Abstract Measurements were made on Pinus resinosa Ait. at plantation ages of 9 or 11 years, on seedlings from 10 different provenances and on 72 different one-parent progenies. Each seed source was represented in test plantings on at least two different sites. Two schemes of sampling, random and tallest trees only, were used. Statistically significant differences between progenies were noted although the range of variation was relatively small. Within the limits of the seed sources and sites that were sampled, the tallest seed source in each test had a height advantage of about 10 per cent over the plantation average. Components of variance calculated for one-parent progenies indicated substantial family influence on total height of the tallest trees. Genotype-site interaction was prevalent in data from random samples, possibly due to intertree competition. It was concluded that genetic gains in growth rate are possible but selection must be based on progeny tests of very high precision.
Lester et al. (Wed,) studied this question.