Detection of Quantitative Trait Loci Controlling the Content of Phenolic Compounds in an Asian Plum (Prunus salicina L.) F1 Population

Abstract

Consumption of fresh fruit is known to protect against non-communicable diseases due to the fruit's content in compounds with an antioxidant capacity, among them is polyphenols. Asian plums (Prunus salicina L.) accumulate more than 40 phenolic compounds, with a remarkable diversity in their profiles, depending on the variety and environmental conditions. Although candidate genes have been indicated to control this trait, the loci controlling its phenotypic variation have not yet been defined in this species. The aim of this work was to identify the quantitative trait Loci (QTL) controlling the phenolic compounds content in the Asian plum skin and flesh. Using UHPLC-DAD-Orbitrap-MS, we determined that cyanidin-3-glucoside and cyanidin-3-rutinoside are the main anthocyanins in Asian plums. Other anthocyanins found to a lesser extent were tentatively identified as cyanidin bound to different sugar and procyanidin moieties. Then we phenotyped fruits of 92 and 80 F1 seedlings from the cross < “98.99” × “Angeleno”> (98 Ang) for two harvest seasons. We used HPLC-DAD to quantify single anthocyanin and spectrophotometric techniques to determine the total content of phenols, flavonoids, procyanidins, and antioxidant activity (DPPH and FRAP). To determine the phenotype-genotype association of phenolic compounds content, phenotypic values (adjusted by linear mixed-effects models), genotypic data and linkage maps were analyzed with the multiple QTL model (MQM) approach. We found a total of 21 significant trait-marker associations: 13 QTLs segregating from “98.99” and 8 QTLs from “Angeleno.” From these associations, 8 corresponded to phenolic compound content in the flesh and 13 in the skin. Phenotype variance was explained by the detected loci, ranging from 12.4 to 27.1%. The identified loci are related to the content of cyanidin-3-glucoside (LG4), cyanidin-3-rutinoside (LG4), total flavonoids and procyanidins (LG5 and LG8), and minor anthocyanin compounds (LG3 and LG4). These results will help improve the efficiency of breeding programs for the generation of Asian plum varieties with high phenolic compound content.

An Upgraded, Highly Saturated Linkage Map of Japanese Plum (Prunus salicina Lindl.), and Identification of a New Major Locus Controlling the Flavan-3-ol Composition in Fruits

“…Both the F1 progeny and the parents showed greater contents of flavan-3-ols in the skin than in the flesh in T1 and T2. Flavan-3-ol contents agree with the total amount of phenolic compounds of the Japanese plum fruits, which have higher accumulation in the skin than in the flesh (Cabrera-Bañegil et al, 2020;Valderrama-Soto et al, 2021). Also, we observed a greater accumulation of C and EC in T2 than T1.…”

“…As T2 samples were used as a comparison to verify the observed trends in T1, we decided not to sample these 15 seedlings. Samples employed in this study were the same as those from the studies reported by Salazar et al (2017Salazar et al ( , 2020 and Valderrama-Soto et al (2021). Fruits were harvested following the criteria reported by Contador et al (2016), with chlorophyll absorbance index (IAD) values between 1 and 1.40 units and a firmness close to 40 N. After harvest, the fruits were frozen using liquid nitrogen and stored at -20 • C until sample preparation.…”

“…The genotypic data employed in this study has been used for reconstructing the previously reported linkage maps, in which the genomes of Prunus persica v1.0 and v2.1 were employed as references (Salazar et al, 2017(Salazar et al, , 2020Valderrama-Soto et al, 2021). We updated previous linkage maps of '98-99' and ' Angeleno, ' using P. salicina 'Sanyueli' as reference genomes (Liu et al, 2020a) instead of peach.…”

“…Quantitative trait loci mapping is a tool that identifies loci controlling traits of interest (Collard et al, 2005). Through QTL analysis, the loci controlling the ripening time, skin color, fruit mass, polar diameter, shape, blooming date, fruit development period, soluble solids content, malic acid, texture, and content of phenolic compounds have been described in the Japanese plum (Salazar et al, 2017(Salazar et al, , 2020Valderrama-Soto et al, 2021). The studies mentioned above were performed by constructing linkage maps with GBS-based single-nucleotide polymorphisms (SNPs), called upon for mapping the obtained reads to peach v1.0 and v2.1 as reference genomes (Verde et al, 2013(Verde et al, , 2017, and describing the synteny among species from the same genus.…”

“…Therefore, in the current study, we associated genetic loci with the flavan-3-ol content of the mesocarp and exocarp of the Japanese plum fruits. Here, we reported a new version of the linkage maps of '98-99' and ' Angeleno' (Salazar et al, 2017(Salazar et al, , 2020Valderrama-Soto et al, 2021), now improved considering the release of a high-quality reference genome for Prunus salicina Lindl. (Liu et al, 2020a).…”