Clonal selection in <i>Cupressus</i><i>sempervirens</i>: estimates of genetic parameters in juvenile growth

Abstract

Fifty common cypress (Cupressussempervirens L.) clones were evaluated at two sites in central Italy over a period of 5 years (1983–1987) for height growth, degree of resistance to Seiridiumcardinale, and diameter growth (1986 and 1987 only). Phenotypic correlations between height and diameter were high, positive, and significant. No correlation was found between degree of resistance and growth traits. Analysis of variance indicated that clone, site, and site–clone interaction were the significant sources of variation for each year and trait. The trend of height variance components over years indicated that after the 1st year (planting year) site–clone interaction and experimental error remained more or less constant, while clonal effect increased and site effect decreased over years. The evaluation of the expected genetic gains from selection indicated that the costs of a site-specific breeding program, on sites similar to the two tested in this paper, were not economically justified.