Exploring the hormonal and molecular regulation of sand pear (Pyrus pyrifolia) seed dormancy

Although pear species (Pyrus spp.) are widely cultivated as an important fruit tree in the world, the regulatory mechanism of their seed dormancy is still unclear. In this research, the role of endocarp, seed coat and embryo in sand pear (Pyrus pyrifolia) seed dormancy was analysed by detecting the endogenous abscisic acid (ABA) and analysing germination experiments with different treatments. The results suggest that a combination of testa and embryo impose sand pear seed dormancy. The high concentration of endogenous ABA in the embryo effectively inhibited seed germination. The high concentration of ABA in the endocarp, as well as in the testa, suggests that dissipation and/or degradation of endogenous ABA in imbibed embryos were suppressed to maintain ABA-inhibited germination. The ABA and gibberellic acid (GA) key signalling genes, including ABI3-5, GAI, RGA and RGL2, were cloned and their expression was analysed in ABA-treated embryos and embryos of imbibed nutlets, imbibed true seeds (endocarp removed) and GA-treated true seeds. The results revealed regulation by ABA of the expression of ABA and GA signalling factors controlling the dormancy release of sand pear imbibed seeds.