Effects of timing and intensity of elevated temperatures on reproductive development of field-grown Shiraz grapevines

Vinay Pagay,Cassandra Collins

doi:10.20870/oeno-one.2017.51.4.1066

Abstract

Aim: To investigate whether timing and duration of exposure to elevated temperatures impact the reproductive development of field-grown Shiraz grapevines.Methods and results: The reproductive responses of Shiraz grapevines (Vitis vinifera L.) to two levels of elevated temperatures at budburst and flowering were investigated in an irrigated vineyard in the Barossa Valley (South Australia) over two consecutive growing seasons. Custom-built under-vine ‘tents’ and closed flow-through chambers enclosing a set of grapevines in the field were used to raise canopy temperatures above ambient. Higher temperatures at flowering resulted in lower yields due to decreased fruit set in 2007-08, while yield was virtually unaltered the following year despite the lower fruit set. Two indicators of grapevine reproductive performance, Coulure Index and Millerandage Index that quantify abscised and underdeveloped berries, respectively, were calculated to be higher as a result of the heat treatments in both seasons. Stigma receptivity, pollen germination, and pollen tube kinetics were generally lower in vines grown under the tents.Conclusion: Flowering and fruit set are strongly influenced by temperature changes during this period of development.Significance and impact of study: This is one of the first field based studies to demonstrate that extreme temperatures (>35°C) during the flowering period detrimentally effect fruit set and final yield and thus providing critical knowledge for managing vineyards in a changing climate.

Highlights

Temperature is a primary environmental factor that plays a key role in affecting several plant physiological processes including phenology, vegetative growth, flowering and fruit set, crop development, yield and quality
Coulure Index (CI) values were consistently higher in the Under-vine ‘tents’ (UVT) vines compared to control vines, indicating that more flowers abscised under elevated temperatures
Given the similar Millerandage Index (MI) values of the two treatment groups, there did not appear to be a different proportion of berries on each cluster that were either seedless or live green ovaries (LGOs)

Summary

Introduction

Temperature is a primary environmental factor that plays a key role in affecting several plant physiological processes including phenology, vegetative growth, flowering and fruit set, crop development, yield and quality. While an increase in the average growing season temperature is likely to have negative effects on crop yield and quality, short episodes of extreme temperatures are expected to be even more detrimental at key phenological stages of plant development such as flowering and fruit set (Ferris et al, 1998; Hedhly et al, 2005; Prasad et al, 1999). Higher temperatures applied after budburst (until fruit set) advanced the phenology of berry set and had a negative effect on flower number per inflorescence (Buttrose and Hale, 1973). In Pinot Noir, there was a 23% decrease in fruit set and 21% decrease in ovule fertility when the maximum day-time temperature was 35°C compared to a maximum day-time temperature of 25°C (night temperatures were held constant at 20°C; (Kliewer, 1977)). Keller et al (2010) reported a 6% increase in fruit set when the ambient temperature at budburst of 10°C was increased to 15°C, whereas a similar temperature increase from 14°C to 19°C resulted in a 12% increase in fruit set

Objectives

Methods

Results

Discussion

Conclusion