Optimizing the size of root cutting in <i>Melia volkensii</i> Gürke for improving clonal propagation and production of quality planting stock

Abstract

Melia volkensii is a tree species growing in semi-arid regions of East Africa, and is recognized as one of the most valuable forestry species in such regions of Kenya. The use of root cutting is an easy method for its clonal propagation, but the most appropriate conditions have not been systematically examined. In this study, the relationship between diameter of root cut edge or fresh weight and formation frequency of adventitious bud were assessed. In addition, roots were divided into two fragments, and formation frequency of adventitious bud was compared between cross-sections roots without root tip and roots with root tip. Both the diameter of the cut edge and fresh weight of roots forming adventitious buds were significantly higher than in those not forming them (unpaired t-test, p<0.01). Formation frequency of adventitious bud was 77.0% in roots satisfying the criteria of cut edges diameter >15 mm and fresh weight >20 g, but it decreased (37.2%) in roots that did not meet this criteria. Based on anatomical analysis, an effect of the developmental stage of root fragments on adventitious bud formation was suggested, and root size is thought to reflect the stage of root development. The formation frequency of adventitious buds was 72% even in cross-sectioned roots, and the proportion was not significantly different from that of normal root tip (p>0.05). Therefore, it is concluded that root cutting using cross-sectioned roots are also available for clonal propagation.

Keywords: Clonal forestry, anatomical analysis of root, availability of cross sectioned roots