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Genotyping-by-Sequencing (GBS) was applied in a set of 53 diploid Prunus rootstocks and five scion cultivars from three subgenera (Amygdalus, Prunus and Cerasus) for genome-wide SNP identification and to assess genetic diversity of both Chilean and Spanish germplasm collections. A group of 45,382 high quality SNPs (MAF >0.05; missing data <5%) were selected for analysis of this group of 58 accessions. These SNPs were distributed in genic and intergenic regions in the eight pseudomolecules of the peach genome (Peach v2.0), with an average of 53% located in exonic regions. The genetic diversity detected among the studied accessions divided them in three groups, which are in agreement with their current taxonomic classification. SNPs were classified based on their putative effect on annotated genes and KOG analysis was carried out to provide a deeper understanding of the function of 119 genes affected by high-impact SNPs. Results demonstrate the high utility for Prunus rootstocks identification and studies of diversity in Prunus species. Also, given the high number of SNPs identified in exonic regions, this strategy represents an important tool for finding candidate genes underlying traits of interest and potential functional markers for use in marker-assisted selection.

Background: To identify genotypes with good organoleptic properties, antioxidant-rich content and low susceptibility to chilling injury (CI), fruits from 130 peach cultivars were studied over three consecutive years. Pomological traits, l-ascorbic acid, flavonoids, total phenolics, relative antioxidant capacity (RAC) and sugars were determined. Major symptoms of CI developed at 5 °C, such as leatheriness, flesh browning, bleeding and loss of flavor, were evaluated., Results: The population exhibited wide phenotypic variation in agronomic and biochemical traits. Six genotypes with high total phenolics, RAC, flavonoids and total sugars were selected. The progeny also showed variability for all evaluated CI symptoms, and 16 genotypes showed considerably lower susceptibility to CI. After 2 weeks of cold storage, leatheriness and bleeding were the main CI symptoms observed, whereas flesh browning was predominant after 4 weeks., Conclusion: It was possible to find varieties with high phenolic concentration and relatively low or intermediate CI susceptibility (22, 33, 68, 80, 81, 96 and 120). However, the correlations observed between CI and phenolic contents highlight their potential influence on susceptibility to internal browning. This relationship should be considered in the current breeding programs to select cultivars with high bioactive compound contents, health-enhancing properties and good postharvest performance., (© 2014 Society of Chemical Industry.)

Two Prunus rootstocks, the Myrobalan plum P 2175 and the interspecific peach-almond hybrid, Felinem, were studied to characterize their biochemical and molecular responses induced under iron-Deficient conditions. Plants of both genotypes were submitted to different treatments using a hydroponic system that permitted removal of Fe from the nutrient solution. Control plants were grown in 90 μM Fe (III)-EDTA, Deficient plants were grown in an iron free solution, and plants submitted to an Inductor treatment were resupplied with 180 μM Fe (III)-EDTA over 1 and 2 days after a period of 4 or 15 days of growth on an iron-free solution. Felinem increased the activity of the iron chelate reductase (FC-R) in the Inductor treatment after 4 days of iron deprivation. In contrast, P 2175 did not show any response after at least 15 days without iron. The induction of the FC-R activity in this genotype was coincident in time with the medium acidification. These results suggest two different mechanisms of iron chlorosis tolerance in both Strategy I genotypes. Felinem would use the iron reduction as the main mechanism to capture the iron from the soil, and in P 2175, the mechanism of response would be slower and start with the acidification of the medium synchronized with the gradual loss of chlorophyll in leaves. To better understand the control of these responses at the molecular level, the differential expression of PFRO2, PIRT1 and PAHA2 genes involved in the reductase activity, the iron transport in roots, and the proton release, respectively, were analyzed. The expression of these genes, estimated by quantitative real-time PCR, was different between genotypes and among treatments. The results were in agreement with the physiological responses observed., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

Iron deficiency induces several responses to iron shortage in plants. Metabolic changes occur to sustain the increased iron uptake capacity of Fe-deficient plants. We evaluated the metabolic changes of three Prunus rootstocks submitted to iron chlorosis and their different responses for tolerance using measurements of metabolites and enzymatic activities. The more tolerant rootstocks Adesoto (Prunus insititia) and GF 677 (Prunus amygdalus×Prunus persica), and the more sensitive Barrier (P. persica×Prunus davidiana) were grown hydroponically in iron-sufficient and -deficient conditions over two weeks. Sugar, organic and amino acid concentrations of root tips were determined after two weeks of iron shortage by proton nuclear magnetic resonance spectroscopy of extracts. Complementary analyses of organic acids were performed by liquid chromatography coupled to mass spectrometry. The major soluble sugars found were glucose and sucrose. The major organic acids were malic and citric acids, and the major amino acid was asparagine. Iron deficiency increased root sucrose, total organic and amino acid concentrations and phosphoenolpyruvate carboxylase activity. After two weeks of iron deficiency, the malic, citric and succinic acid concentrations increased in the three rootstocks, although no significant differences were found among genotypes with different tolerance to iron chlorosis. The tolerant rootstock Adesoto showed higher total organic and amino acid concentrations. In contrast, the susceptible rootstock Barrier showed lower total amino acid concentration and phosphoenolpyruvate carboxylase activity values. These results suggest that the induction of this enzyme activity under iron deficiency, as previously shown in herbaceous plants, indicates the tolerance level of rootstocks to iron chlorosis. The analysis of other metabolic parameters, such as organic and amino acid concentrations, provides complementary information for selection of genotypes tolerant to iron chlorosis., (Copyright © 2010 Elsevier GmbH. All rights reserved.)

Epidemiological studies suggest that consumption of fruit rich in phenolic compounds is associated with health-protective effects due to their antioxidant properties. For these reasons quality evaluation has become an important issue in fruit industry and in breeding programs. Phytochemical traits such as total phenolics, flavonoids, anthocyanins, L-ascorbic acid, sugar content and relative antioxidant capacity (RAC) were analyzed over four years in flesh fruit of an F1 population "Venus" × "Big Top" nectarines. Other traits such as harvesting date, yield, fruit weight, firmness, soluble solids concentration (SSC), pH, titratable acidity (TA) and ripening index (RI) were also determined in the progeny. Results showed high variability among genotypes for all analyzed traits. Total phenolics and flavonoids showed significant positive correlations with RAC implying that both are important antioxidant bioactive compounds in peaches. We found genotypes with enhanced antioxidant capacity and a better performance than progenitors, and in consequence the best marketability.

Peaches and nectarines have a short shelf life even when harvested at appropriate physiological maturity. Market life is increased by storage at low temperatures. However, chilling injury symptoms can appear, causing physiological disorders and limiting shipping potential. The rootstock effect on the post-harvest quality has hardly been explored. Thus, the principal aim of this work was to study the influence of seven different Prunus rootstocks on the "Big Top" nectarine cv, considering harvest and post-harvest quality parameters and their correlation with chilling injury disorders. Basic fruit quality traits, individual sugars and organic acids analyzed by HPLC and other biochemical compounds such as relative antioxidant capacity, total phenolics content, flavonoids, anthocyanins, vitamin C and related enzyme activities (PAL, POD, PPO) were considered. In addition, correlations with possible candidate genes for chilling injury (CI) tolerance were searched by qPCR. Although a low susceptibility to CI symptoms has been found in "Big Top", rootstocks "PADAC 9902-01", "PADAC 99-05" and "ReplantPAC" exhibited lower CI symptoms. A statistically significant influence of the evaluated rootstocks was found concerning the parameters of this study. Phenols and anthocyanins seem to be important parameters to be considered in the prevention of chilling injury disorders. Moreover, PAL1, PPO4, PG2 and LDOX genes relative expressions were positively associated with chilling injury susceptibility. This study opens new perspectives for understanding peach fruit adaptation and response to cold storage temperatures during the post-harvest period. [ABSTRACT FROM AUTHOR]

Recent trends in peach orchards have focused on intensification and high density plantings using different Prunus rootstock species with different vigor traits. This investigation aims to study the physiological behavior of different Prunus rootstocks in order to identify the most suitable rootstock under warm Mediterranean conditions. Field agronomic performance and foliar nutrient content of the flat peach cultivar 'Subirana' grafted on ten different Prunus rootstocks were studied on calcareous soil typical of the Mediterranean area. Ten rootstocks: 'ADAGAF 04-03', 'AGAF 0301-04', 'Garnem', 'Krymsk® 1', 'Krymsk® 86', 'PAC 847', 'PADAC 04-01', 'PADAC 150', 'PM 105 AD', and 'Rootpac® 70', were considered. Vegetative growth, chlorophyll SPAD index, leaf mineral status and deviation from the optimum percentage (DOP) index were determined. Leaf chlorophyll content varied depending on the rootstock. 'PADAC 04-01' and 'ADAGAF 04-03' showed higher chlorophyll index. The lowest SPAD values were observed for the most dwarfing rootstock 'Krymsk® 1', which showed visual chlorosis symptoms, and lower leaf mineral contents compared to the other rootstocks. Peach trees on Prunus rootstocks showed differences in leaf macronutrient and micronutrient content. 'Rootpac® 70', 'ADAGAF 04-03' and 'PADAC 04-01' had better adaptation under warm Tunisian conditions but high ΣDOP index. The most invigorating 'Garnem' had the highest imbalanced nutritional status, but continues to perform well under warm conditions. Interesting results were obtained with 'Rootpac® 70' showing one of the best balanced nutritional values (average ΣDOP index). However, the most dwarfing rootstock 'Krymsk® 1' presented the worst adaptation to the studied warm Mediterranean conditions. [ABSTRACT FROM AUTHOR]

• A novel leaf disk assay discriminates between resistant and sensible stone fruit rootstocks to Pss infection. • A multi-tiered immune response is activated in Prunus rootstocks by Pss infection. • The mechanical wounding promotes the differential accumulation of callose in Prunus rootstocks. Bacterial canker, caused by Pseudomonas syringae pv syringae (Pss) , is a serious disease of stone fruit orchards causing severe yield reductions and the death of entire trees. To analyze the response and to identify novel sources of Pss resistance in our rootstock breeding program, we used a novel, rapid and reliable leaf disk pathogenicity test to screen pre-breeding material constituted by interspecific hybrids of plum/peach/almond ('AGAF'/'ADAGAF') or sweet cherry ('PACIR') species and commercial rootstocks with two Pss strains. Some 'AGAF'/ 'ADAGAF' and all 'PACIR' rootstocks showed lower susceptibility than commercial rootstocks to Pss strains used. The reduced symptoms displayed by the 'PACIR' hybrids with Prunus lannesiana and P. incisa as genomic background suggest that these species could be novel sources of genetic resistance to Pss within the Cerasus subgenus. Histological and candidate gene expression analysis suggest a multi-tiered immune response of Prunus species to Pss attack with a higher callose deposition and activation of molecular mechanisms that would restrict the bacteria infection and help to maintain a better redox homeostasis and performance of 'Marianna 2624′, a plum resistant genotype. Identification of Prunus species with resistance to Pss and the analysis of their immune response are the first step towards characterizing the underlying genetic mechanisms of resistance and introducing these traits into commercial germplasm. [ABSTRACT FROM AUTHOR]

Abstract: The field performance of fifteen peach and plum based rootstocks of different vigour (Adesoto, Evrica, Garnem, GF 677, HM-2, Krymsk® 1, PAC 9801-02, PAC 960, PAC 9907-02, PAC 9917-26, PAC-MUT, PADAC 9907-23, ROOTPAC® 40, ROOTPAC® 70 and Tetra) grafted with ‘Calrico’ cultivar was compared after 7 years of establishment on an Armillaria infested replant site. ‘Calrico’ is a selected clone of “Calanda” late peach cultivar. Differences in parameters such as tree survival, leaf chlorophyll content, vigour, yield, cumulative yield, yield efficiency and fruit size were analyzed among rootstocks. All PAC 9801-02 and Tetra trees survived and the mortality rate was low in Evrica, PADAC 9907-23 and ROOTPAC® 40. The rest of genotypes showed higher mortality rates. Leaf chlorophyll concentration was higher when grafted on Adesoto and Evrica and lower when grafted on PAC 9907-02 and PAC 9917-26. Garnem and PADAC 9907-23 were the most vigorous rootstocks. The highest yield efficiency was induced by Krymsk® 1 and PAC 9801-02 due to their lower vigour. The highest fruit weight was also induced by Krymsk® 1 but its cumulative yield was low. Other rootstocks that showed high fruit weight and cumulative yields were ROOTPAC® 70 and Tetra. Overall, Evrica, PAC 9801-02, ROOTPAC® 40 and Tetra were among the best adapted to soil sickness and calcareous soil showing a good agronomic performance. The first three rootstocks (Evrica, PAC 9801-02, ROOTPAC® 40) also exhibited a high capacity to control tree vigour associated with high yield efficiency. [Copyright &y& Elsevier]

Abstract: Twenty microsatellite primer pairs, previously developed in peach, were used to characterize and to explore genetic relationships among 44 clones, representing three groups of rootstocks defined as: (1) Peach-based rootstocks (Prunus dulcis × P. persica, P. persica × P. davidiana); (2) Myrobalan-Marianna plums (P. cerasifera and interspecific hybrids having P. cerasifera as a parent); and (3) Slow growing plums (P. insititia, P. domestica, and P. domestica × P. spinosa). Eighteen SSR markers, from the 20 initially used, were able to amplify polymorphic products for the Peach-based rootstocks and 13 common markers gave also polymorphism for the Myrobalan-Marianna and Slow growing plums groups. The Dice coefficient of similarity was calculated between all pairs of accessions and their genetic similarity represented by a principal coordinate analysis. The genetic diversity detected among the 44 clones studied divided them in three groups, which are in agreement with their current taxonomic classification and their morphological characteristics. A set of three microsatellites (BPPCT001, CPPCT022 and UDP98-407) can distinguish between all the clones analyzed. The analysis within groups reveal another two sets of three SSR to distinguish between the clones from the Peach based rootstocks and the Myrobalan-Marianna plums, respectively, and only a single SSR is needed to distinguish within the clones from the Slow growing plums group. These results demonstrate the high potential of the SSR analysis for peach rootstock identification and studies of diversity in Prunus species. [Copyright &y& Elsevier]