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16 Pág., Cycling Dof transcription factors (CDFs) have been involved in different aspects of plant growth and development. In Arabidopsis and tomato, one member of this family (CDF1) has recently been associated with the regulation of primary metabolism and abiotic stress responses, but their roles in crop production under open field conditions remain unknown., This study was supported by the Ministerio de Ciencia e Innovación (MCIN) and the Agencia Estatal de Investigación (AEI) / 10.13039/501100011033/ (grants RTA2015-00014-c02-00 to JM and SGN; PID2020-114165RR-C21 to JM), (BIO2017-82873-R to JVC) (PID2019-104685GB-100 to JP-R, EB-F and FJM), the Gobierno de Navarra (PC036-037 BIOMEF to EB-F and FJM) and the Vicerrectorado de Investigación de la Universitat Politècnica de València (PAID-11-21 to SGN), J.C is funded by the National Agency for Research and Development (ANID) Chile with Program FONDECYT Regular 1190812 and ANID-Millennium Science Initiative Program-ICN17_022" and The GEP Chinese pre-doctoral fellowship to LY. We also want to acknowledge the "Severo Ochoa Program for Centres of Excellence in R&D" (CEX2020-000999-S) supported by MCIN/AEI/10.13039/501100011033 for supporting the scientific services used in this study., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2020‐000999‐S)

Editorial on the Research Topic: Secondary metabolism and fruit quality., MTS-B’s work was supported by the CICYT project PID2020-113965RB-I00/AEI/10.13039/501100011033. CRF was supported by the National Research and Development Agency (ANID) – Millenium Science Initiative Program – NCN2021_010 and FONDECYT/Regular 1210941.

Japanese plum fruits are rich in phenolic compounds, such as anthocyanins and flavan-3-ols, whose contents vary significantly among cultivars. Catechin (C) and epicatechin (EC) are flavan-3-ol monomers described in the fruits of this species and are associated with bitterness, astringency, antioxidant capacity, and susceptibility to enzymatic mesocarp browning. In this study, we aimed to identify quantitative trait loci (QTL) associated with the content of flavan-3-ol in Japanese plum fruits. We evaluated the content of C and EC in the mesocarp and exocarp of samples from 79 and 64 seedlings of an F1 progeny () in the first and second seasons, respectively. We also constructed improved versions of linkage maps from ‘98–99’ and ‘Angeleno,’ presently called single-nucleotide polymorphisms (SNPs) after mapping the already available GBS reads to Prunus salicina Lindl. cv. ‘Sanyueli’ v2.0 reference genome. These data allowed for describing a cluster of QTLs in the cultivar, ‘Angeleno,’ associated with the flavan-3-ol composition of mesocarp and exocarp, which explain up to 100% of the C/EC ratio. Additionally, we developed a C/EC metabolic marker, which was mapped between the markers with the highest log of odds (LOD) scores detected by the QTL analysis. The C/EC locus was located in the LG1, at an interval spanning 0.70 cM at 108.30–108.90 cM. Our results suggest the presence of a novel major gene controlling the preferential synthesis of C or EC in the Japanese plum fruits. This study is a significant advance in understanding the regulation of synthesizing compounds associated with fruit quality, postharvest, and human health promotion., This study has been funded by the National Agency of Research and Development (ANID)/the Scholarship Program/BECAS DE DOCTORADO NACIONAL/2020 – 21200330; Fondecyt Regular No. 1191446; Fondecyt Iniciación No. 11150662; Fondecyt Regular No. 1200718; FONDEF Project IT17I0069 Sweet Pekeetah: “un modelo tecnológico- comercial para una nueva variedad chilena de fruta”. JS was supported by the Ministry of Science and Innovation of Spain through the Juan de la Cierva incorporation contract (IJC2018-036623-I)

The alternative oxidase pathway (AOP) is associated with excess energy dissipation in leaves of terrestrial plants. To address whether this association is less important in palustrine plants, we compared the role of AOP in balancing energy and carbon metabolism in palustrine and terrestrial environments by identifying metabolic relationships between primary carbon metabolites and AOP in each habitat. We measured oxygen isotope discrimination during respiration, gas exchange, and metabolite profiles in aerial leaves of ten fern and angiosperm species belonging to five families organized as pairs of palustrine and terrestrial species. We performed a partial least square model combined with variable importance for projection to reveal relationships between the electron partitioning to the AOP (τa) and metabolite levels. Terrestrial plants showed higher values of net photosynthesis (AN) and τa, together with stronger metabolic relationships between τa and sugars, important for water conservation. Palustrine plants showed relationships between τa and metabolites related to the shikimate pathway and the GABA shunt, to be important for heterophylly. Excess energy dissipation via AOX is less crucial in palustrine environments than on land. The basis of this difference resides in the contrasting photosynthetic performance observed in each environment, thus reinforcing the importance of AOP for photosynthesis., This work was mainly supported by Ministerio de Economía y Competitividad (MINECO, Spain) (project PGC2018-093824-B-C41) and the ERDF (FEDER). Others funding were provided by FONDECYT No. 1191118 from National Agency for Research and Development (ANID) and the Chilean Scholarship Program/Becas de doctorado nacional/2017–21180329, the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie grant agreement no. 753301, the ‘Ramon y Cajal’ contract RYC2019-027244-I/AEI/10.13039/501100011033 and the European Social Fund.

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., This work has been funded by the National Agency of Research and Development (ANID), Chile: Fondecyt start into Research No. 11150662, Fondecyt Regular No. 1191446, and FONDEF Project IT17I0069 Sweet Pekeetah: un modelo tecnológico-comercial para una nueva variedad chilena de fruta; BB and CS-A were supported by BECAS DE DOCTORADO NACIONAL/2020 No. 21200330 and 21191605, respectively. The work of JS was supported by the Ministry of Science and Innovation of Spain through Juan de la Cierva incorporation contract (IJC2018-036623-I)