Ethylene-Mediated Modulation of Bud Phenology, Cold Hardiness, and Hormone Biosynthesis in Peach (Prunus persica).

Jianyang Liu,Sangeeta Sapkota,Timothy S Artlip,Pratibha Ravindran,Prakash P Kumar,Md Tabibul Islam,Sherif M Sherif

doi:10.3390/plants10071266

Abstract

Spring frosts exacerbated by global climate change have become a constant threat to temperate fruit production. Delaying the bloom date by plant growth regulators (PGRs) has been proposed as a practical frost avoidance strategy. Ethephon is an ethylene-releasing PGR found to delay bloom in several fruit species, yet its use is often coupled with harmful effects, limiting its applicability in commercial tree fruit production. Little information is available regarding the mechanisms by which ethephon influences blooming and bud dormancy. This study investigated the effects of fall-applied ethephon on bud phenology, cold hardiness, and hormonal balance throughout the bud dormancy cycle in peach. Our findings concluded that ethephon could alter several significant aspects of peach bud physiology, including accelerated leaf fall, extended chilling accumulation period, increased heat requirements, improved cold hardiness, and delayed bloom date. Ethephon effects on these traits were primarily dependent on its concentration and application timing, with a high concentration (500 ppm) and an early application timing (10% leaf fall) being the most effective. Endogenous ethylene levels were induced significantly in the buds when ethephon was applied at 10% versus 90% leaf fall, indicating that leaves are essential for ethephon uptake. The hormonal analysis of buds at regular intervals of chilling hours (CH) and growing degree hours (GDH) also indicated that ethephon might exert its effects through an abscisic acid (ABA)-independent way in dormant buds. Instead, our data signifies the role of jasmonic acid (JA) in mediating budburst and bloom in peach, which also appears to be influenced by ethephon treatment. Overall, this research presents a new perspective in interpreting horticultural traits in the light of biochemical and molecular data and sheds light on the potential role of JA in bud dormancy, which deserves further attention in future studies that aim at mitigating spring frosts.

Highlights

Ethephon was applied at 50% leaf fall (LF) which corresponded to 40 chilling hour (CH)
Our results indicated that both ethephon concentration and application timing are important factors that contribute to the damaging impact of ethephon, as more damage to tree branches was observed with high concentrations and early stage of leaf fall (Figure 6B)
We demonstrated that fall application of ethephon impacted several aspects of peach floral bud phenology, including accelerated leaf fall, extended chilling accumulation period, increased heat requirements, improved cold hardiness, and delayed bloom date

Summary

Introduction

Temperate fruit production is often challenged by late spring frosts; the sporadic freezing temperatures that occur during spring after the weather begins to warm up. Spring frosts can damage or kill newly developed flowers and fruitlets, thereby substantially reducing fruit yield and quality. The concerns of spring frosts have been rising in recent years, especially in the context of climate change and its effects on the phenology of woody species and the frequency of freezing events during springtime [1,2,3]. Spring frosts impact a wide range of temperate perennials and threaten the production of several economically important fruit species such as stone fruits. The flowering time of stone fruits often coincides with the occurrence of spring frosts, making floral organs especially prone to frost injuries

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