Effect of the cutting size and morphological factors of pruned branches on improving the productivity of rooted cuttings in pinus thunbergii hedges

Abstract

We investigated the morphological and genetic factors affecting the rooting ability of cuttings and the shoot production of hedges of Pinus thunbergii by performing two different experiments. The effect of cutting size on rooting ability was investigated by using shoot cuttings obtained from five hedges (5̃6 years old). The shorter and thinner cuttings tended to show better rooting ability, and the rooting ability was different among individual hedges. In order to clarify the factors affecting the numbers and the sizes of the shoots obtained from the hedges, we measured several morphological traits of the shoots and the pruned branches in three 4-year-old hedges for each of the five half-sib families. A stepwise regression analysis suggested that the number of shoots per pruned branch was affected by the length of sprouting zone and the diameter of the pruned branch. The sizes of the shoots were most affected by the diameter of the pruned branch. Nested ANOVA showed that the number of shoots per pruned branch, the diameter of the pruned branch, and the length of the sprouting zone significantly varied among the families. These results suggested that family selection can improve the numbers of shoots in P. thunbergii hedges.