BUSCADOR RECOLECTA

Cider regions conserve a broad diversity of traditional cultivars for which knowledge has hardly evolved. Key
aspects of their reproductive biology are barely known, hindering improvement in orchard management and
resulting in highly variable yields. In this study, we characterized key aspects of the reproductive biology of some
traditional apple cultivars from the Basque-style cider-producing area in northern Spain (Basque Country and
Navarre). We tested for pollen quality, self-compatibility, and cross-compatibility (S-genotyping). The pollen
quality was good except for Urtebete, Errezila, Reineta Encarnada, and triploid varieties. Self-pollination results
confirm the need for pollinators, as only Moko and Txalaka showed certain self-compatibility. Regarding Sgenotyping,
the population proved very singular, with an atypically high frequency of S26, a frequent allele
within crabapples, and the appearance of a novel unpublished allele (S60). The knowledge generated for this
variety pool will contribute to a better choice of suitable pollinators, preventing the use of popular crabapple
varieties that are demonstrated to be partly incompatible with them, and will lead to an increase in potential
yields in the region., This work was supported the Diputación Foral de Gipuzkoa, Departamento de obras hidráulicas y urbanismo (contract number 2019907195) “Determinación de las causas de la baja productividad de las plantaciones de manzano en Gipuzkoa / Gipuzkoako sagarrondo landaketen produktibitate baxuaren arrazoiak zehaztea” and the projects APPLECUT (PID2019-108081RR-C21) and APPLEDIV (PID2022-141847OR-C32) financed by the Ministry of Science and Innovation (Spain). Open access funding provided by Universidad Pública de Navarra

Sustainability in the fruit industry and protection of local cultivars are nowadays important tasks for consumers and authorities. Phenolic compounds are interesting to explore because they play an important role in fruit-related health benefits. The phenolic profile of the regional and commercial Spanish apple cultivars was performed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). For a deeper understanding of their anti-inflammatory and antioxidant potential, the 5-lipoxigenase inhibition and NO− scavenging were evaluated. Moreover, cellular viability was determined to perform MTT assay in HepG2 and HeLa cell lines to discard cytotoxicity. The results showed that procyanidin B2 (PB2), 3-caffeoylquinic acid, epicatechin and 4-hydroxy benzoic acid were the most abundant phenolic compounds. Autochthonous apple cultivars showed better 5-LOX/NO− inhibition and nontoxic effects in the tested cell lines with an interesting profile of phenolic compounds. Local autochthonous apples can be considered a better source of bioactive compounds than the commercial samples.

Enzymatic browning (EB) endangers the adaptation of apple fruit cultivars to new markets, affecting organoleptic properties and producing economic losses. Polyphenol oxidases and polyphenol compounds play a key role in EB development in apple. However, the regulation of apple response to EB remains to be uncovered. In this study, three apple cultivars with different EB phenotypes ranging from low to high browning in apple pulp were used to study transcriptomic changes over time after fresh cutting (0, 30 and 60 min). This study allowed the identification of 1448 differentially expressed genes (DEGs), revealing both shared and genotype-specific responses, particularly in the affected metabolic pathways associated with EB. At 60 min (T60 vsT0), 77 DEGs were shared by all genotypes, suggesting a conserved regulatory network. This network included genes encoding for protein families such as calcium-binding proteins, heat-shock proteins, redox-responsive transcription factors, WRKY family transcription factors, zinc finger family proteins and disease resistance proteins among others. A co-expressed gene cluster, identified through Weighed Gene Co-Expression Network Analysis (WGCNA), was found to correlate with EB and included 323 genes enriched in several biological terms according to Gene Ontology analysis. Moreover, a more detailed analysis of identified WGCNA gene cluster regulatory sequences allowed the detection of cis-regulatory elements belonging to CAMTA, WRKY and WUSCHEL transcription factor families. The identification of these sequences alongside with an abundant and diverse amount of overexpressed transcription factors from various families (WRKY, ERF, GRAS, GATA, etc.) point out to a highly regulated stress-response that is strictly connected to innate plant immunity. These findings provide valuable insights into the molecular mechanism involved in apple fresh-cut browning and offer new potential targets for EB regulation.