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The present study investigates the genetic determinism of flowering and maturity dates, two traits highly affected by global climate change. Flowering and maturity dates were evaluated on five progenies from three Prunus species, peach, apricot and sweet cherry, during 3-8 years. Quantitative trait locus (QTL) detection was performed separately for each year and also by integrating data from all years together. High heritability estimates were obtained for flowering and maturity dates. Several QTLs for flowering and maturity dates were highly stable, detected each year of evaluation, suggesting that they were not affected by climatic variations. For flowering date, major QTLs were detected on linkage groups (LG) 4 for apricot and sweet cherry and on LG6 for peach. QTLs were identified on LG2, LG3, LG4 and LG7 for the three species. For maturity date, a major QTL was detected on LG4 in the three species. Using the peach genome sequence data, candidate genes underlying the major QTLs on LG4 and LG6 were investigated and key genes were identified. Our results provide a basis for the identification of genes involved in flowering and maturity dates that could be used to develop cultivar ideotypes adapted to future climatic conditions. Heredity (2012) 109, 280-292; doi:10.1038/hdy.2012.38; published online 25 July 2012Keywords: Prunus; phenology; flowering date; maturity date; QTL analyses; candidate gene INTRODUCTIONIn the context of global climate change, flowering phenology of deciduous tree species is crucial as it may affect their productivity. In fruit tree orchards, flowering phenology has an indirect influence on spring frost damage, pollination, dormancy and maturity. Even though in a warming scenario, the current risk of frost damage might remain a preoccupation for growers subsequently to advanced flowering time and more irregularities of temperature conditions. Moreover, new risks are emerging as disruptions in floral phenology synchronization, which may disturb pollination for varieties that necessitate cross pollination. In addition, marked changes in the order of flowering time within a varietal range or between adjacent cropping areas may modify the orders of fruit maturity time and consequently disturb commercial specificities.The Prunus genus, within the Rosaceae family, is characterized by species that produce drupes as fruit, and can be divided into three major subgenera: Amygdalus (peach (Prunus persica (L.) Batsch) and almond (Prunus dulcis Mill.)), Prunophora (apricot (Prunus armeniaca L.)), Cerasus (sweet cherry (Prunus avium L.) and sour cherry (Prunus cerasus L.)). All these species are grown in climates with well-differentiated seasons where they have adapted to survive to low winter temperatures and summer drought. In Prunus, as in most woody perennials, the physiology and biochemistry of the flowering

Thirty-seven apricot varieties, including four new releases (Rojo Pasión, Murciana, Selene, and Dorada) obtained from different crosses between apricot varieties and three traditional Spanish cultivars (Currot, Mauricio, and Búlida), were separated according to flesh color into four groups. The L*, a*, b*, hue angle, and chroma color measurements on the skin and flesh as well as other quality indices including flesh firmness, soluble solids, titratable acidity, and pH were plotted against the total carotenoid content measured by HPLC. Among the 37 apricot varieties, the total carotenoid content ranged from 1,512 to 16,500 microg 100 g(-1) of edible portion, with beta-carotene as the main pigment followed by beta-cryptoxanthin and gamma-carotene. The wide range of variability in the provitamin A content in the apricot varieties encouraged these studies in order to select the breeding types with enhanced carotenoid levels as the varieties with a higher potential health benefit. The carotenoid content was correlated with the color measurements, and the hue angle in both flesh and peel was the parameter with the best correlation (R = 0.92 and 0.84, respectively). An estimation of the carotenoid content in apricots could be achieved by using a portable colorimeter, as a simple and easy method for field usage applications.

Fruit quality attributes were studied for two consecutive years in forty-three apricot cultivars and selections grown in a Mediterranean climate. Physical parameters (weight, size, flesh and skin colour, percentage of blush, firmness and percentage of dry matter), chemical parameters (total soluble solids content and acidity) and sensory parameters (attractiveness, taste, aroma and texture) were evaluated. A high variability was found in the set of the evaluated apricot genotypes and significant differences were found among them in all studied quality attributes. Year-by-year variations were observed for some pomological traits such as harvest date, flesh colour, fruit weight, firmness and soluble solids content. A high correlation was found among some apricot quality attributes. In addition, principal component analysis (PCA) made it possible to establish similar groups of genotypes depending on their quality characteristics as well as to study relationships among pomological traits in the set of apricot genotypes evaluated.