A repeatability study of trait assessment in a Pinus patula breeding programme

Abstract

A repeatability study of tree height, diameter at breast height (DBH), stem and crown form assessments was undertaken. Trees were measured four times by two independent teams. The repeatability of the five traits was estimated. The effect of repeatability on the heritability of the traits was determined. In order to obtain an indication of the feasibility of repeating measurements, the genetic gains were calculated for a hypothetical breeding population. The Best Linear Prediction (BLP) rankings of the four repetitions of the measurements were compared, with selection being based on volume, stem and crown. The repeatabilities for height (0,81), DBH (0,98) and volume (0,97) were high and the heritabilities of these traits showed only small increases with repeated measurements. Stem and crown form which were scored on a subjective scale, showed a repeatability of 0,61 and 0,62 respectively. Repeating scoring of these traits lead to bigger increases in the heritability with repeated measurements. Increases i...