Abstract
For fruit tree (Prunus) species, flower bud dormancy completion determines the quality of bud break and the flowering time. In the present climate change and global warming context, the relationship between dormancy and flowering processes is a fundamental goal in molecular biology of these species. In almond [P. dulcis (Miller) Webb], flowering time is a trait of great interest in the development of new cultivars adapted to different climatic areas. Late flowering is related to a long dormancy period due to high chilling requirements of the cultivar. It is considered a quantitative and highly heritable character but a dominant gene (Late bloom, Lb) was also described. A major QTL (quantitative trait loci) in the linkage group (LG) 4 was associated with Lb, together with other three QTLs in LG1 and LG7. In addition, DAM (Dormancy-Associated MADS-Box) genes located in LG1 have been largely described as a gene family involved in bud dormancy in different Prunus species including peach [P. persica (L.) Batsch] and Japanese apricot (P. mume Sieb. et Zucc.). In this work, a DAM transcript was cloned and its expression was analysed by qPCR (quantitative Polymerase Chain Reaction) in almond flower buds during the dormancy release. For this purpose two almond cultivars (‘Desmayo Largueta’ and ‘Penta’) with different chilling requirements and flowering time were used, and the study was performed along two years. The complete coding sequence, designated PdDAM6 (Prunus dulcis DAM6), was subjected to a phylogenetic analysis with homologous sequences from other Prunus species. Finally, expression dynamics analysed by using qPCR showed a continuous decrease in transcript levels for both cultivars and years during the period analysed. Monitoring almond flower bud dormancy through DAM expression should be used to improve almond production in different climate conditions.
Highlights
During autumn temperate fruit trees (Prunus) activate a survival strategy called endodormancy, to protect against unfavourable chill conditions
Our results clearly indicated that the level of expression of DAM6 in both almond cultivars with study the biological role of Dormancy Associated MADS-Box (DAM) proteins during flower bud dormancy progression in almond
Our results clearly indicated that the level of expression of DAM6 in both almond cultivars with dormancy progression, for the late cultivar ‘Penta’, a relative increase was observed prior to different chilling requirements andsupported flowering time decreased concomitantly with chilletaccumulation dormancy release
Summary
During autumn temperate fruit trees (Prunus) activate a survival strategy called endodormancy, to protect against unfavourable chill conditions. Trees cease growth and form structures called buds in order to protect meristems from unfavourable environmental conditions, including low temperature and desiccation [1]. Chill accumulation allows the progression from flower bud endodorrmancy stage to flower bud ecodormancy which is regulated by heat accumulation [2]. Flowering time in almond [Prunus dulcis (Miller) Webb] is mainly dependent on chilling requirements to overcome this endodormancy stage [3]. These chilling requirements are considered a cultivar-dependent trait, correlated with species or cultivar origin [4,5].
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