Three Aspects of Seed Production Genetic diversity should be promoted since a large range in genetic variation is necessary to achieve improvement of tree quality. Without sufficient genetic variability it is difficult to make gains for traits of interest. Any attempt to improve trees from a narrow base will be unsuccessful. Inbreeding depression results from a high proportion of self-pollination in the breeding population. This must be avoided at all costs since inbreeding confers a lack of fitness or a lack of adaptation.
Hybridization is a cross between two varieties or species.
Vigor and fitness are associated with hybridization between superior individuals. For agricultural crops, hybridization is generally between different varieties of the same species. However, in forestry hybridization most often occurs at the species level as interspecific hybridization. Relatively few organizations are willing or able to make the long term commitment necessary to establish orchards for tree seed production. If the decision is made to establish a seed orchard, a long term plan is very important.