Physiology and promotion of seed germination in ornamental peach

The establishment of efficient seed treatments for early germination and seedling growth is required to shorten the time that seedlings are in the nursery and to shorten breeding cycles. In our previous studies, the following has been revealed: 1) a 7-day period of rinsing in water combined with chilling at 5°C for four weeks promoted the germination rate in seeds of 'Yaguchi' peach more than where two days of rinsing were combined with four weeks of chilling; 2) the abscisic acid (ABA)-related genes (NCED1, ABA 8-hydroxylase, and PP2C) and stress response genes (EID1, DREB2CA, and LEA D-34) were involved in seed germination; and 3) the treatment of fluridone, an inhibitor of ABA biosynthesis, could promote germination of seeds chilled at 5°C for two weeks, however, the seedlings showed dwarfism and had lesions on the leaves. In the study reported here, seeds were treated with procaine hydrochloride, an inhibitor of DNA methylation, and later with fluridone to investigate the involvement of DNA methylation in seed germination under conditions with insufficient chilling. The procaine treatments that were used did not alleviate dwarfism or lesion development but significantly increased the SPAD value of the leaves on the seedlings. Preventing leaf yellowing by procaine is beneficial in the case of forced germination using fluridone, although the mechanisms of interaction between procaine and fluridone are unknown. Further study will be necessary to identify the involvement of epigenetics in both the dwarfing process and in lesion development in the seedlings grown from the seeds that are exposed to insufficient chilling.