A.M. Weibel, G.L. Reighard
Dwarfing mechanisms of rootstocks are not well understood. The main objective of this study was to gain a better understanding of this mechanism induced by size-controlling peach rootstocks, based on the tree water physiology. One-year-old and 4-year-old ‘Redhaven’ and ‘Redtop’ cultivars grafted on Cadaman® (vigorous), Lovell (control), Pumiselect® (semi-vigorous) and Krymsk® 1 (most dwarfing) were used. Trunk diameter, tree height, number of growing points, diurnal shoot growth, and tree fresh and dry weight were evaluated. Stomata conductance, transpiration rate, stem water potential and hydraulic resistance were also evaluated. In addition, xylem vessel diameter from scion and rootstocks was measured. There was a relationship between scion vegetative growth as affected by rootstock and tree water status, where trees on Cadaman® and Lovell, had the largest growth, followed by Pumiselect® and finally by Krymsk® 1. Stem water potential was related to the daily shoot growth where the more size-controlling rootstocks had the lowest values. On average, shoot growth of trees on Cadaman® and Lovell grew daily about 2 m, while Pumiselect® and Krymsk® 1 produced less than 0.4 m. Stomata resistance of trees on Pumiselect® averaged 1.92 s cm-1, 1.72 s cm-1 on Krymsk® 1 and 1.30 s cm-1 on Cadman®. Transpiration rate was ~40% higher in Cadaman® than on Pumiselect®. Xylem vessel diameters of Lovell rootstocks were two fold greater than those of Krymsk® 1 rootstocks. These results suggested that seasonal changes in dry matter production and partitioning found in two peach cultivars may be influenced, at least in part, by seasonal variations in stem water potential, stomatal conductance and transpiration rates. The results also suggested that in peach rootstocks the main hydraulic resistance might be located at the root such as the case of Krymsk® 1 or graft union interface as in Pumiselect® depending on genotype combinations.
Weibel, A.M. and Reighard, G.L. (2012). DWARFING PEACH ROOTSTOCKS GENERATE SCION WATER STRESS. Acta Hortic. 962, 633-639
DOI: 10.17660/ActaHortic.2012.962.86
Prunus, size-controlling, hydraulic, stomata, resistance, xylem

Acta Horticulturae