Peach fruit suture softening regulated by the interaction of nitrogen with cytokinin and ethylene

We investigated the factors that regulate ventral suture early softening of peach fruit. Experiments were carried out with fruits of peach Prunus persica (L.) Batsch cv. ‘Okubo’ under two levels of N application. We found that percentage of disordered fruit was much higher with high level of N application than with low N treatment, and the suture region of disordered fruit grew faster than that of normal fruit during the pit hardening phase, and a high level of endogenous zeatin was found in the suture region of disordered fruit. We also found that, compared to normal fruit, early softening fruit exhibited thicker and more developed vascular bundles in the suture region with a relatively larger area of phloem and xylem and more rapid development of the glandular cavity. Finally, ethylene release began earlier and reached its peak at the end of the pit hardening phase in disordered fruit. After treatment with 1-MCP, the ethylene peak disappeared and the number of disordered fruits were markedly reduced. These results indicate that the occurrence of peach fruit suture softening is affected by the interaction of nitrogen with cytokinin and ethylene.