Effects of Fluridone Treatment on Seed Germination and Dormancy-associated Gene Expression in an Ornamental Peach (Prunus persica (L.) Batsch)

Fluridone, an inhibitor of carotenoid biosynthesis, is known to prevent abscisic acid (ABA) biosynthesis and to affect the germination and dormancy of seeds in several plant species. This study investigated the effects of fluridone on seed germination of the ornamental peach ‘Yaguchi’, and on the transcript levels of genes related to seed dormancy in this plant. Seeds were rinsed for 2 days under running tap water (RS), then soaked for 1 day in 100 μM fluridone (F), and kept at 5°C for 2 weeks (2W). The germination rate significantly increased from 0% to 9.5% in the RS+F treatment and to 71.4% in the RS+F+2W treatment, while no germination occurred in the RS and RS+2W treatments. Seedlings in RS+F and RS+F+2W treatments formed dwarf shoots, i.e. about 10 cm, and morphological lesions on the leaves. The ABA content in embryonic axes decreased after RS and increased with RS+2W. It was decreased by the RS+F+2W treatment. RS+F+2W downregulated ABA-hy3, which encodes enzymes with key roles in ABA catabolism, while its effects on 9-cis-epoxycarotenoid dioxygenase (NCED1) in relation to ABA synthesis fluctuated. In contrast, Empfindlicherim Dunkelroten Licht 1 (EID1) was upregulated after fluridone treatment, suggesting that fluridone may activate positive ABA signaling pathways. Expression of GA2-oxidase8 (GA2-ox8) was not affected by fluridone. MADS-box protein JOINTLESS (LeMADS) and Late embryogenesis abundant protein D-34 (LEA D-34) were downregulated in the RS+F+2W treatment, suggesting that the expression of these genes are controlled by low temperature and the ABA inhibitor, and are involved in seed dormancy. These results suggest that ABA inhibitor treatments can be an alternative method to promote germination by controlling ABA content and its metabolism, and consequently changing expression of certain ABA- and dormancy-related genes including ABA-hy3, EID1, LeMADS, and LEA D-34, even under insufficient chilling conditions.