Translocation and partitioning of 13C-photosynthates in the shoot with emphasis on berry coloration in 'Pione' grapes

Abstract

Scions from two mature 'Pione' vines, which bore well-colored berries (vines A and B, superior berry color, SBC) and two with poorly colored ones (vines C and D, inferior berry color, IBC) annually, were grafted on Teleki 5BB rootstocks. The vines of the two strains were then planted in the same vineyard. Shoot growth and berry development on each vine were recorded throughout the growing season. The partitioning of 13C-photosynthates from leaves into the various parts of the shoot of the two strains, which were exposed to 13CO2 at two weeks after veraison, was investigated. No significant differences in shoot elongation, increment of leaf area per shoot, and changes in chlorophyll content of leaves between the two strains were observed. No notable difference in berry enlargement between the two strains was observed, although the berries at harvest from vines.B and D were significantly heavier than those from vines A and C. The total soluble solids contents of the juice and anthocyanin levels of the skins were higher in berries from SBC vines than in those from IBC vines throughout the ripening stage; they increased significantly in the SBC vines two to three weeks after veraison. At harvest, anthocyanin content in the berry skins from vines of SBC was two to three times higher than in those from vines of IBC. At the end of 13CO2 feeding, the leaves on the main shoot of the SBC vines contained significantly more 13C label than those of the IBC vines. 13C concentration in leaves on both main and lateral shoots on all vines decreased rapidly for 24 hr after feeding followed by a gradual decrease, whereas it increased in berries with time. At 72 hr and 120 hr after feeding, 13C - photosynthates were translocated into berries larger in SBC vines than those in IBC vines. At 120 hr after feeding, the distribution ratio of 13C-photosynthates in the berries was higher in SBC vines than in IBC vines, while it was the reverse in the leaves on the main shoot. The relationship between translocation and partitioning of photosynthates and the accumulation of sugar and anthocyanin in berries, which differed between vines of the two strains, is discussed.