Dry Matter Partitioning and Carbohydrate Status of 'Kawanakajima Hakuto' Peach Trees Grafted onto Different Rootstocks or with an Interstock at Pre-bloom Period

Abstract

'Kawanakajima Hakuto' peach trees grafted onto Prunus tomentosa often show graft-incompatible symptoms. In relation to the tree decline, dry matter partitioning and carbohydrate status of various tree parts at pre-bloom period were investigated in 'Kawanakajima Hakuto' grafted on P. persica (PP), P. tomentosa (PT), and a compatible interstock/P. tomentosa (IS). Under non-bearing conditions of three-year-old trees, the total whole tree dry matter amount of PT was only half of PP, whereas IS was greater than PT. However, the ratio of scion to rootstock (S/R ratio) in dry matter levels was similar (0.57-0.59) in all combinations. The starch content, the major carbohydrate in various parts, was higher in the rootstock than in scion parts, that in the roots being highest in PP among the combinations. The total amount of non-structural carbohydrate (starch+simple sugars) per tree in IS and PT was half and one-third of PP, respectively. The greatest amount of non-structural carbohydrate was found in φ<2mm roots, regardless of combinations. The S/R ratio in non-structural carbohydrate levels was 0.18 for PP, 0.31 for IS, and 0.30 for PT. On bearing four-year-old trees, the S/R ratio in dry matter levels was reduced in PP (0.47) but increased in IS (0.63) and PT (0.66). The S/R ratio in non-structural carbohydrate levels was 0.16, 0.65, and 0.80 for PP, IS, and PT, respectively. These results suggest that the tree decline in PT is partially promoted by the depletion of non-structural carbohydrate reserve at the pre-bloom period. Furthermore, the use of compatible interstock improves dry matter and non-structural carbohydrate status especially in the rootstock.