Peach Rootstocks Research Articles

Screening Almond Rootstocks for Sources of Resistance to Armillaria Root Disease

Prunus dulcis (almond) is one of the most susceptible horticultural crops to Armillaria root disease. Resistance to Armillaria mellea and Armillaria tabescens, the geographically isolated causal fungi that attack almond and closely related Prunus persica (peach), has been evaluated in studies of almond, peach, and other Prunus rootstocks, but not in one comprehensive study. We evaluated the relative resistance to A. mellea and A. tabescens of six clonally propagated almond and peach rootstocks (Bright’s 5, Empyrean 1, Hansen 536, Krymsk 1, Krymsk 86, and Lovell) in comparison with that of clonally propagated Marianna 2624 rootstock (resistant control) and clonally propagated Nemaguard rootstock (susceptible control). Replicate clones used in the growth chamber assay were micropropagated and rooted in vitro before inoculating the culture medium with Armillaria spp. At 2 months, the most resistant and susceptible rootstocks were Krymsk 86 and Hansen 536, respectively, with 27% vs. 89% mortality. This finding was consistent among two isolates of A. mellea and one isolate of A. tabescens in three replicate experiments. Our finding of low mortality among Krymsk 86, Krymsk 1, and Marianna 2624, which all share Prunus cerasifera (Myrobalan plum) parentage, is consistent with past reports of resistance in the field to A. mellea, but conflicts with reports of susceptibility to A. tabescens. Resistance to A. tabescens of genotypes with Myrobalan plum parentage in our assay may reflect the simplified rooting environment of tissue culture medium, which does not perfectly mimic a field trial, in which biotic and abiotic factors may affect host resistance. Nonetheless, our growth chamber assay may provide a more rapid alternative to identify sources of resistance for breeding and to screen progeny of such crosses.

Rooting of herbaceous minicuttings of diff erent cultivars of peach rootstocks under the eff ect of IBA

The use of sexually propagated rootstocks is a major problem for peach crops in Brazil due to lack of plant homogeneity, which aff ects orchard production and longevity. To tackle the heterogeneity problem, clonal propagation is a promising alternative for the production of quality seedlings. There are few rootstocks options available in Brazil for stone fruit, and research work in this area is relatively recent. Therefore, this study aimed at assessing the technical feasibility of the propagation of some peach cultivars such as Capdeboscq, Aldrighi, Nemared, Nemaguard and Flordaguard, through herbaceous minicuttings. In addition, diff erent concentrations of IBA (0, 1.000, 2.000 and 3.000mg L-1) were tested. The minicuttings were immersed in a solution for fi ve seconds and, then, placed in a SANPACK® hinged clear plastic package for food, with 10x13x20cmof height, width and length, respectively, containing medium vermiculite. The experiment was conducted with four replications of 20 minicuttings, and kept in a greenhouse. At day 60, the rooting percentage, number and average length of the three longest roots, number and length of the longest rooting, and number and length of the longest shoot were evaluated. After the rooting period, the greatest rooting percentage for Capdeboscq cultivar was observed, with 74 %, using IBA concentrations of 2.000 and 3.000mgL-1.

Effectiveness of peach (Prunus persica) rootstocks for vigor control of plum (P. salicina) scions in relation with xylem vessel size

Effectiveness of peach (<i>Prunus persica</i>) rootstocks for vigor control of plum (<i>P. salicina</i>) scions in relation with xylem vessel size

Somaclonal variation in regenerated plants derived from callus of peach rootstocks

Somaclonal variation in regenerated plants derived from callus of peach rootstocks

Effect of tree architecture on fruit quality and yield attributes of nectarine (Prunus persica var. nectarina) cv. Fantasia under temperate condition

The present study was carried out at research farm of ICAR-Central Institute of Temperate Horticulture, Srinagar during the year 2009 to 2013. The nectarine cv. Fantasia grafted on wild peach rootstock and subsequently these trees were trained in six different training systems, viz. central leader system, open center system, Y shape- tatura trellis, four scaffolds, modified central leader system and modified open leader system. These six training systems were further evaluated for plant growth, fruit quality, and yield and average data of four years have been statistically analyzed. Significant chromatic variation was recorded for fruit skin color and maximum a* value was recorded in tatura trellis (44.13), similarly maximum trunk cross section area (TCSA) (54 cm2 ), fruit yield (32.72 tonnes/ha), fruit quality in terms of fruit weight (105.28 g), fruit length (65.53 mm), fruit diameter (66.85 mm), No. of fruits/plant (310) and yield efficiency (0.379 kg/cm2) were recorded in Y-shape tatura trellis system as compared to other traditional and contemporary tree architecture. Among biochemical parameters, highest TSS (14.66 0B) and ascorbic acid (15 mg/100g fresh fruit weight), titrable acidity (0.311%), TSS/acidity (60.89) was recorded in Y shape tatura trellis system, central leader system and modified open leader system respectively. Likewise total anthocyanin (6.23 mg cyanidin-3-glucoside equivalents 100/g fw), total carotenoids (8.71 mg/100 g), total phenols (575 mg GA equivalents/100 g), total flavonols (371 mg catechin equivalents /100 g), diphenyl-1-picryl hydrazyl (DPPH) (66 mg of AAE/100 g of fresh weight) and Ferric reducing antioxidant potential (FRAP) (69.16 mg of AAE /100 g of fresh weight) was recorded in Y shape tatura trellis followed by four scaffold training system. The present study emphasizes the superiority of Y shape tatura trellis system over other training system and could be exploited for higher quality and quantity nectarine production in temperate regions.

Short-term responses to flooding stress of three Prunus rootstocks

In fruit trees, flooding stress can affect plant survival and growth, and tolerance to root anoxia is determined by rootstock characteristics. Similarly to almond, peach trees are also among the Prunus species proving most susceptible to root anoxia in flooded soils. The aim of our study was to investigate the short-term responses to flooding of different Prunus rootstocks, in terms of growth and development and physiological variables. Flood treatments were continuously applied for 6days to myrobalan plum Sansavini 2/5 (Mr. S. 2/5), Monegro and Nemared peach rootstocks. Trees that were not exposed to flooding served as controls. Physiological and growth variables were evaluated. Flooding negatively affected net photosynthesis (Pn), leaf conductance (gs) and water potential (Ѱw) in Monegro and Nemared but not in Mr. S. 2/5 rootstock. However, flooding treatments did not affect the intercellular concentration of CO2 (Ci) in any of the rootstocks. We propose that the lack of alterations in Ci indicates that the processes related to photosynthetic metabolism are affected simultaneously with stomatal closure. Flooding only reduced the leaf growth of Monegro and Nemared rootstocks. The Mr. S. 2/5 rootstock had the highest constitutive root porosity, which increased its tolerance to flooding compared to the other rootstocks. The differences in the responses to flooding of various rootstocks should be considered in production settings where it is not possible to properly control irrigation to prevent short periods of flooding or in soils that do not drain irrigation or rain water quickly.

Mapping of new resistance (Vr2, Rm1) and ornamental (Di2, pl) Mendelian trait loci in peach

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’ × ‘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 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’®; 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.

Study on the red-leaf hybrid no. 9-205 as a rootstock for peach and nectarine cultivars

The aim of the present study was to establish the growth characteristics of the red-leaf peach hybrid No. 9-205, grown in a nursery, targeting its submission in future for recognition as a new vegetative rootstock for peach and nectarine cultivars. The traditional seedling rootstock 'Elberta' and the vegetative one GF-677 were included in the study. Hybrid No. 9-205 was selected from a population obtained at the Fruit- Growing Institute in Plovdiv by open pollination of Rutgers Red Leaf seedling rootstock for peach, used in the past. It is characterized by high drought resistance and good resistance to diseases and pests. It is easily propagated under in vitro conditions and shows weaker growth compared to GF-677 rootstock. 18 cultivar/rootstock combinations were studied, including two cultivars of each peach type: for fresh consumption, for processing and of the nectarine type. 'Laskava' cultivar for fresh consumption, the processing cultivar 'Spasena' and the cultivar 'Gergana', which is of the nectarine type, are newly established in result of the implementation of the breeding programme at the Fruit-Growing Institute - Plovdiv. They were officially recognized in the period 2009- 2012. The percentage of survival and of grafted bud shooting is high enough and meets the requirements of the production practices in nurseries. The planting material of the vegetative rootstock No. 9-205 is uniform in plant height and stem width and it fully complies with the quality standards.

Root Dynamics of Peach Replant Tolerant and Susceptible Rootstocks in Soilswith Different Cropping History

Replant disease (RD) is a major constraint for the establishment of economically viable tree fruit production systems. The use of tolerant rootstocks is considered the most cost-effective and long-term sustainable option to manage RD. The present study examines root production and lifespan of a replant tolerant and susceptible peach rootstock in a replant and non-replant soil. RD susceptible rootstock genotype Lovell and RD tolerant rootstock genotype Viking were established in a replant and non-replant site. Aboveground growth was determined by measuring the tree-trunk cross sectional area annually, and belowground root dynamics were tracked during a 2-year period using minirhizotron technology. Viking trees were significantly larger than Lovell in the replant site only. No significant differences were observed on the number of new roots produced by the two rootstocks in the replant or non-replant sites. In the replant site, roots of Viking remained white for a longer period of time, had higher AMF colonization, and second order roots had longer lifespans than those of Lovell rootstock; however no differences were observed between rootstocks in the non-replant site. Future research on identification of host defense mechanisms is needed for the development of tools that will support and accelerate breeding of resistant rootstocks.

Correlation of biometrical characteristics of fruit and seed with twinning and vigor of Prunus persica rootstocks

Abstract: This study aimed at determining and correlating the main morphometric characteristics of fruits and seeds with the germination potential and vigor of eight peach rootstocks. The experimental design was completely randomized, with four replications of 50 seeds per treatment. The analyzed variables were: length, width, thickness, fresh mass of fruit and seeds, moisture content of seeds, percentage of seeds attacked by fungi and intact seeds, germination percentage, germination speed index (GSI) and mean germination time (MGT). The Capdeboscq, Aldrighi and Tsukuba 1 cultivars showed higher values of length, width, thickness and fresh mass of seeds compared to other cultivars, presenting a relationship with the later period of fruit ripening. Regardless of the fruit ripening time, the germination percentage was high, ranging between 93% and 100% for all cultivars. In addition, the fresh mass of fruits has showed a high positive correlation with the fresh mass of seeds for the eight evaluated peach rootstocks. The GSI and MGT have a high relationship with the fresh mass of seeds.

Assessment of various Peach rootstocks for germination and seedling growth

Peach root stocks “Swat local”, “Chitral local” and “Okinawa” were evaluated to assess their performance in nursery at Agricultural Research Institute Mingora, Swat Pakistan during 2013`14. Days to germination, percent seed germination, seedling diameter, number of branches per seedling, number of leaves per seedlings and seedling height were found significant in all the three rootstocks. The indigenous root stock “Swat local” and “Chitral local” performed well for the aforementioned traits. The rootstock “Okinawa” had earlier germination.

Identification and characterization of endophytic bacteria isolated from in vitro cultures of peach and pear rootstocks.

Endophytes are microorganisms which live symbiotically with almost all varieties of plant and in turn helping the plant in a number of ways. Instead of satisfactory surface sterilization approaches, repeatedly occurring bacterial growth on in vitro rootstock cultures of peach and pear was identified and isolated as endophytic bacteria in our present study. Five different isolates from peach rootstocks were molecularly identified by 16S rRNA gene sequencing as Brevundimonas diminuta, Leifsonia shinshuensis, Sphingomonas parapaucimobilis Brevundimonas vesicularis, Agrobacterium tumefaciens while two endophytic isolates of pear were identified as Pseudoxanthomonas mexicana, and Stenotrophomonas rhizophilia. Identified endophytes were also screened for their potential of plant growth promotion according to indoleacetic acid (IAA) production, nitrogen fixation, solubilization of phosphate and production of siderophore. All seven endophytic isolates have shown positive results for IAA, nitrogen fixation and phosphate solubilization tests. However, two out of seven isolates showed positive results for siderophore production. On the basis of these growth promoting competences, isolated endophytes can be presumed to have significant influence on the growth of host plants. Future studies required to determine the antimicrobial susceptibility profile and potential application of these isolates in biological control, microbial biofertilizers and degradative enzyme production.

Performance of ‘Subirana’ flat peach cultivar budded on different Prunus rootstocks in a warm production area in North Africa

The agronomic performance and fruit quality traits were evaluated for ten Prunus rootstocks: Garnem, PADAC 150, PADAC 04-03, PADAC 04-01, Rootpac® 70, PM 105 AD, AGAF 0301-04, Krymsk® 1, Krymsk® 86 and PAC 847. These rootstocks were budded with ‘Subirana’ flat peach cultivar in September 2007 and planted in two adjacent plots in northern Tunisia (36°41′N, 10°15′E) on a heavy and calcareous soil typical of the Mediterranean area. Tree mortality, vegetative growth, rate of bud failure and fruit quality were assessed. Significant differences were found among rootstocks for the agronomic and fruit quality traits. Growing conditions generated varying levels of tree mortality, the highest with Krymsk® 1 rootstock. In contrast, all trees on PADAC 04-03 and PADAC 04-01 survived well. The lowest vigor was induced by Krymsk® 1 with a reduction of 90% in trunk cross-sectional area (TCSA) and canopy volume as compared to Garnem. PADAC 150 also expressed a low vigor. The highest canopy volume was found on Rootpac® 70 as similarly for Garnem. The remaining rootstocks induced a medium vigor level. Trees on vigorous rootstocks as Rootpac® 70 showed the lowest rate of bud failure, while dwarfing rootstocks induced the highest buds abscission. Yield was higher for AGAF 0301-04 in 2011 and 2012 as compared to the rest of rootstocks. The highest yield efficiency was recorded on PM 105 AD and AGAF 0301-04 rootstocks. Rootpac® 70 presented the highest fruit weight and fruit diameter. The highest level of soluble solids content (SSC) was recorded on Krymsk® 1, and the lowest on Garnem, although differences were not significant when compared to the other rootstocks. The less vigorous rootstocks seem to induce a better fruit quality of peach based on fruit sugar content. This study provides information that new Prunus rootstocks for peach can lead to a better agronomic performance than Garnem, mainly in vigor and in productive parameters. The peach-plum hybrid PADAC 04-03 induced good yield, with large fruit size and acceptable efficiency with significant smaller trees than Garnem.

Identification of Meloidogyne Species from the Central Valley of Chile and Interaction with Stone Fruit Rootstocks.

Root-knot nematodes (RKN; Meloidogyne spp.) are predominant polyphagous pests of crops in the Central Valley of Chile. Twenty RKN populations from this region were collected from diverse crops and subsequently identified with both sequence-characterized amplified region and isoenzyme markers. Populations included three RKN species: Meloidogyne ethiopica (75%), M. javanica (15%), and M. arenaria (10%). This is the first report of the high prevalence and wide host range of M. ethiopica in Chile. The host status of three Prunus rootstocks for isolates obtained from the Chilean RKN populations was then evaluated. Rootstocks assessed included the peach rootstock Nemaguard and the plum rootstock Marianna 2624, both previously considered resistant, and the peach rootstock Pomona as a susceptible accession. In the first experiment, rootstocks were inoculated individually in pots with 10,000 second-stage juveniles and eggs of each isolate, and reproduction and galling were evaluated 5 months after inoculation. In the second experiment, the six most aggressive RKN isolates were used in a mixture to evaluate the host response of the same three rootstocks. No RKN were detected on Marianna 2624 in both experiments, which confirmed its immune host status to M. arenaria and M. javanica; this is the first report of immunity to M. ethiopica. Even though Pomona was classified overall as susceptible, the response of this rootstock to the RKN isolates was highly variable and ranged from susceptible to resistant, depending on the RKN isolates. Nemaguard ranged from resistant (to each of the most aggressive isolates and to their mixture) to highly resistant (to M. arenaria isolates). Our results illustrate that Prunus rootstocks express different levels of resistance to RKN species. RKN resistance may be active either at the isolate level (as in Pomona), at the species level (as in Nemaguard toward M. javanica and M. arenaria), or at the genus level (as in Marianna 2624).

Genetic transformation of peach rootstock and cultivar to induce resistance against PPV virus through post-transcriptional gene silencing

Prunus, in particular peach, is considered one of the most recalcitrant species for what concerns in vitro regeneration, especially when the starting plant material originates from mature tissues. Furthermore, in terms of peach genetic transformation, few examples exist in literature and most of them demonstrate the difficulty in obtaining stable transformants. The present study describes an efficient method of in vitro regeneration, via organogenesis, starting from meristematic bulk tissues, characterized by a high competence to produce adventitious shoots and useful for genetic transformation of Prunus persica cultivar 'Big Top® Zaitabo*' and rootstock GF677. This protocol constitutes one of the few examples of peach in vitro regeneration starting from adult tissue present in the literature. It has been used to genetically transform the rootstock GF677 and the cultivar 'Big Top® Zaitabo*', through the development of two different methods of transformation, one mediated by Agrobacterium tumefaciens, applied on slices from meristematic bulk, and the other by the biolistic technique applied on slices from meristematic bulks and on vegetative apex. The transformation experiments were conducted using hairpin genetic constructs for the induction of Plum pox virus (PPV) resistance through the mechanism of post-transcriptional gene silencing (PTGS). To our knowledge, this is the first example of a successful attempt of a peach rootstock and cultivar stable genetic transformation and it represents a good promise for the future production of silenced GF677 plants to be tested for the capacity to induce PPV resistance also in the grafted scion.

Root Distribution of Peach Rootstocks Affected by Soil Compaction and Acidity

Root growth can be limited by physical and chemical conditions of the soil. Compacted and acidic soils, where there is an occurrence of exchangeable Al, constitute barriers to use of the soil by plant roots. The hypothesis of this study was that physical and chemical properties of the inter-row soil of a peach orchard influence the root distribution of different rootstocks. The aim of this study was to describe and register the soil physical and chemical properties and root distribution in the soil profile of the inter-row of seven years old mature peach (Prunus persica) orchard. Samples of soil (classified as an Argissolo Vermelho Distrofico tipico [Rhodic Paleudult] with 180 g kg-1 clay, 120 g kg-1 silt, and 700 g kg-1 sand) and roots were collected from orchard inter-rows of ‘Maciel’ peach, grafted onto ‘Okinawa’ and ‘Nemaguard’ rootstock, at 1.5, 2.0, and 2.5 m from the trunk, and at every 0.10 m, up to a depth of 0.50 m. The soil samples were sieved and the roots washed. A subsample was removed from each sample for chemical analysis. Resistance to penetration (RP) was used as an indicator of soil compaction. A close relationship was found among chemical properties, RP, and root distribution. Root density was affected by the presence of compacted regions (RP >2,000 kPa) and by high Al saturation in the exchange complex in the soil profile. There was a reduction in the frequency of thick roots (O >2 mm) in the samples collected in portions of compacted soil and at increasing soil depth. The compacted portion of the inter-row limits lateral distribution of the peach tree root system, while aluminum limits its depth.

Effect of Biochar Amendments on Peach Replant Disease

The use of biochar as a soil amendment has generated interest all over the world, and it has been advocated as a means to improve soil fertility and sequester carbon. The objective of this study was to test if the use of pinewood biochar could reduce the detrimental effects of replant disease (RD) on peach tree growth and biomass production. An RD-susceptible peach rootstock, Lovell, was grown in soil from a peach replant site (control), sterilized soil (sterilized), and biochar-amended soil at 10% and 20% (v/v) [low biochar (LB) and high biochar (HB), respectively], all from the same site. Trunk diameter increase was measured weekly; total aboveground and belowground biomass was determined by harvesting a subsample of plants at 11, 22, and 33 weeks after planting. Soil samples, and foliar and root tissue samples were collected before each harvesting date and analyzed for nutrient content. Total aboveground and belowground biomass production was significantly higher in the biochar and sterilized soil treatment (S) compared with the control. Root carbon (C*) content was significantly greater in the HB treatment compared with the control. Soil nitrate-N was significantly greater in the HB treatment by the third harvesting date, and foliar magnesium (Mg) concentrations were significantly higher in both biochar treatments for all harvesting dates. The results from this study provide evidence that biochar may alleviate RD in peach trees.

Detection of a New Luteovirus in Imported Nectarine Trees: A Case Study to Propose Adoption of Metagenomics in Post-Entry Quarantine.

In spring 2013, 5-year-old nectarine (Prunus persica) trees, grafted on peach rootstock Nemaguard, were found stunted in a propagation block in California. These trees had been propagated from budwood of three nectarine cultivars imported from France and cleared through the post-entry quarantine procedure. Examination of the canopy failed to reveal any obvious symptoms. However, examination of the trunks, after stripping the bark, revealed extensive pitting on the woody cylinder. To investigate the etiological agent, double-stranded RNA was extracted from bark scrapings from the scion and rootstock portions, and a cDNA library was prepared and sequenced using the Illumina platform. BLAST analysis of the contigs generated by the de novo assembly of sequence reads indicated the presence of a novel luteovirus. Complete sequence of the viral genome was determined by sequencing of three overlapping cDNA clones generated by reverse transcription-polymerase chain reaction (RT-PCR) and by rapid amplification of the 5'- and 3'-termini. The virus genome was comprised of 4,991 nucleotides with a gene organization similar to members of the genus Luteovirus (family Luteoviridae). The presence of the virus, tentatively named Nectarine stem pitting-associated virus, was confirmed in symptomatic trees by RT-PCR. Discovery of a new virus in nectarine trees after post-entry quarantine indicates the importance of including (i) metagenomic analysis by next-generation sequencing approach as an essential tool to assess the plant health status, and (ii) examination of the woody cylinders as part of the indexing process.

USE OF PRUNUS GENETIC DIVERSITY FOR PEACH ROOTSTOCKS

In the Redher classification, the most widely adopted classification of Prunus L., there are more than 200 species divided into five subgenera with three for the stone fruits: Amygdalus, Prunophora and Cerasus. The major peach rootstocks are included in the subgenera Amygdalus (peach and almond species), mainly because there are no or very few problems of incompatibility grafting. Currently, the peach seedlings that are easy to produce and productive, are often used as peach rootstock, except in the calcareous soils where peachxalmond hybrids are preferred. Prunophora species are chosen for a better adaptability to heavy soils, or for introducing resistance genes to nematodes, to fungus or bacterial soil-diseases. The grafting of Prunophora species induces lower vigor for Amygdalus species and can initiate more problems of grafting-incompatibility. So, a breeding program which integrates Prunophora species will be longer in time than one using only Amygdalus species. The main selected traits in the world peach rootstock breeding programs worldwide are still nematode resistance, waterlogging, vigor control, calcareous soils, and drought. For each trait, several Prunus genotypes may fit the requested characteristics, and it is important to choose the best crossing strategy which allows the breeder to obtain the best performance for all traits in order to replace an existing rootstock.

THE INFLUENCE OF VARIOUS ROOTSTOCKS FOR PEACH (PRUNUS PERSICA L.) ON PHENOLIC CONTENT AT GRAFTING POINT

The influence of various rootstocks for peach [Prunus persica (L.) Batsch] on the phenolic content in the phloem above and below the graft union was investigated, based on the role of phenols in graft incompatibility. Assays of phloem with cambium from 7-year-old peach trees of ‘Royal Glory’ cultivar, which were grafted on different rootstocks (‘GF 677’, peach seedling, ‘Monegro’, ‘Barrier’, ‘Cadaman’, ‘Penta’ and ‘Tetra’) were analysed with HPLC-MS. The most abundant phenolic compound in phloem above and below the graft union was the flavanols. The ‘Royal Glory’ cultivar was highly compatible with peach seedling, ‘GF 677’ and ‘Monegro’ rootstocks. In ‘Cadaman’ rootstock (Prunus persica A— Prunus davidiana), accumulation of flavonols was observed, and in ‘Barrier’ rootstock (Prunus persica A— Prunus davidiana), accumulation of flavanon was observed, in both cases above the graft union, which is related to graft incompatibility. Hydoxycinnamic acids were present only in plum rootstocks. The levels of flavonols and flavanols were significantly higher above the graft union at Prunus domestica rootstocks, which indicates that also flavonols could be involved in the graft incompatibility process.