Varietal differences in the relationship between maturation characteristics, storage life and ethylene production in peach fruit

The time courses of fruit weight, ground color of skin (a* value), flesh firmness, sugar content, titratable acidity and amount of ethylene produced were measured during growth, maturation and senescence of four peach cultivars (Prunus persica Batsch) with different keeping qualities. Special emphasis was placed on the relationships and differences among individual indices of maturation and the characteristics of ethylene production. In the melting-type cultivars 'Akatsuki', 'Kushigatahakuto' and 'Nagasawahakuho', increase in fruit size, changes in ground color, rise in sugar content and reduction in titratable acidity gradually proceeded after full bloom. After a cultivar-dependent period, postharvest ethylene production and softening were clearly accelerated. On-tree ethylene production occurred later. However, there were large varietal differences in the relationship between ethylene production and changes in the indices of maturation. In 'Kushigatahakuto', ethylene production and softening proceeded fruit enlargement, completion of changes in ground color, and the rapid rise in sugar content. In contrast, in 'Nagasawahakuho', which showed a slow and late softening, ethylene production started after attaining full size, accumulating near maximum sugar level and loss of ground color. In the stony hard-type cultivar 'Yumyeong', ethylene production and postharvest softening did not occur; the on-tree flesh firmness decreased to about 4.0 kg. However, the trends in increase in fruit size, change in ground color, sugar accumulation and decreased in titratable acidity, were similar to those of the melting-type cultivars. From these results, we conclude that there are large varietal differences in the softening and maturation characteristics of peach fruit and that the genetics is determinant of these differences.