The effects of climate change on the taste and textural attributes of foods remain largely unknown, despite much public interest. On the basis of 30–40 years of records, we provide evidence that the taste and textural attributes of apples have changed as a result of recent global warming. Decreases in both acid concentration, fruit firmness and watercore development were observed regardless of the maturity index used for harvest date (e.g., calendar date, number of days after full bloom, peel colour and starch concentration), whereas in some cases the soluble-solids concentration increased; all such changes may have resulted from earlier blooming and higher temperatures during the maturation period. These results suggest that the qualities of apples in the market are undergoing long-term changes.

To grasp the actual influence of global warming on fruit tree production in Japan, a questionnaire was sent to prefectural institutes for fruit tree research. All 47 prefectures responded. All prefectures replied that global warming had affected on at least one tree species. The impact had extended to almost all tree species. The tree species were classified in to two types by responses of fruit development to climate changes. One group was the earlier development type and the other was the prolonged development type. The former were tree species in which both flowering and maturation periods had accelerated; these included Japanese pears, peaches and Japanese apricots. The latter were tree species in which the flowering period had accelerated, while maturation period had not accelerated; this type included apples, Japanese persimmons, grapes and satsuma mandarins. Fruit qualities of the prolonged development type had clearly changed, for example coloring faintly, enlarging, reduction of acid, softening and spoiling rapidly. Freezing injury on evergreen fruit trees and figs had decreased, while it had increased on other fruit tree species. Late frost damage showed both increase and decrease by region.

The regulatory mechanisms underlying bud breaking (scale leaf elongation) and flowering in the lateral flower buds of Japanese pear (Pyrus pyrifolia Nakai 'Kosui') are unknown. To more fully characterize these processes, we treated pear trees with different amounts of chilling initiated at different times. Chilling for ∼900 h at 6 °C always induced bud breaking (scale elongation in ≥70% lateral flower bud) when provided between October and February, whereas chilling provided earlier (between October and December) was less effective on flowering (floret growth and development) than later chilling and the flowering rate increased with longer chilling durations. During chilling, the expression of pear DAMs (PpMADS13-1, 13-2 and 13-3) in lateral flower buds decreased as chilling accumulated irrespective of the timing of chilling. In addition, pear TFL1 (PpTFL1-1a) in the lateral flower buds was expressed at higher levels when the time interval for chilling was earlier. On the other hand, during forcing at 15 °C after chilling, the expression pattern of all three PpMADS13 genes was similar among the treatments, and the expression levels seemed lower in the treatment where scale leaves of the lateral flower bud elongated faster, whereas pear FT (PpFT2a) was expressed at higher levels in the buds whose flower clusters elongated more vigorously during forcing. From these results, we infer that flowering time may be mediated via the balance of flowering-related genes FT and TFL1, whereas bud breaking may be regulated via the DAM genes in Japanese pear.

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