EFFECT OF PREHARVEST FRUIT TEMPERATURE ON RIPENING, SUGARS, AND WATERCORE OCCURRENCE IN APPLES

The influence of controlling temperature during apple (Malus domestica Borkh.) maturation on sugars, fruit maturity, and watercore occurrenc e was investigated in watercore-susceptible 'Himekami' and 'Fuji' appl es. The incidence of watercore at 13/5 and 23/15C was greater than at 33/25(C or ambient temperatures in 'Himekami' apples in 1991 and was g reater at 18/10C than at other temperatures in 'Fuji' apples in 1990. In 1992, the extent of watercore increased as fruit temperature decrea sed from 28 to 14C and 23 to 9C in 'Himekami' and 'Fuji' apples, respe ctively. Watercore occurrence affected by fruit temperature was not re lated to fruit maturity, as judged by ethylene evolution. The effect o f fruit temperature on sorbitol was relatively small compared with tha t on other sugars, and no relationship was found between watercore dev elopment and sugars. These results suggest that fruit temperature affe cts watercore expression independently of fruit maturity or sorbitol m etabolism in the fruit in watercore-susceptible apple cultivars.