Fruit‐set on small Chardonnay and Shiraz vines grown under varying temperature regimes between budburst and flowering

Abstract

Small Chardonnay and Shiraz vines were grown under controlled conditions at 25°/20°C day/night temperatures but transferred for one week to 17°/14°C or 12°/9°C at four stages of growth between budburst and flowering. In Chardonnay, half the vines were given supplementary pollination with pollen produced under favourable conditions. Per cent fruit‐set and berry number per bunch of Chardonnay were reduced by about one third to one half by 12°/9°C, applied just before and at the early stage of flowering. At these stages, and with this low‐temperature treatment, supplementary pollination had significant positive effects. Total seed number per berry was not affected by treatment, but the proportion of hollow seeds increased in the treatments which suffered reduced set. This resulted in a positive relation between the number of functional seeds per berry and the number of berries per bunch. In Shiraz, the differences between the various treatment means were small and mostly not significant. It is concluded that the reduction in fruit‐set of Chardonnay due to cool temperatures near flowering is due to detrimental effects on both pollen and ovules. Copyright © 1995, Wiley Blackwell. All rights reserved