los híbridos almendro x melocotonero 'Garnem' y 'Felinem'; el almendro 'Garfi'; y el melocotonero 'Nemared'). Se analizaron 48 SSRs polimórficos en los parentales a lo largo de los 8 grupos de ligamiento a partir de varios mapas de referencia de Prunus. El dendrograma UPGMA generado con la variabilidad genética observada, clasificó los genotipos en 5 grupos, permitiéndonos diferenciar en nuestras progenies las regiones genómicas del almendro entre las regiones del melocotonero y el ciruelo. En estas regiones se va a llevar a cabo el estudio de distintos genes implicados en la tolerancia a la sequía, puesto que el almendro es más tolerante que las otras dos especies, melocotonero y cirueloPublishe

Identification of almond genomic regions in four 3-way interspecific hybrid progenies (abstract)

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Association mapping for kernel phytosterol content in almond

Almond kernels are a rich source of phytosterols, which are important compounds for human nutrition. The genetic control of phytosterol content has not yet been documented in almond. Association mapping (AM), also known as linkage disequilibrium (LD), was applied to an almond germplasm collection in order to provide new insight into the genetic control of total and individual sterol contents in kernels. Population structure analysis grouped the accessions into two principal groups, the Mediterranean and the non-Mediterranean. There was a strong subpopulation structure with LD decaying with increasing genetic distance, resulting in lower levels of LD between more distant markers. A significant impact of population structure on LD in the almond cultivar groups was observed. The mean r2-value for all intra-chromosomal loci pairs was 0.040, whereas, the r2 for the inter-chromosomal loci pairs was 0.036. For analysis of association between the markers and phenotypic traits five models were tested. The mixed linear model (MLM) approach using co-ancestry values from population structure and kinship estimates (K model) as covariates identified a maximum of 13 significant associations. Most of the associations found appeared to map within the interval where many candidate genes involved in the sterol biosynthesis pathway are predicted in the peach genome. These findings provide a valuable foundation for quality gene identification and molecular marker assisted breeding in almond.Publishe

Self-compatibility in Prunus species : diversity of mutations

Self-compatibility (SC) is an interesting horticultural trait. Molecular approaches have been recently applied to the elucidation of the interacting pollen-pistil mechanism and to the identification of the genes involved in pistil-pollen recognition. Both mutations of the pistil S-RNases and the pollen SFBs have been reported to explain the changes in the S allele expression. Stylar-part mutations have revealed that ribonuclease activity of the S-RNases is required to inhibit pollen growth. A defective function of the pollen may also give rise to SC. Breakdown of SI has also been associated with mutations affecting modifier loci unlinked to the S-locus. Additionally, a double phenotypic expression of the same genotype has been observed. The nature of these different mutations has only been identified in a few cases, including deletions, insertions, shift mutations and, more recently, epigenetic changes.EUCARPIA. European Association for Research on Plant Breedin

Pollen Tube Growth and Self-Compatibility in Almond

Although pollen tube growth has been an important criterion for self-compatibility evaluation in almond, there is not a clear-cut separation between positive and negative growth of pollen tubes in the different genotypes. The examination of pollen tube growth after selfing almond seedlings has allowed establishing different levels of compatibility, but not a clear-cut separation between self-compatible (SC) and self-incompatible (SI) genotypes, related to the presence of pseudo-self-compatibility in almond. Consequently, a relationship between pollen tube growth and self-compatibility in almond may be established for evaluating the seedlings in breeding programs.almondPrunus amygdalus Batschpollen tube growthself-compatibilityPublishe

Une activation possible de l’allèle Sf chez l’amandier

Self-compatibility has become the primary objective of most almond (Prunus amygdalus Batsch) breeding programmes in order to avoid the problems related to the gametophytic self-incompatibility (GSI) system present in almond, as in other species of the genus Prunus, belonging to the Rosaceae family. Self-incompatibility is a mechanism in flowering plants which prevents self-fertilization and promotes out-crossing. The S locus encodes for ribonucleases expressed in the style (S-RNase) and for F-box proteins expressed in the pollen (SFB). Interactions between both genes are suspected of being involved in determining the specific self pollen and with same haplotype rejection. As this mechanism is still not fully understood, a progeny of 90 seedlings from the cross 'Vivot' (S23Sf?) 'Blanquerna' (SfSf?) was studied because the microscopic observation of pollen tube growth after self-pollination during several years showed an unexpected self-incompatible behaviour in most seedlings. Although the zymograms from stylar ribonucleases and the PCR products using specific and consensus primers allowed distinguishing the individuals with SI or SC genotype, the expression of the Sf allele was not the same in all cases, as shown by the SI phenotype of many seedlings with a SC genotype, suggesting a possible differential expression of Sf. Cloning and sequencing of the SFBs in the two parents may allow to determine whether they have a different protein expression and also to closely study the pollen-expressed F-box genes in almondL'auto-compatibilité est devenue l'objectif prioritaire de la plupart des programmes d'amélioration génétique de l'amandier (Prunus amygdalus Batsch) pour éviter les problèmes liés à la présence du système d'auto-incompatibilité gamétophytique de l'amandier, comme chez d'autres espèces du genre Prunus, appartenant à la famille Rosaceae. L'auto-incompatibilité est un mécanisme des plantes qui empêche leur auto-fertilisation en favorisant le croisement entre les différents génotypes. Le locus S code pour une ribonucléase exprimée dans le style (S-RNase) et aussi pour une protéine exprimée dans le pollen (SFB). Les interactions entre les deux gènes sont suspectées d’être déterminantes du pollen spécifique ainsi que du pollen avec le même haplotype. Comme ce mécanisme n'est pas encore bien compris, une famille de 90 individus provenant du croisement 'Vivot' (S23Sf?) 'Blanquerna' (SfSf?) a été étudiée parce que l'observation microscopique de la croissance des tubes polliniques après l'autopollinisation pendant plusieurs années a montré un comportement auto-incompatible inattendu chez la plupart des individus. Malgré que les zimogrammes des ribonucléases stylaires et les produits de PCR avec des primers spécifiques et primers consensus ont permis de distinguer les génotypes AI ou AC, l'expression de l'allèle Sf n'est pas toujours la même, comme le montre le phénotype AI chez beaucoup de plantes ayant un génotype AC, suggérant une possible expression différente de Sf. Après clonage et séquençage des SFB des deux parents, il sera possible de déterminer s'il existe des niveaux différents d'expression de protéine et d'étudier les gènes de F-box exprimés chez l'amandie

Challenges for self-compatibility identification in almond

Several approaches have been used to assess self-compatibility in almond, such as fruit set after self-pollination and bagging, pollen tube growth, and the more recent Sf allele identification by molecular markers and gene sequencing. However, none of these methods has given fully reliable results and all show advantages and limitations. An active Sf allele that does not confer self-compatibility, in spite of its full identity with the inactive Sf allele conferring self-compatibility, has been identified recently, showing that the presence of the Sf allele is not the only requirement for self-compatibility expression in almond and that the coding region of the Sf allele may not be involved in that expression. Mis-sequencing of alleles has also created confusion for allele identification. Thus, a better knowledge of the plant as a whole, and not only of its genotype, is fundamental to understand self-compatibility in almond and evaluate new selections in a breeding program.Peer ReviewedPrunus amygdalus BatschSf allelegene sequencingbreedingallele identificationPublishe