Unequal deployment of clones to seed orchards by considering genetic gain, relatedness and gene diversity

Related clones in seed orchards lead to inbreeding depression and reduced genetic value of the seeds. This study aims to develop the methodology for deployment of related clones to seed orchards when the breeding value and the pedigree are available for each candidate. The following goals were considered: high genetic gain, high genetic gain adjusted for predicted inbreeding depression (net gain), high gene diversity, and high effective clone number. The selection strategies included truncation selection with or without relatedness restrictions, maximizing genetic gain (linear deployment) with or without restrictions on relatedness and maximizing net gain. The selection strategies were applied to Norway spruce seed orchard candidates evaluated in clonal tests. The material comprised full-sib and half-sib relationships. Comparisons were made both at the same gene diversity and at the effective clone number. Maximizing net gain by unequal ramet number deployment resulted in considerable higher net gain and a considerable reduction of related ramets in many comparisons. Linear deployment restricted against related clones compared at the same status number resulted in almost as high net gain. Reduction in gene diversity may be a more important reason to avoid relatives in seed orchards than the subsequent inbreeding for achieving a high net gain.