Relationships between the Yearly Variation in the Developmental Phase and Fruit Qualities of Japanese Pear 'Kosui' and Climatic Factors

Abstract

Relationships were analysed between the yearly variation in the developmental phase and fruit quality of the Japanese pear ( Pyrus pyrifolia) cv. Kosui and climatic factors in Mie Prefecture, Japan, from 1987 and 2004. The annual mean air temperature tended to rise at an annual rate of 0.07 degrees C. This uptrend in the mean temperatures was especially remarkable from September to February. Along with the rise in the temperature, the estimated date of breaking of bud endodormancy in Kosui tended to be delayed at a rate of 0.49 day per year, possibly due to the rising temperatures during late autumn and winter. The flowering dates were negatively correlated with mean air temperatures at 10-day intervals from early February to mid-April and some of these mean air temperatures increased with advancing years. As a result, the flowering dates became earlier each year at a rate of 0.37 day per year. The date of peak harvest was positively correlated with the annual and became earlier each year at a rate of 0.32 day per year. The number of days from flowering to peak harvest was not correlated with the year. The developmental phase of Kosui in Mie Prefecture is being influenced by global warming. However, the sugar concentration in the fruits was influenced by mean air temperature and mean solar radiation from mid-July to mid-August and mean precipitation from late July to early August, although the yearly variations in sugar concentration in the fruit did not parallel the variations in annual mean air temperature.