For perennial plants, bud dormancy is a crucial step as its progression over winter determines the quality of bud break, flowering, and fruiting. In the past decades, many studies, based on metabolic, physiological, subcellular, genetic, and genomic analyses, have unraveled mechanisms underlying bud dormancy progression. Overall, all the pathways identified are interconnected in a very complex manner. Here, we review early and recent findings on the dormancy processes in buds of temperate fruit trees species including hormonal signaling, the role of plasma membrane, carbohydrate metabolism, mitochondrial respiration and oxidative stress, with an effort to link them together and emphasize the central role of reactive oxygen species accumulation in the control of dormancy progression.

BackgroundDepiction of the genetic diversity, linkage disequilibrium (LD) and population structure is essential for the efficient organization and exploitation of genetic resources. The objectives of this study were to (i) to evaluate the genetic diversity and to detect the patterns of LD, (ii) to estimate the levels of population structure and (iii) to identify a ‘core collection’ suitable for association genetic studies in sweet cherry.ResultsA total of 210 genotypes including modern cultivars and landraces from 16 countries were genotyped using the RosBREED cherry 6 K SNP array v1. Two groups, mainly bred cultivars and landraces, respectively, were first detected using STRUCTURE software and confirmed by Principal Coordinate Analysis (PCoA). Further analyses identified nine subgroups using STRUCTURE and Discriminant Analysis of Principal Components (DAPC). Several sub-groups correspond to different eco-geographic regions of landraces distribution. Linkage disequilibrium was evaluated showing lower values than in peach, the reference Prunus species. A ‘core collection’ containing 156 accessions was selected using the maximum length sub tree method.ConclusionThe present study constitutes the first population genetics analysis in cultivated sweet cherry using a medium-density SNP (single nucleotide polymorphism) marker array. We provided estimations of linkage disequilibrium, genetic structure and the definition of a first INRA’s Sweet Cherry core collection useful for breeding programs, germplasm management and association genetics studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0712-9) contains supplementary material, which is available to authorized users.

In temperate trees, optimal timing and quality of flowering directly depend on adequate winter dormancy progression, regulated by a combination of chilling and warm temperatures. Physiological, genetic and functional genomic studies have shown that hormones play a key role in bud dormancy establishment, maintenance and release. We combined physiological and transcriptional analyses, quantification of abscisic acid (ABA) and gibberellins (GAs), and modeling to further investigate how these signaling pathways are associated with dormancy progression in the flower buds of two sweet cherry cultivars. Our results demonstrated that GA-associated pathways have distinct functions and may be differentially related with dormancy. In addition, ABA levels rise at the onset of dormancy, associated with enhanced expression of ABA biosynthesis PavNCED genes, and decreased prior to dormancy release. Following the observations that ABA levels are correlated with dormancy depth, we identified PavUG71B6, a sweet cherry UDP-GLYCOSYLTRANSFERASE gene that up-regulates active catabolism of ABA to ABA glucosyl ester (ABA-GE) and may be associated with low ABA content in the early cultivar. Subsequently, we modeled ABA content and dormancy behavior in three cultivars based on the expression of a small set of genes regulating ABA levels. These results strongly suggest the central role of ABA pathway in the control of dormancy progression and open up new perspectives for the development of molecular-based phenological modeling.

18In temperate trees, optimal timing and quality of flowering directly depend on adequate winter dormancy 19 progression, regulated by a combination of chilling and warm temperatures. Physiological, genetic and 20 functional genomic studies have shown that hormones play a key role in bud dormancy establishment, 21 maintenance and release. We combined physiological, transcriptional analyses, quantification of 22 abscisic acid (ABA) and gibberellins (GAs), and modelling to further elucidate how these signaling 23 pathways control dormancy progression in the flower buds of two sweet cherry cultivars. 24Our results demonstrated that GA-associated pathways have distinct functions and may differentially 25 regulate dormancy. In addition, ABA levels rise at the onset of dormancy, associated with enhanced 26 expression of ABA biosynthesis PavNCED genes, and decreased prior to dormancy release. Following 27 the observations that ABA levels are strongly linked with dormancy depth, we identified PavUG71B6, 28 a sweet cherry UDP-GLYCOSYLTRANSFERASE gene that up-regulates active catabolism of ABA to 29 ABA-GE in the early cultivar. Subsequently, we successfully modelled ABA content and dormancy 30 behavior in three cultivars based on the expression of a small set of genes regulating ABA levels. These 31 results underscore the central role of ABA and GA pathways in the control of dormancy progression 32 and open up new perspectives for the development of molecular-based phenological modelling. 33

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