According to the intergovernmental panel on global change (IPCC), global air-temperature has risen by more than 0.7°C over the last 100 years, with East Asia, particularly Japan exhibiting an increase of nearly 1°C. A recent survey revealed that this temperature increase has already adversely affected crop growth in various respects, and are particularly noticeable in horticultural crops such as fruit trees, vegetables, and flowers. The phenological changes of horticultural crops caused by increased temperature can be frequently observed in fruit-size enlargement, softening of fruit flesh, increased acidity, skin/leaf burning, insufficient color development and fruit deformity, decreased fruit setting, lack of head formation in heading crucifers, increased physiological disorders such as tip-burn and blossom end-rot, delay of endodormancy, etc.
Meanwhile, optimum areas for horticultural crop cultivation are expected to shift northwards as the climatic change proceeds. This is also true with the onset and spread of insect pests. Diaphorinacitri (psylla), the citrus greening disease (Huanglongbing or HLB) vector, was first identified in Iriomote island (next to Taiwan), and has successively moved northwards to Yakushima island (close to Kyushu mainland) in 2002 with the increasing temperature.
An air-temperature increase of less than 1°C brought about serious phenological disorder in horticultural crops, thus resulting in substantial yield loss and devaluation of their market prices. IPCC projected that average air-temperature will rise at a maximum of 4°C during the 21st century. Hence, it has become urgent to develop effective and promising technologies to mitigate the serious risks brought about by climate change to horticultural crop production.