Rooting and vegetative growth of hardwood cuttings of 12 pomegranate (Punica granatum L.) cultivars

Abstract

Commercial pomegranate production area has increased substantially in the western hemisphere due to increased consumer interest in the fruit. Low nursery inventory has caused many growers to propagate vegetatively their own trees and the availability of only a few cultivars is believed to have played a role in a lack of diversity in the developing market. ‘Wonderful,’ the industry standard for pomegranate in several countries, has been propagated in the United States for over 100 years, yet there is limited scientific information regarding how to most effectively propagate ‘Wonderful’ and other important cultivars. This research included two experiments. Experiment 1 evaluated rooting percentages and vegetative growth attributes of hardwood cuttings of twelve cultivars (‘Ambrosia,’ ‘Desertnyi,’ ‘Eversweet,’ ‘Golden Globe,’ ‘Green Globe,’ ‘Haku Botan,’ ‘Ki Zakuro,’ ‘Loffani,’ ‘Nochi Shibori,’ ‘Parfianka,’ ‘Phoenicia,’ and ‘Wonderful’) utilizing a basal dip in a gel formulation of 3 g·L−1 indole-3-butyric acid (IBA). Experiment 2 evaluated auxin treatments which consisted of basal dip in water only (control) or a gel formulation of IBA (1.5gL−1 or 3gL−1) for hardwood cuttings of ‘Wonderful’ and two cultivars that rooted poorly in Experiment 1: ‘Ambrosia’ and ‘Green Globe.’ Measured response attributes included rooting success percentages, dry root mass, leaf area, plant height, number of shoots, apical shoot growth, total shoot length, branching, stem diameter, and relative chlorophyll content (SPAD value). ‘Wonderful’ and nine other cultivars rooted over 84% of the time using cuttings treated with 3gL−1 IBA. Differences in plant height and branching could be detected early in production. The effect of IBA concentration on rooting percentage and growth attributes varied among cultivars. Cuttings of ‘Ambrosia’ rooted best with 3gL−1 IBA versus 0 and 1.5gL−1 IBA, whereas rooting of cuttings of ‘Green Globe’ was similar among IBA rates. Plants of ‘Wonderful’ had significantly greater leaf area compared to those of ‘Ambrosia’ and ‘Green Globe.’ Stem diameter had no effect on rooting on any cultivar in either experiment. There were significant differences among cultivars in terms of chlorophyll content, with ‘Haku Botan’ and ‘Loffani’ having greener leaves than ‘Eversweet,’ ‘Ambrosia,’ and ‘Desertnyi.’