Spatial and temporal changes of mineral nutrients and carbohydrates in cuttings of four stone fruit rootstocks and their contribution to rooting potential

Abstract

Hardwood cuttings of four stone fruit rootstocks (Cadaman, Rootpac-R, GF677 and Myrobalan 29C) were used as planting material to induce rooting in a bottom-heated cold frame. Cuttings were taken during four successive months from the basal, middle and apical part of the current seasons shoot. Carbohydrates and mineral nutrients were analyzed in the bases of the cuttings right before auxin application (before their placement in the frame), in order to assess any relation with the rooting capacity of the cuttings. Rootpac-R and Myrobalan 29C proved to be quite easy to root (reaching almost 90% rooted cuttings), followed by GF677 and lastly by Cadaman, which was the most recalcitrant rootstock to root by hardwood cuttings. Rootstocks were clearly distinguished by Principal Components Analysis and discriminant analysis, based on the measured parameters. Cuttings’ bases of the difficult to root Cadaman were characterized by high carbohydrate and nitrogen concentration, but relatively low ratio (carbohydrates versus nitrogen) while the opposite was found in the bases of the easy to root Rootpac-R. The latter was characterized along with Myrobalan 29C by high boron and manganese concentrations. It was clear that carbohydrate concentration does not have a major role in the rooting potential of the cuttings of the four rootstocks used in this study, while the ratio of carbohydrates versus nitrogen may have a more crucial role. Cuttings from the basal and middle part of the shoot rooted in higher percentages than those form the apical part, while November and December were in most cases the preferred months to take cuttings. Furthermore, a hypothesis is described based on the concentration of boron and manganese, on their possible role in regulating (directly or indirectly) the activity of IAA oxidase enzyme, at a time when high endogenous IAA is not desirable.