Flower and fruit thinning in relation to some fruit traits as affected by bloom time and within-tree position in peach

In Japanese peach culture, unnecessary flowers (buds) such that attach uprightly or toward centre of tree on the bearing shoots are removed simply and lightly by flower thinning and their fruiting levels are adjusted by fruit thinning done at two steps to control number of fruit remaining on the tree. However, fruit quality still varies widely within a tree and flesh disorders such as "reddish pulp" and "water-soaked brown flesh" occur in many of harvested fruit in recent years. We investigated the relationship between fruiting positions or flowering time and the variation in weight, soluble solids content (SSC) and occurrence of flesh disorders of fruit within a peach cv. white flesh type 'Benishimizu' tree. Fruit weight and SSC were significantly inferior in not only the fruit located on the bottom part of the main stem but also for the fruit borne from early blooming flowers and the rate of fruit showing severe "reddish pulp" disorder was also higher in these fruit. The fruit borne from early blooming flowers had lower sugar accumulation in the flesh than those from late blooming flowers during the latter half of Stage 3 of fruit growth. At present, we are trying to improve flower thinning so as to remove the flowers opening before full bloom. On fruiting shoots of white flesh type 'Shimizu Hakuto' peach that received thinning of early blooming flowers, the distribution rates of fruit that had weights less than 280 g were lower than those of fruiting shoots (= control) that received the standard fruit thinning. Occurrence rate of severe "reddish pulp" disorder when using this flower thinning protocol were significantly lower than the control. Based on the above results, flower and fruit thinning can improve fruit quality by considering not only the within-tree position of fruit but also the flowering time.