The Effect of Low Temperature on Physiological, Biochemical and Flowering Functions of Olive Tree in Relation to Genotype

Niki Mougiou,Nektarios Kavroulakis,Georgios C Koubouris,Boushra Baalbaki,Stylianos Poulios,Konstantinos E Vlachonasios,Georgios Doupis

doi:10.3390/su122310065

Niki Mougiou, Nektarios Kavroulakis + Show 5 more

Open Access

https://doi.org/10.3390/su122310065

Copy DOI

Abstract

Olive tree growth and reproduction are severely affected by temperature extremes, compromising fruit yield. In that aspect, the olive varieties “Koroneiki” and “Mastoidis” were employed in a mild cold stress experiment, imitating night frost incidents to assess their biochemical, physiological and reproductive functions in relation to genotype. The physiological performance of the stressed plants was not significantly altered, suggesting that both cultivars were well adapted to mild cold night stress. The biochemical response of the plants, regarding antioxidant enzymes, H2O2 and TBARS accumulation, confirmed that both cultivars could cope with the stress applied. The mRNA levels of the PPO gene, which participates in hydroxytyrosol biosynthesis and plant defense, were elevated after 24-h stress at 0 °C, in both cultivars with “Mastoidis” plants exhibiting higher levels for a longer period. Three more genes involved in hydroxytyrosol biosynthesis upregulated their expression levels as a response to cold stress. The numerous plant phenology aspects measured reinforced the conclusion that both cultivars responded to the stress applied. The results of the present study may contribute to better understanding olive tree adaptive responses to low temperature events, an abiotic stress condition that is often present in an open plantation, thus assisting farmers on breeding and cultivar selection.

Highlights

The olive tree is a crop of high economic significance, and a cornerstone of a healthy diet due to the high nutritional value of its products, namely table olives and olive oil
Yield and olive oil quality are favored in areas with moderately cold winters as well as warm and dry weather during fruit maturation, olive cultivation is located mainly in the Mediterranean-type climate regions
“Mastoidis” 4-day stressed plants responded as the control plants, while the 2-day stressed plants had a non-significant increased Gs value the third day, as observed for photosynthetic rate (Pn)

Summary

Introduction

The olive tree is a crop of high economic significance, and a cornerstone of a healthy diet due to the high nutritional value of its products, namely table olives and olive oil. Olive cultivation and spread are geographically limited by temperature, an important climatic factor [1]. Yield and olive oil quality are favored in areas with moderately cold winters as well as warm and dry weather during fruit maturation, olive cultivation is located mainly in the Mediterranean-type climate regions. The exposure to drought and low temperatures is a major limiting factor for growing olives. Olive trees cannot tolerate temperatures less than −7 ◦C, but demand certain exposure to low temperature, at the range of 5–15 ◦C, during winter to overcome dormancy and be able to develop flowers in the subsequent spring [3]. Low temperature incidents during flowering may be responsible for an increase in shotberry incidence, which are abnormally grown small fruit commonly resulting from parthenocarpy [5]

Methods

Results

Conclusion