Seasonal changes in starch and soluble sugar contents of two peach cultivars on Prunus tomentosa rootstock showing different degree of tree decline

Abstract

'Kawanakajima Hakuto' peach trees often show a greater incidence of tree decline than do 'Akatsuki' trees when grafted onto Prunus tomentosa rootstock. To seek the cause of the decline, seasonal changes in carbohydrate status of root, shoots, and leaves of the two cultivars grafted on P. tomentosa and P. persica were analyzed. There were no significant differences in the starch and soluble sugar contents between 'Akatsuki' and 'Kawanakajima Hakuto' grafted on either rootstock during the dormant period but at the pre-bloom period, the root starch content in both cultivars grafted on P. tomentosa was only half that of trees grafted on P. persica. The starch content in roots and shoots of 'Kawanakajima Hakuto' on P. tomentosa continued to be lower than that on P. persica during the growing period, Whereas it differed little on 'Akatsuki' on two rootstock, similar trends were found in total sugar and sorbitol contents of the roots. No conspicuous difference between the cultivars was found in other parameters, such as sugar contents of shoots and leaves, in relation to tree decline. Therefore, the cause of decline for 'Kawanakajima Hakuto' trees grafted on P. tomentosa is attributed partly to the depletion of starch and sorbitol in the roots and starch in the shoots during the growing season.