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Climate change is deeply impacting the food chain production, lowering quality and yield. In this context, the international scientific community has dedicated many efforts to enhancing resilience and sustainability in agriculture. Italy is among the main European producers of several fruit trees; therefore, national research centers and universities undertook several initiatives to maintain the specificity of the ‘Made in Italy’ label. Despite their importance, fruit crops are suffering from difficulties associated with the conventional breeding approaches, especially in terms of financial commitment, land resources availability, and long generation times. The ‘new genomic techniques’ (NGTs), renamed in Italy as ‘technologies for assisted evolution’ (TEAs), reduce the time required to obtain genetically improved cultivars while precisely targeting specific DNA sequences. This review aims to illustrate the role of the Italian scientific community in the use of NGTs, with a specific focus on Citrus, grapevine, apple, pear, chestnut, strawberry, peach, and kiwifruit. For each crop, the key genes and traits on which the scientific community is working, as well as the technological improvements and advancements on the regeneration of local varieties, are presented. Lastly, a focus is placed on the legal aspects in the European and in Italian contexts.

CRISPR/Cas9 genome editing is a modern biotechnological approach used to improve plant varieties, modifying only one or a few traits of a specific variety. However, this technology cannot be easily used to improve fruit quality traits in citrus, due to the lack of knowledge of key genes, long juvenile stage, and the difficulty regenerating whole plants of specific varieties. Here, we introduce a genome editing approach with the aim of producing citrus plantlets whose fruits contain both lycopene and anthocyanins. Our method employs a dual single guide RNA (sgRNA)-directed genome editing approach to knockout the fruit-specific β-cyclase 2 gene, responsible for the conversion of lycopene to beta-carotene. The gene is targeted by two sgRNAs simultaneously to create a large deletion, as well as to induce point mutations in both sgRNA targets. The EHA105 strain of Agrobacterium tumefaciens was used to transform five different anthocyanin-pigmented sweet oranges, belonging to the Tarocco and Sanguigno varietal groups, and ‘Carrizo’ citrange, a citrus rootstock as a model for citrus transformation. Among 58 plantlets sequenced in the target region, 86% of them were successfully edited. The most frequent mutations were deletions (from -1 to -74 nucleotides) and insertions (+1 nucleotide). Moreover, a novel event was identified in six plantlets, consisting of the inversion of the region between the two sgRNAs. For 20 plantlets in which a single mutation occurred, we excluded chimeric events. Plantlets did not show an altered phenotype in vegetative tissues. To the best of our knowledge, this work represents the first example of the use of a genome editing approach to potentially improve qualitative traits of citrus fruit.

Alternaria alternata is a fungus that causes a serious disease in susceptible genotypes of citrus, particularly in mandarins. The Alternaria citri toxin (ACT) produced by the pathogen induces necrotic lesions on young leaves and fruits, defoliation and fruit drop. Here, we describe two methods of marker-assisted selection (MAS) that could be used for the early identification of Alternaria brown spot (ABS)-resistant mandarin hybrids. The first method is based on a nested PCR coupled to high resolution melting (HRM) analysis at the SNP08 locus, which is located at 0.4 cM from the ABS resistance locus, and was previously indicated as the most suitable for the selection of ABS-resistant hybrids. The method was validated on 41 mandarin hybrids of the CREA germplasm collection, and on 862 progenies generated from five crosses involving different susceptible parents. Four out of five populations showed Mendelian segregation at the analyzed locus, while a population involving Murcott tangor as male parent showed distorted segregation toward the susceptible hybrids. The second method is based on a cleaved amplified polymorphic sequences (CAPS) marker that was developed using the same primers as the nested PCR at the SNP08 locus, coupled with BccI restriction enzyme digestion. To verify the reliability of the two genotyping methods, in vitro leaf phenotyping was carried out by inoculating A. alternata spores onto young leaves of 101 hybrids, randomly chosen among the susceptible and resistant progenies. The phenotyping confirmed the SNP08 genotyping results, so the proposed method of selection based on HRM or CAPS genotyping could be routinely used as an alternative to KBioscience competitive allele specific polymerase chain reaction (KASPar) single nucleotide polymorphism (SNP) genotyping system to improve citrus breeding programs. While the study confirmed that the SNP08 marker is a reliable tool for MAS of new citrus hybrids with different genetic backgrounds, it also identified a small group of genotypes where the resistance mechanism requires further investigation.

New plant breeding techniques (NPBTs) aim to overcome traditional breeding limits for fruit tree species, in order to obtain new varieties with improved organoleptic traits and resistance to biotic and abiotic stress, and to maintain fruit quality achieved over centuries by (clonal) selection. Knowledge on the gene(s) controlling a specific trait is essential for the use of NPBTs, such as genome editing and cisgenesis. In the framework of the international scientific community working on fruit tree species, including citrus, NPBTs have mainly been applied to address pathogen threats. Citrus could take advantage of NPBTs because of its complex species biology (seedlessness, apomixis, high heterozygosity, and long juvenility phase) and aptitude for in vitro manipulation. To our knowledge, genome editing in citrus via transgenesis has successful for induced resistance to Citrus bacterial canker in sweet orange and grapefruit using the resistance gene CsLOB1. In the future, NPBTs will also be used to improve fruit traits, making them healthier. The regeneration of plants following the application of NPBTs is a bottleneck, making it necessary to optimize the efficiency of current protocols. The strengths and weaknesses of using explants from young in vitro plantlets, and from mature plants, will be discussed. Other major issues addressed in this review are related to the requirement for marker-free systems and shortening the long juvenility phase. This review aims to summarize methods and approaches available in the literature that are suitable to citrus, focusing on the principles observed before the use of NPBTs.

Background: Anthocyanin pigmentation characterizes a number of tissues of Citrus and its relatives. The gain and loss of pigmentation is intriguing and is inherited variously among species. Methods: Citrus germplasm was used to investigate the anthocyanin pigmentation of tissues never before considered, including stamen, style and stigma, and of young leaves, petals, rind and flesh of 28 genotypes belonging to 14 species. Citrus genotypes encompassed citron, lemon, sweet orange, lime, and Citrus relatives included Microcitrus, Murraya, and Severinia. A relative qRT-PCR analysis was carried out on the structural and regulatory genes: phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3&prime, hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), uridine diphosphate glucose flavonoid glucosyl-transferase (UFGT), glutathione S-transferase (GST), Ruby and Noemi. Image analysis and a genomic approach were employed to evaluate how the red pigmentation is inherited among tissues and species. Results: Pigmentation of young leaves and petals is specific to citron and its hybrids. Ruby controls the pigmentation of petals, but not of leaves. The red color of the rind and flesh is a trait that particularly characterizes a diversity of sweet oranges, citron hybrids and Citrus relatives. Color expression depends on external factors and also on developmental stage. The coloration of stamen and style is citron-specific, while a red stigma is exclusive to Moro orange and its hybrids. Conclusion: It is hypothesized that there is a relationship among Citrus species and genes controlling anthocyanin pigmentation.

Background: Anthocyanin pigmentation characterizes a number of tissues of Citrus and its relatives. The gain and loss of pigmentation is intriguing and is inherited variously among species. Methods: Citrus germplasm was used to investigate the anthocyanin pigmentation of tissues never before considered, including stamen, style and stigma, and of young leaves, petals, rind and flesh of 28 genotypes belonging to 14 species. Citrus genotypes encompassed citron, lemon, sweet orange, lime, and Citrus relatives included Microcitrus, Murraya, and Severinia. A relative qRT-PCR analysis was carried out on the structural and regulatory genes: phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3′-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), uridine diphosphate glucose flavonoid glucosyl-transferase (UFGT), glutathione S-transferase (GST), Ruby and Noemi. Image analysis and a genomic approach were employed to evaluate how the red pigmentation is inherited among tissues and species. Results: Pigmentation of young leaves and petals is specific to citron and its hybrids. Ruby controls the pigmentation of petals, but not of leaves. The red color of the rind and flesh is a trait that particularly characterizes a diversity of sweet oranges, citron hybrids and Citrus relatives. Color expression depends on external factors and also on developmental stage. The coloration of stamen and style is citron-specific, while a red stigma is exclusive to Moro orange and its hybrids. Conclusion: It is hypothesized that there is a relationship among Citrus species and genes controlling anthocyanin pigmentation.

Plants have evolved a range of adaptive mechanisms that adjust their development and physiology to variable external conditions, particularly in perennial species subjected to long-term interplay with the environment. Exploiting the allelic diversity within available germplasm and leveraging the knowledge of the mechanisms regulating genotype interaction with the environment are crucial to address climatic challenges and assist the breeding of novel cultivars with improved resilience. The development of multisite collections is of utmost importance for the conservation and utilization of genetic materials and will greatly facilitate the dissection of genotype-by-environment interaction. Such resources are still lacking for perennial trees, especially with the intrinsic difficulties of successful propagation, material exchange, and living collection maintenance. This work describes the concept, design, and realization of the first multisite peach (Prunus persica) reference collection (PeachRefPop) located across different European countries and sharing the same experimental design. Other than an invaluable tool for scientific studies in perennial species, PeachRefPop provides a milestone in an international collaborative project for the conservation and exploitation of European peach germplasm resources and, ultimately, as a true heritage for future generations.

Cultivated apricot (Prunus armeniaca L.) is represented by a growing number of commercial cultivars featuring a wide variability of flesh texture and ripening evolution, affecting the entire chain from harvest to the final consumer. In order to establish fast and reliable tools easy applicable in the field to determine the harvest time, diverse commercial apricots were evaluated over 2 years for fruit ripening evolution by conventional and non-destructive methods. All fruit were harvested from a single tree at physiological ripening onset, then fruit were graded with a DA-meter® device, according to three ripening stages (physiological and commercial ripening, veraison), 30 fruit each. Fruit from each stage, after being scored by a near-infrared analyzer, were than randomly divided into three batches, each of which was subjected to standard ripening assessment: firmness (Fi) by using a digital penetrometer, soluble solids content (SSC) by using a digital refractometer, and total acidity (TA) by titration and pH measurement. Fi and SSC were assessed on both fruit sides, while TA and pH were determined on 10 homogenized fruits. The curves produced after optimization showed good predictability, particularly for TA, SSC and pH: R2 was 78.57, 79.17 and 80.56 (in cross-validation, respectively), despite the diversity of the assessed cultivars and the different stages of ripening. Some more work still has to be done to improve the predictability of Fi (R2=38.53), and further investigation has to be carried out to better fit the data from the penetrometer, or other devices measuring flesh texture. These results are to be considered as preliminary for the setting up of cultivar-specific harvest parameters.

The increase of peach (Prunus persica L. Batsch) fruit shelf-life is one of the most important objectives of breeding activities, as peach is a highly perishable fruit which undergoes rapid softening during ripening. The loss of fruit firmness is accompanied by a modification of textural properties. At least four distinct textures were described in peach: melting, non-melting, stony-hard, and slow-melting (better defined as "slow-softening"). Flesh textures are usually discriminated using different approaches, specific for each type. Objective of this work was the development of a reliable method to assess flesh texture variants in peach fruit, with special attention to the slow-softening type which is currently scored by sensorial evaluation. A puncture-based test using a digital penetrometer was performed on 20 accessions belonging to the four textural groups, obtaining a series of rheological measures related to mechanical flesh properties and including Young's Modulus, Upper Yield Point, and Slope of Yield Stress. Among the components of elasto-plastic behavior of the fruits, the texture dynamic index (TD) was shown to be a reliable parameter to distinguish the group of melting flesh texture from slow-softening, non-melting, and stony-hard, these last resulting characterized by similar mechanical properties. The TD index can be applied to discriminate slow-softening and melting fruits, although variability within the different texture groups suggests the existence of accessions with intermediate phenotypes and minor quantitative trait variation. The availability of an objective method to clearly distinguish the melting from the slow-softening phenotypes paves the road to phenotype segregating progenies in order to find molecular markers associated to the slow-softening trait. Practical applications The TD index could be considered to determine different textures in fleshy fruits in preharvest and postharvest, to support evaluation of quality for the intended use.

Non-structural carbohydrates provide the carbon and energy for plant growth and survival, being starch one of the main compounds accumulated in woody organs of trees. However, starch quantification in woody tissues is difficult and time consuming. Therefore, we hypothesized that reflectance spectroscopy could provide rapid and low cost methods to quantify carbohydrates in woody tissues. With this aim we analyzed the spectra of trunk tissues from different grapevine species (Vitis spp.) and results were compared to standard analyses. PLS regression appeared particularly performant for the elaboration and analysis of the collected spectra. This statistical approach produced high correlations with the concentrations of both starch and soluble sugars. To focus on starch detection, a specific on-solid colorimetric reaction was also proposed. Starch-iodine complexation produced significant modifications in spectral features.

Fruit texture is a crucial quality factor influencing consumer preference and shelf life. Peach (P. persica L. Batsch) is a highly perishable fruit subjected to a rapid softening after harvest. Improvement of peach shelf life is an important breeding objective, stimulating the characterization and exploitation of texture-related traits. Variants of melting (M) texture have captured an increasing interest, following the economic success of “Big Top” nectarine, one of the most cultivated varieties worldwide. “Big Top” fruit maintains a crispy texture for an extended period before the onset of the melting phase, prolonging its shelf life. Genetic determinants regulating this complex trait, defined as slow softening (SwS), are still unknown, mainly because of limitations in phenotyping methods. In this work, a mechanical approach for measuring SwS fruit texture was used to phenotype offspring derived from a cross between “Rebus028” (SwS texture) and “Max10” (M texture). Mechanical parameters were used in linkage mapping, allowing the identification of a major QTL on chromosome 8 (qSwS8.1). The presence of this QTL was validated by a genome-wide association study (GWAS) in a panel of accessions phenotyped for mechanical properties. Less significant signals were also detected by GWAS in other genomic regions, suggesting that additional loci may regulate the SwS trait, possibly depending on the genetic background. The inheritance pattern of the SwS trait and the presence of additional loci are crucial aspects to be addressed in future studies, along with a better characterization of other important textural attributes.

Double flowers with supernumerary petals have been selected by humans for their attractive appearance and commercial value in several ornamental plants, including Prunus persica (peach), a recognized model for Rosaceae genetics and genomics. Despite the relevance of this trait, knowledge of the underlying genes is limited. Of two distinct loci controlling the double-flower phenotype in peach, we focused on the dominant Di2 locus. High-resolution linkage mapping in five segregating progenies delimited Di2 to an interval spanning 150 858 bp and 22 genes, including Prupe.6G242400 encoding an euAP2 transcription factor. Analyzing genomic resequencing data from single- and double-flower accessions, we identified a deletion spanning the binding site for miR172 in Prupe.6G242400 as a candidate variant for the double-flower trait, and we showed transcript expression for both wild-type and deleted alleles. Consistent with the proposed role in controlling petal number, Prupe.6G242400 is expressed in buds at critical times for floral development. The indelDi2 molecular marker designed on this sequence variant co-segregated with the phenotype in 621 progenies, accounting for the dominant inheritance of the Di2 locus. Further corroborating the results in peach, we identified a distinct but similar mutation in the ortholog of Prupe.6G242400 in double-flower roses. Phylogenetic analysis showed that these two genes belong to a TARGET OF EAT (TOE)-type clade not represented in Arabidopsis, indicating a divergence of gene functions between AP2-type and TOE-type factors in Arabidopsis and other species. The identification of orthologous candidate genes for the double-flower phenotype in two important Rosaceae species provides valuable information to understand the genetic control of this trait in other major ornamental plants.

The aim of this research was to deepen the knowledge about the slow softening texture in peach. The texture is a synthesis of several parameters detected by senses, derived from the food structure. The paramount sense in the texture perception is the tactile one, principally perceived by hand and mouth. The tactile perception is a combination of four classes of mechanoreceptors, each one specialized to perceive mechanic deformation with different speed. This combined perception influences the consumer evaluation of food quality, giving the texture importance among food characteristics. The texture could also affect the taste perception through mechanical actions on food structure. The mechanical property linked to the texture is associated with the cellular organization and the cell wall strength. The main cell wall component affecting texture in fresh fruit is pectin, a polymer of galacturonic acid. The disassembly of pectin involves several enzymatic and non-enzymatic activities acting directly in pectin cleavage or indirectly disrupting non-covalent interactions. The gold standard of texture analyses is the sensorial one, however several issues make sensorial analyses inapplicable to breeding programs to select plant with improved fruit texture. Several efforts were made to achieve instrumental analyses capable of substitute humans in texture analyses. To mimic the tactile sense, a discipline studying the material response to an applied force, the rheology, is applied. The easiest instrumental measure of rheology parameters is the penetrometer test, diffused to measure the firmness, but exploitable to collect the Young?s modulus and the slope of yield stress represented respectively elasticity and fracturability. In peach, so far at least four textures were described, melting (M), stony hard (SH), non-melting (NM) and slow softening (SS). Prior to this work, no reliable objective nor fast tool were available to phenotype and select the SS trait in peach germplasm. The only reliable approach was a sensorial assessment done by a texture-trained panel, requiring repeated and time-consuming assessment. An objective, instrumental method, was set up by processing the data of a digital penetrometer test. The penetrometer itself, as reported in paragraph 2, does not support the ability to discriminate among the different texture types, as already reported in other works. In addition, this method appears to be affected by the fruit ripening season, since the early-ripening accessions tend to show faster loss of firmness, while the late-ripening exhibit a slower firmness loss. Using the data collected in our experiment, the texture dynamic (TD) model was developed from the observation of differences in the rheogram shape due to the elasticity and fracturability parameters. The TD model, that excludes the firmness effect on the fracturability and elasticity parameters, was thus developed, after testing it on 20 accessions in three years, allowing for reliable discrimination between SS and M phenotype. Differences in the TD were also found when comparing M vs SH and M vs NM textures. In particular, when comparing M and SS, TD value is explained for the 96% from the texture. The developed method was then applied (together with sensorial evaluation) to genetically dissect the SS trait. Association and QTL mapping approaches were combined by analyzing a germplasm panel and a biparental progeny, and a single locus at the end of chromosome 8 was identified. RNA-seq analysis of 2 SS and 2 M accessions suggested some common features with the SH type described in literature. In both texture types a lower auxin response was found when compared to the M type. This agrees with the already known activity of auxin in the modulation of cell wall rearrangement and expansion. Therefore, slower softening could be associated to slower cell wall rearrangement. In future, comparison of auxin content in slow softening and melting type peaches might provide further insight into the validity of this hypothesis. In detail, by RNA-seq comparing M and SS a total of 64 differentially expressed genes were found in the genomic region harboring the SS locus. Out of these 64 genes, 16 are uncharacterized, while among the characterized ones, 4 are putatively involved in auxin response based on peach genome annotation. Analysis of polymorphisms in these 4 DEGs based on resequencing data of the ?Max10? and ?Rebus 028? parents of biparental population did not uncover any variants in agreement with the observed segregation. Analyzing 2kb gene models flanking regions, 16 genes were associated with polymorphisms outside the coding sequence: the possible regulatory effects of such variants require further evaluation by expression analyses. In summary, the major results are the setup of a reliable tool to score objectively the SS texture and the detection of a major locus and his dominant mendelian inheritance. However, NGS and RNA-seq approaches are presented as a speculative data only, because they are not supported by hormones content in fruit, and the large locus detected did not allow indication of a putative variant. These results will: a) give impetus in exploring SS genetic and physiology; b) support the design of future crosses and experiments; c) increase marker density in the locus; d) point out the possible central role of auxin (to validate the hypothesis of a similarity between SS and SH physiology); e) allow texture assessment of improved cultivars; and f) allow phenotyping of segregating progenies to develop molecular markers associated with the SS trait.

Applying next-generation sequencing (NGS) technologies to species of agricultural interest has the potential to accelerate the understanding and exploration of genetic resources. The storage, availability and maintenance of huge quantities of NGS-generated data remains a major challenge. The PeachVar-DB portal, available at http://hpc-bioinformatics.cineca.it/peach, is an open-source catalog of genetic variants present in peach (Prunus persica L. Batsch) and wild-related species of Prunus genera, annotated from 146 samples publicly released on the Sequence Read Archive (SRA). We designed a user-friendly web-based interface of the database, providing search tools to retrieve single nucleotide polymorphism (SNP) and InDel variants, along with useful statistics and information. PeachVar-DB results are linked to the Genome Database for Rosaceae (GDR) and the Phytozome database to allow easy access to other external useful plant-oriented resources. In order to extend the genetic diversity covered by the PeachVar-DB further, and to allow increasingly powerful comparative analysis, we will progressively integrate newly released data.

Table S3. SRA accession number of assembled Illumina Whole-Genome libraries. (DOCX 13Â kb)

Table S4. List of candidate genes identified on the chromosome 6 region comprised between SNP_IGA_652659 (13,743,178Â bp) and SNP_IGA_534275 (15,609,595Â bp). (DOCX 17Â kb)

Table S2. List of primers used for quantitative PCR analyses. (DOCX 12Â kb)

Table S1. List of analyzed peach accessions and respective texture phenotype. (DOCX 19Â kb)

Together with stomatal conductance and root conductivity, the stem water reserve and transport systems could be regulatory mechanisms able to participate in the regulation of the plant water status. Lianas, such as Vitis spp., minimize the trunk support role, and stems have evolved to improve their ability in water transport. In this work, stems of 10 different Vitis species were studied in relation to their expected drought tolerance using reflectance spectroscopy. Spectra were measured before (T0) and after coloration with Sudan IV dye. The T0 spectral signature showed characteristic species features. The partial least squares (PLS) regression and the self-organizing map (SOM) neural network analysis were able to predict the expected drought tolerance score; thus, reflectance spectroscopy was demonstrated to be a useful technique for drought tolerance phenotyping. These methods could be applied for the preliminary selection of new rootstocks/cultivars. Wood composition variation appeared to be correlated with the water stress susceptibility. To clarify this relationship, the attention was focused on the wood hydrophobicity. Sudan IV is a microscopy dye traditionally used to underline suberin, waxes, and, in general, hydrophobic substances. Differences between rough and colored spectra evidenced the absorption band of Sudan IV with a maximum at 539 nm. The coloration intensity was used to develop a hydrophobicity index. The obtained values were correlated with the expected drought tolerance score. Therefore, hydrophobic compounds seem to play an important role in water use efficiency, and an hydrophobic barrier in the xylem tissue appears to be a protective mechanism against water stress.

Background Plum pox virus (PPV), agent of Sharka disease, is the most important quarantine pathogen of peach (P. persica L. Batsch). Extensive evaluation of peach germplasm has highlighted the lack of resistant sources, while suggesting the presence of a quantitative disease resistance, expressed as reduction in the intensity of symptoms. Unravelling the genetic architecture of peach response to PPV infection is essential for pyramiding resistant genes and for developing more tolerant varieties. For this purpose, a genome-wide association (GWA) approach was applied in a panel of accessions phenotyped for virus susceptibility and genotyped with the IPSC peach 9 K SNP Array, and coupled with an high-coverage resequencing of the tolerant accession ‘Kamarat’. Results Genome-wide association identified three highly significant associated loci on chromosome 2 and 3, accounting for most of the reduction in PPV-M susceptibility within the analysed peach population. The exploration of associated intervals through whole-genome comparison of the tolerant accession ‘Kamarat’ and other susceptible accessions, including the PPV-resistant wild-related species P. davidiana, allow the identification of allelic variants in promising candidate genes, including an RTM2-like gene already characterized in A. thaliana. Conclusions The present study is the first effort to identify genetic factors involved in Sharka disease in peach germplasm through a GWA approach. We provide evidence of the presence of quantitative resistant loci in a collection of peach accessions, identifying major loci and highly informative SNPs that could be useful for marker assisted selection. These results could serve as reference bases for future research aimed at the comprehension of genetic mechanism regulating the complex peach-PPV interaction. Electronic supplementary material The online version of this article (10.1186/s12870-017-1117-0) contains supplementary material, which is available to authorized users.

List of candidate genes identified on the chromosome 2 region associated to SNP_IGA_214703 (from 8.5 to 9.1Â Mb) (DOCX 9 kb)

List of primers used in this study. (DOCX 8 kb)

The last decade has been characterized by a decrease in peach (Prunus persica) fruit consumption in many countries, foremost due to unsatisfactory quality. The sugar content is one of the most important quality traits perceived by consumers, and the development of novel peach cultivars with sugar-enhanced content is a primary objective of breeding programs to revert the market inertia. Nevertheless, the progress reachable through classical phenotypic selection is limited by the narrow genetic bases of peach breeding material and by the complex quantitative nature of the trait, which is deeply affected by environmental conditions and agronomical management. The development of molecular markers applicable in MAS or MAB has become an essential strategy to boost the selection efficiency. Despite the enormous advances in ‘omics’ sciences, providing powerful tools for plant genotyping, the identification of the genetic bases of sugar-related traits is hindered by the lack of adequate phenotyping methods that are able to address strong within-plant variability. This review provides an overview of the current knowledge of the metabolic pathways and physiological mechanisms regulating sugar accumulation in peach fruit, the main advances in phenotyping approaches and genetic background, and finally addressing new research priorities and prospective for breeders.