Impact of previous and current year’s climatic conditions on the quality and yield of three wine grape varieties and vintage evaluation in Tokachi, Hokkaido, Japan

Abstract

The wine grapes of Tokachi wine are produced at Ikeda in eastern Hokkaido, where the daily minimum air temperature drops below - 20 ℃ during winter. In this study, we investigated the impact of the previous and current year ʼ s climate conditions (air temperature, precipitations, and sunshine hours) on the fruit quality (Brix, acidity), yield of grapes and Tokachi wine ʼ s vintage evaluation using three varieties ʻ Kiyomi ʼ , ʻ Kiyomai ʼ , and ʻ Yamasachi ʼ from 1995 to 2016. ʻ Kiyomi ʼ is a clonal selection of the French-derived ʻ Seibel 13053 ʼ , while ʻ Kiyomai ʼ and ʻ Yamasachi ʼ are cold hardy hybrids derived from crosses of ʻ Kiyomi ʼ and Vitis amurensis . The mean temperature from April to September and rainfall from August to September showed significant positive and negative correlations with the vintage evaluation in Ikeda, respectively, as well as in Bordeaux, France. Brix value of “ Kiyomi ” was positively correlated with sunshine hours in August and September of the growing year, while its acidity was negatively correlated with the average daily maximum temperature of June and average high temperature of September of the growing year. On the other hand, the Brix value and acidity of ʻ Kiyomai ʼ and ʻ Yamasachi ʼ were strongly influenced by the climatic conditions of the previous year as well as the growing year. Acidity of ʻ Kiyomai ʼ was negatively correlated with the average temperature in June and November of the previous year, while Brix value of ʻ Yamasachi ʼ was positively correlated with the sunshine hours in July of the previous year. In cold regions such as Ikeda, recent global warming has been considered to have a positive effect on agricultural production. However, this study shows that not all conditions associated with warming are positive for Ikeda ʼ s grapes and Tokachi wine.