Contrasting bloom dates in two apple cultivars linked to differential levels of phytohormones and heat requirements during ecodormancy

Apple production in temperate regions is continuously imperiled by spring frosts. Economic losses caused frost damage can be enormous, and the risk of such projected to rise due global climate change. Induction bloom delay has been suggested as a potential avoidance strategy. However, applicable practices toward this goal are largely lacking, primarily complexity mechanisms governing dormancy blooming deciduous woody perennials like pome fruits. Cultivars differing time provide suitable platform for investigating regulatory these phenological processes. In study, we investigated hormonal regulation bud two apple cultivars, ‘Honeycrisp’ ‘Cripps Pink’, which represent late- early-blooming respectively. Our results indicated that cultivars showed similar chilling requirements but differed significantly number growing degree hours (GDH) required burst flowering. Abscisic acid (ABA) levels were remarkably elevated dormant buds both during endodormancy, they higher buds, especially transition from endo- eco-dormancy. Through ABA biosynthetic catabolic genes, identified NCED1 NCED2, one gene CYP707A 2.3, whose differential transcript explain distinctive patterns cultivars. data also cytokinin (CK) Pink’ compared ‘Honeycrisp’, shortly before budburst. The study indicate differences times among explained, at least partially, heat Future investigations, omics would better understanding molecular networks linking hemostasis with apple.