Biochemical Characterization and Differential Expression of PAL Genes Associated With “Translocated” Peach/Plum Graft-Incompatibility

Grafting is an ancient plant propagation technique widely used in horticultural crops, particularly in fruit trees. However, the involvement of two different species in grafting may lead to lack of affinity and severe disorders between the graft components, known as graft-incompatibility. This complex agronomic trait is traditionally classified into two categories: “localized” (weak graft unions with breaks in cambial and vascular continuity at the graft interface and absence of visual symptoms in scion leaves and shoots) and “translocated” (degeneration of the sieve tubes and phloem companion cells at the graft interface causing translocation problems in neighboring tissues, and reddening/yellowing of scion leaves). Over the decades, more attention has been given to the different mechanisms underlying the “localized” type of graft-incompatibility; whereas the phenylpropanoid-derived compounds and the differential gene expression associated with the “translocated” graft-incompatibility remain unstudied. Therefore, the aim of this study was to shed light on the biochemical and molecular mechanisms involved in the typical “translocated” graft-incompatibility of peach/plum graft-combinations. In this study, the “Summergrand” (SG) nectarine cultivar was budded on two plum rootstocks: “Adara” and “Damas GF 1869”. “Translocated” symptoms of incompatibility were shown and biochemically characterized in the case of “SG/Damas GF 1869” graft-combination, 3 years after grafting. Non-structural carbohydrates (soluble sugars and starch), phenolic compounds and antioxidant activity, were significantly enhanced in the incompatible graft-combination scion. Similarly, the enzymatic activities of the antioxidant enzyme peroxidase, the phenylalanine ammonia-lyase (PAL) and polyphenol oxidase involved in the phenylpropanoid pathway were significantly affected by the incompatible rootstock “Damas GF 1869”, inducing higher activities in the scion than those induced by the compatible rootstock “Adara”. In addition, a positive and strong correlation was obtained between total phenol content, antioxidant capacity and the expression of the key genes involved in the phenylpropanoid pathway, PAL1 and PAL2. Regarding the “SG/Adara” graft-combination, there were neither external symptoms of “translocated” incompatibility nor significant differences in the biochemical and molecular parameters between scion and rootstock, proving it to be a compatible combination. The differential expression of PAL genes together with the biochemical factors cited above could be good markers for the “translocated” peach/plum graft-incompatibility.

Genetic analysis for physical nut traits in almond

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Population genetic analysis of brazilian peach breeding germplasm.

ABSTRACT Peach has great economic and social importance in Brazil. Diverse sources of germplasm were used to introduce desirable traits in the Brazilian peach breeding pool, composed mainly by local selections and accessions selected from populations developed by the national breeding programs, adapted to subtropical climate, with low chill requirement, as well as accessions introduced from several countries. In this research, we used SSR markers, selected by their high level of polymorphism, to access genetic diversity and population structure of a set composed by 204 peach selected genotypes, based on contrasting phenotypes for valuable traits in peach breeding. A total of 80 alleles were obtained, giving an average of eight alleles per locus. In general, the average value of observed heterozygosity (0.46) was lower than the expected heterozygosity (0.63). STRUCTURE analysis assigned 162 accessions splitted into two subpopulations based mainly on their flesh type: melting (96) and non-melting (66) flesh cultivars. The remaining accessions (42) could not be assigned under the 80% membership coefficient criteria. Genetic variability was greater in melting subpopulation compared to non-melting. Additionally, 55% of the alleles present in the breeding varieties were also present in the founder varieties, indicating that founding clones are well represented in current peach cultivars and advanced selections developed. Overall, this study gives a first insight of the peach genetic variability available and evidence for population differentiation (structure) in this peach panel to be exploited and provides the basis for genome-wide association studies

Genetic origin and climate determine fruit quality and antioxidant traits on apple (Malus x domestica Borkh)

Apples are highly appreciated in terms of flavor, nutritional and health-promoting compounds and are associated with a reduced risk to develop age-related and chronic diseases. In this study, 155 accessions of Malus x domestica Borkh from the apple germplasm collection, located at the Experimental Station of Aula Dei in NE Spain, were analyzed during five consecutive years (2014–2018). Basic fruit quality traits including soluble solids content (SSC), titratable acidity (TA) and the ratio SSC/TA (ripening index - RI) were obtained. In addition, biochemical compounds such as total phenolics content (TPC), flavonoids (TFC), vitamin C (Ascorbic acid - AsA) and relative antioxidant capacity (RAC) were determined. Statistical analysis was used to determine differences in trait values among accessions and years. The well adapted local accessions showed, in general, higher average content of antioxidants and RAC compared with the foreign and commercial ones. A multivariate model was fitted with the accessions and climate features of each year as independent variables. A cluster analysis was then performed on the model coefficients space to classify the 155 accessions within five groups. The cluster analysis showed that foreign cultivars (those not originating from Spain) were concentrated in two groups while local accessions could not be segregated and had very different profiles. Furthermore, they increased the concentration of bioactive compounds tended to decrease with higher temperatures, while increased with higher solar radiation. Statistical analyses emphasized differences between groups and highlighted accessions and climate as main factors affecting metabolite profiles and fruit characteristics.info:eu-repo/semantics/acceptedVersio

Molecular analyses of evolution and population structure in a worldwide almond [Prunus dulcis (Mill.) D.A. Webb syn. P. amygdalus Batsch] pool assessed by microsatellite markers

A total of 158 almond accessions representative of the diversity of almond across the five continents were included for analysis using 17 microsatellite polymorphic markers. Genetic relationships among genotypes were estimated using cluster analysis, allowing their differentiation in two main groups, one with the domesticated almond cultivars and selections and the other with all wild Prunus species close to almond. The unweighted pair group method average tree drawn from this analysis classified the genotypes according to their geographical origin, confirming the particular evolution of different almond ecotypes. Structure analysis showed a strong subpopulation structure and linkage disequilibrium decaying with increasing genetic linkage distance. Analysis of molecular variance confirmed that most of the genetic variability was within populations. Therefore the connection structure between the different populations and the possible bottlenecks in the expansion of almond cultivars could be established.Angel Fernaández i Martí, Carolina Font i Forcada, Kazem Kamali, María J. Rubio-Cabetas, Michelle Wirthensohn, Rafel Socias i Compan

Genotyping-by-sequencing (GBS) for SNP-based linkage map construction for two Prunus rootstocks from a peach rootstock breeding program

8 Pags.- 2 Figs.- 1 Tabl. The definitive version is available at: https://www.actahort.org/index.htmTrees for commercial production comprise the fruit-bearing scions grafted to a rootstock, thus the choice of an appropriate rootstock is fundamental to orchard success. Even though several SNP-based linkage maps for cultivated Prunus species such as peach, cherries and almond are available, there are no SNP-based linkage maps for Prunus rootstocks. Here, we report on using a Genotyping-by-sequencing (GBS) approach to simultaneously discover and genotype SNPs from two peach rootstocks (‘Adafuel’ × ‘Flordaguard’) and their progeny. The plant material was developed at the EEAD-CSIC Prunus rootstocks breeding program with the goal to establish segregating progeny for a range of characters of importance to rootstock breeding (resistance to iron-chlorosis, root-asphyxia and replant diseases, as well as vigor and other effects on scions such as fruit quality and yield efficiency). High-density parental linkage maps were constructed by genotyping 118 siblings. Sequence reads obtained from GBS were aligned to the P. persica (L.) Batsch reference genome (Peach v2.0). A total of 18,912 high quality SNPs (MAF>0.05; missing data <5%), evenly distributed over the eight chromosomes, were identified. The number of identified SNPs ranged from 1,595 for the chromosome 7 to 4,042 for the chromosome 1. While eight linkage groups were constructed for ‘Adafuel’, only four linkage groups were constructed for ‘Flordaguard’, given the low heterozygosity of this genotype. High synteny and co-linearity was observed between obtained maps and Peach v2.0. These linkage maps of two phenotypically diverse Prunus rootstocks provide valuable information and will serve as the basis for identification of QTLs and genes relevant for Prunus rootstocks breeding.This work was funded by grants AGL2014-52063-R and INIA RFP 2015-00019, with FEDER and Gobierno de Aragón-A44 cofunding from Spain. It was also funded by CONICYTREGIONAL/GORE O´HIGGINS/CEAF/R08I1001, FONDECYT 3160316 and CONICYT R16F20006 from Chile. Carolina Font i Forcada is beneficiary of a Juan de la Cierva Incorporación 2017 contract.Peer reviewe

Phenotypic diversity among local Spanish and foreign peach and nectarine [Prunus persica (L.) Batsch] accessions

17 Pags., 7 Tabls., 1 Fig. The definitive version is available at: http://link.springer.com/journal/10681Phenotypic data for tree and fruit characteristics was collected over three consecutive years from a germplasm collection of 94 peach and nectarine accessions representing both traditional Spanish as well as foreign cultivars with widespread global plantings. All accessions were grown at the Experimental Station of Aula Dei located in the Ebro Valley (Northern Spain, Zaragoza) under a Mediterranean climate. Tree traits evaluated included bloom and harvest date, vigor, yield, yield efficiency and flower and leaf characteristics. Fruit traits included fresh weight, firmness, soluble solids, titratable acidity, levels of individual soluble sugars (sucrose, glucose, fructose and sorbitol), vitamin C, total phenolics, flavonoids, anthocyanins, relative antioxidant capacity and ripening index. Extensive variability was observed for most qualitative and quantitative traits with significant correlations identified between many traits. While the traditional Spanish accessions demonstrated good adaptability to the northern Spain evaluation site, opportunities for continued improvement in tree and fruit quality traits were demonstrated by an extensive phenotypic variability within the germplasm collection.This study was funded by the Spanish Ministry of Science and Innovation (MICINN) grants AGL2005-05533, AGL2008-00283 and AGL2011-24576, and RFP 2009-00016 cofunded by FEDER and the Regional Government of Aragon (A44). C. Font was supported by a JAE fellowship from Consejo Superior de Investigaciones Científicas (CSIC).Peer reviewe