Search

Phenolic and triterpenoid compounds are essential components in stone fruit skin and flesh tissues. They are thought to possess general antimicrobial activity. However, regarding brown rot disease, investigations were only confined to a limited number of phenolics, especially chlorogenic acid. The activity of triterpenoids against Monilinia spp., as an essential part of the peach cuticular wax, has not been studied before. In this work, the anti-fungal effect of some phenolics, triterpenoids, and fruit surface compound (FSC) extracts of peach fruit at two developmental stages were investigated on Monilinia fructicola and Monilinia laxa characteristics during in vitro growth. A new procedure for assaying anti-fungal activity of triterpenoids, which are notoriously difficult to assess in vitro because of their hydrophobicity, has been developed. Measurements of colony diameter, sporulation, and germination of second-generation conidia were recorded. Furthermore, the expression of twelve genes of M. fructicola associated with germination and/or appressorium formation and virulence-related genes was studied relative to the presence of the compounds. The study revealed that certain phenolics and triterpenoids showed modest anti-fungal activity while dramatically modulating gene expression in mycelium of M. fructicola on culture medium. MfRGAE1 gene was overexpressed by chlorogenic and ferulic acids and MfCUT1 by betulinic acid, at 4- and 7- days of mycelium incubation. The stage II FSC extract, corresponding to the period when the fruit is resistant to Monilinia spp., considerably up-regulated the MfLAE1 gene. These findings effectively contribute to the knowledge of biochemical compounds effects on fungi on in vitro conditions., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2023 British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Background: Texture is one of the most important fruit quality attributes. In peach, stony hard (SH) is a recessive monogenic trait (hd/hd) that confers exceptionally prolonged firm flesh to fully ripe fruit. Previous studies have shown that the SH mutation affects the fruit ability to synthesize appropriate amounts of indol-3-acetic acid (IAA), which orchestrates the ripening processes through the activation of system 2 ethylene pathway. Allelic variation in a TC microsatellite located within the first intron of PpYUC11-like (a YUCCA-like auxin-biosynthesis gene) has been recently proposed as the causal mutation of the SH phenotype., Results: The simple genetic determinism of the SH trait has been clarified through genome-wide association and LD analyses in a diverse set of accessions, restricting the hd locus to an interval of about 1.8 Mbp in chromosome 6. The comparison of fruit transcriptome data from non-SH (melting flesh) and SH accessions provided an expression patterns overview of the annotated transcripts within the hd locus, confirming the absence of PpYUC11-like expression in SH fruits. To explore further possible associations between genomic variants at the hd locus and the SH phenotype, re-sequencing data of the SH accession 'D41-62' were compared with several SH and non-SH accessions with different genetic backgrounds. A further step of validation was provided through the evaluation of variant-trait association in two bi-parental F 2 populations issued from the SH accession 'D41-62' and a panel of advanced breeding selections, showing perfect co-segregation of the PpYUC11-like intron TC 20 allele and the SH phenotype., Conclusions: In this study, we provide a multi-level validation of the genetic control of the SH trait through the integration of genome-wide association mapping, transcriptome analysis and whole-genome resequencing data for SH and non-SH accessions, and marker-trait association in a panel of advanced breeding selections and segregating progenies. Collectively, our data confirm with high confidence the role of allelic variation at PpYUC11-like locus as the genetic determinant of the SH trait, opening interesting perspectives at both biological and applied research level.

Background: Highly polygenic traits such as fruit weight, sugar content and acidity strongly influence the agroeconomic value of peach varieties. Genomic Selection (GS) can accelerate peach yield and quality gain if predictions show higher levels of accuracy compared to phenotypic selection. The available IPSC 9K SNP array V1 allows standardized and highly reliable genotyping, preparing the ground for GS in peach., Results: A repeatability model (multiple records per individual plant) for genome-enabled predictions in eleven European peach populations is presented. The analysis included 1147 individuals derived from both commercial and non-commercial peach or peach-related accessions. Considered traits were average fruit weight (FW), sugar content (SC) and titratable acidity (TA). Plants were genotyped with the 9K IPSC array, grown in three countries (France, Italy, Spain) and phenotyped for 3-5 years. An analysis of imputation accuracy of missing genotypic data was conducted using the software Beagle, showing that two of the eleven populations were highly sensitive to increasing levels of missing data. The regression model produced, for each trait and each population, estimates of heritability (FW:0.35, SC:0.48, TA:0.53, on average) and repeatability (FW:0.56, SC:0.63, TA:0.62, on average). Predictive ability was estimated in a five-fold cross validation scheme within population as the correlation of true and predicted phenotypes. Results differed by populations and traits, but predictive abilities were in general high (FW:0.60, SC:0.72, TA:0.65, on average)., Conclusions: This study assessed the feasibility of Genomic Selection in peach for highly polygenic traits linked to yield and fruit quality. The accuracy of imputing missing genotypes was as high as 96%, and the genomic predictive ability was on average 0.65, but could be as high as 0.84 for fruit weight or 0.83 for titratable acidity. The estimated repeatability may prove very useful in the management of the typical long cycles involved in peach productions. All together, these results are very promising for the application of genomic selection to peach breeding programmes.

Unlabelled: The nondestructive assessment of apricot fruit quality (Bora cultivar) was carried out by means of FT-NIR reflectance spectroscopy in the wavenumber range 12000 to 4000 cm⁻¹. Samples were harvested at four different ripening stages and scanned by a fiber optical probe immediately after harvesting and after a storage of 3 d (2 d at 4 °C and 1 d at 18 °C); the flesh firmness (FF), the soluble solids content (SSC), the acidity (A), and the titratable acidity (malic and citric acids) were then measured by destructive methods. Soft independent modeling of class analogy (SIMCA) analysis was used to classify spectra according to the ripening stage and the storage: partial least squares regression (PLS) models to predict FF, SSC, A, and the titratable acidity were also set-up for both just harvested and stored apricots. Spectral pretreatments and wavenumber selections were conducted on the basis of explorative principal component analysis (PCA). Apricot spectra were correctly classified in the right class with a mean classification rate of 87% (range: 80% to 100%). Test set validations of PLS models showed R2 values up to 0.620, 0.863, 0.842, and 0.369 for FF, SSC, A, and the titratable acidity, respectively. The best models were obtained for the SSC and A and are suitable for rough screening; a lower power prediction emerged for the other maturity indices and the relative predictive models are not recommended., Practical Application: The results of the study could be used as a tool for the assessment of the ripening stage during the harvest and the quality during the postharvest storage of apricot fruits.

Background: Volatile compounds, together with sugars and acids, are the main chemical species determining the characteristic aroma and flavor of food. In peach, more than 100 volatiles have been identified., Results: The essential oil of six peach and three nectarine accessions used in Italian breeding programs was obtained by steam distillation, and the volatiles were investigated. A total of 47 known volatiles, two unidentified compounds and nine hydrocarbons were identified, including 12 aldehydes, six alcohols, three acids, three esters, six terpenes, two phenylalanine derivates, two C(13) norisoprenoids, one ketone (C(9)) and 10 lactones. A wide variation in the number of volatiles and in their concentration was observed among the nine accessions. Twenty-one compounds presented odor activity values (OAVs) higher than 1 in at least one of the accessions and were therefore putatively considered as key odorants in the peach volatile composition., Conclusion: This study reports the identification, quantification and potency, based on the OAVs, of the most important volatile compounds, along with fruit quality characteristics, of nine different peach/nectarine accessions and will help future peach volatile breeding programs for the selection of odor-rich accessions to be used in the development of new improved cultivars.

Apricot breeding programs could be strongly improved by the availability of molecular markers linked to the main fruit quality traits. Fruit acidity is one of the key factors in consumer acceptance, but despite its importance, the molecular bases of this trait are still poorly understood. In order to increase the genetic knowledge on the fruit acidity, an F1 apricot population ('Lito' × 'BO81604311') has been phenotyped for titratable acidity and juice pH for the three following years. In addition, the contents of the main organic acids of the juice (malate, citrate, and quinate) were also evaluated. A Gaussian distribution was observed for most of the traits in this progeny, confirming their quantitative inheritance. An available simple sequence repeat (SSR)-based molecular map, implemented with new markers in specific genomic regions, was used to perform a quantitative trait loci (QTL) analysis. The molecular map was also anchored to the recently published apricot genome sequence of 'Stella.' Several major QTLs linked to fruit acidity-related traits have been identified both in the 'Lito' (no. 21) and 'BO81604311' (no. 13), distributed in five linkage groups (LG 4, 5, 6, 7, and 8). Some of these QTLs show good stability between years and their linked markers were used to identify candidate genes in specific QTLs genomic regions. [ABSTRACT FROM AUTHOR]

Fruit size and shape are critical agronomical and pomological attributes and prime targets in peach breeding programs. Apart from the flat peach type, a Mendelian trait well-characterized at the genetic level, ample diversity of fruit size and shapes is present across peach germplasms. Nevertheless, knowledge of the underlying genomic loci remains limited. In this work, fruit size and shape were assessed in a collection of non-flat peach accessions and selections, under controlled fruit load conditions. The architecture of these traits was then dissected by combining association and linkage mapping, revealing a major locus on the proximal end of chromosome 6 (qSHL/Fs6.1) explaining a large proportion of phenotypic variability for longitudinal shape and also affecting fruit size. A second major locus for fruit longitudinal shape (qSHL5.1), probably also affecting fruit size, was found co-localizing at locus G, suggesting pleiotropic effects of peach/nectarine traits. An additional QTL for fruit longitudinal shape (qSHL6.2) was identified in the distal end of chromosome 6 in a cross with an ornamental double-flower peach and co-localized with the Di2 locus, controlling flower morphology. Besides assisting breeding activities, knowledge of loci controlling fruit size and shape paves the way for more in-depth studies aimed at the identification of underlying genetic variant(s). [ABSTRACT FROM AUTHOR]

• Fruit quality features and organic acids contents greatly varied among the apricot cultivars and breeding selections. • Malate and citrate were the most abundant organic acids. • Sweet-sour taste perception was mostly affected by fruit titratable acidity level. • Citrate taste intensity strongly impacted the eating pleasantness of apricot drupes. • The detailed phenotypic characterization of apricot fruits might assist the definition of selection criteria in breeding novel varieties. Understanding the relationship between composition and taste is of pivotal importance for fruit quality improvement. This study aims to shed a light on the complex relationship between apricot fruit composition (both flesh and skin) and sensory perception. For this purpose, a total of 23 between apricot cultivars and breeding selections were characterized for a range of fruit-quality-related traits (maturity date, fresh weight, flesh firmness, soluble solids content, titratable acidity and total polyphenols content) and ten organic acids pattern in both flesh and skin. Fruit analytical data were correlated to sensory intensity through a detailed evaluation performed by ten trained panelists', with a particular focus on the impact of malate and citrate content on taste and acidity perception. Malate and citrate account for the 95% of the whole organic acids, although their content and ratio widely varied across the evaluated accessions (range of 0.96 – 14.05 and 0.33 – 20.08, respectively). Sweet-sour taste perception was greatly predicted by soluble solids content in apricots flesh (correlation of 0.60), but even more affected by titratable acidity (correlation between -0.84 and -0.97). In turn, titratable acidity was the main responsible of sour taste (correlation of 0.76) where citrate taste intensity (correlation up to 0.42) was stronger than malate in both fruit flesh and skin, with a negative effect on eating pleasantness. Results confirmed the importance of combining objective and sensory analyses to adequately comprehend apricot fruit quality. Moreover, the results corroborated the complexity of features defining the apricot fruit taste. This study provides novel insights into fruit quality- criteria to be considered in both breeding purposes and consumer's satisfaction-driven selection procedures. [ABSTRACT FROM AUTHOR]

• First characterization of 'Chinotto di Savona' at both the morphological and genetic level. • Fruit acidity and seedlessness feature the most interesting traits of this Citrus accession. • 'Chinotto di Savona' has originated from somatic mutations of sour orange (C. aurantium). • Both chinotto accessions have diploid genomes comparable in size to sour orange. For a long time 'Chinotto di Savona', a Citrus tree cultivated in Liguria region (northern Italy), has been considered a variety of Citrus myrtifolia (known with the Italian name 'chinotto'). Nevertheless, molecular analysis to address its true genetic origin has been not performed yet. Fruits of 'Chinotto di Savona' are highly appreciated and often preferred to common chinotto for its superior organoleptic characteristics by food and beverage industries. This work reports a first morphological and genetic characterization of 'Chinotto di Savona' aiming at inferring its origin and main pomological traits. The main phenotypic characteristics of this Citrus accession were also evaluated and compared with those of the 'common' chinotto, considering leaves, shoots, fruits and seed morphology and juice composition. In addition, the colour evolution of fruit flavedo was monitored by reflectance spectroscopy. Molecular analyses were performed using SSR, AFLP and RNA-seq-derived markers, providing tools to discriminate 'Chinotto di Savona' from C. myrtifolia. A cytogenetic analysis was performed to assess ploidy of the Chinotto accessions. Findings confirm the genetic similarity of 'Chinotto di Savona' and C. myrtifolia , supporting the running hypothesis of their origin from somatic mutations of sour orange. Further analysis will be needed in order to fully understand whether they are independent somatic mutations of sour orange or if they originated from each other. [ABSTRACT FROM AUTHOR]