Ethephon-Mediated Bloom Delay in Peach Is Associated With Alterations in Reactive Oxygen Species, Antioxidants, and Carbohydrate Metabolism During Dormancy.

Md Tabibul Islam,Sherif M Sherif,Jianyang Liu

doi:10.3389/fpls.2021.765357

Md Tabibul Islam, Sherif M Sherif + Show 1 more

Open Access

https://doi.org/10.3389/fpls.2021.765357

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Abstract

Ethephon (ET) is an ethylene-based plant growth regulator (PGR) that has demonstrated greater efficacy in delaying bloom in deciduous fruit species. However, the underlying mechanisms by which ET modulates dormancy and flowering time remain obscure. This study aimed to delineate the ET-mediated modulations of reactive oxygen species (ROS), antioxidants, and carbohydrate metabolism in relation to chilling and heat requirements of “Redhaven” peach trees during dormancy. Peach trees were treated with ethephon (500ppm) in the fall (at 50% leaf fall), and floral buds were collected at regular intervals of chilling hours (CH) and growing degree hours (GDH). In the control trees, hydrogen peroxide (H2O2) levels peaked at the endodormancy release and declined thereafter; a pattern that has been ascertained in other deciduous fruit trees. However, H2O2 levels were higher and sustained for a more extended period than control in the ET-treated trees. ET also increased the activity of ROS generating (e.g., NADPH-oxidase; superoxide dismutase) and scavenging (e.g., catalase, CAT; glutathione peroxidase) enzymes during endodormancy. However, CAT activity dropped significantly just before the bud burst in the ET-treated trees. In addition, ET affected the accumulation profiles of starch and soluble sugars (hexose and sucrose); significantly reducing the sucrose and glucose levels and increasing starch levels during endodormancy. However, our study concluded that variations in ROS levels and antioxidation pathways, rather than carbohydrate metabolism, could explain the differences in bloom time between ET-treated and -untreated trees. The present study also revealed several important bud dormancy controlling factors that are subject to modulation by ethephon. These factors can serve as potential targets for developing PGRs to manipulate bloom dates in stone fruits to avoid the ever-increasing threat of spring frosts.

Highlights

Peach (Prunus persica) is a highly prized seasonal fruit worldwide
We showed that ethephon altered H2O2 accumulation during endodormancy, sustaining a high level of H2O2 for 200 chilling hours (CH) beyond the control’s peak
Ethephon application increased the activity of these enzymes and stimulated the enzymatic antioxidation pathways, such as those mediated by CAT and glutathione peroxidase (GPx), which is necessary for maintaining reactive oxygen species (ROS) at sub-lethal levels

Summary

Introduction

The production of peach in several fruit-growing regions in the United States and worldwide often suffers from damages caused by late-spring frosts. The risk of frost damage is projected to rise due to global climate change, and more variable, extreme weather events. Global warming has the potential to reduce winter chill, threatening the production of fruit and nut crops in several regions (Luedeling et al, 2011). Another remarkable effect of climate warming is the changes in plant phenology, which has caused many woody species to suffer increased frost damages in the US and Europe (Augspurger, 2013; Ma et al, 2018). There has been a need for a chemical treatment (s) that could delay budburst and bloom date of vulnerable cultivars and species beyond the last day of frost (Nzokou and Nikiema, 2008; Grijalva-Contreras et al, 2011; Liu and Sherif, 2019a; Liu et al, 2021)

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