Early-height variation between full-sibling families of Sitka spruce growing in Ireland.

Abstract

Progeny trials are an essential form of genetic testing required in every tree breeding programme. In Ireland, Sitka spruce (Picea sitchensis (Bong.) Carr) progeny created by controlled pollinations between 41 phenotypically superior parent trees have been planted in different full-sibling trials to evaluate the genetic value of family and parent material. Establishing full-sibling field trials is an expensive and labour intensive process and regular assessment of the progeny is required to evaluate the success of such trials. This study presents the first detailed examination of the Irish Sitka spruce full-sibling field trials, comprising 69 families measured after six to seven growing seasons. From the 69 families used, 25 were significantly taller compared to unimproved control material. For the most successful trial, a mean height gain of 10% was achieved by the improved material. Regression showed that height increment over a year was partly dependent on initial height at the beginning of the year, indicating that early selection of material might be an option. Additionally, one poorly performing female parent which produced generally low yielding progeny was identified. This parent should be removed from the breeding population to avoid future wasted investment and thus to save costs within the programme.