Aspekte nachhaltiger Züchtung

Abstract

Breeding has to compare response functions to be able to analyse the genetic control of trait expressions comprehensively and unconditionally to a specific modell. Such an approach calls for suitable methods to describe differences between response functions.The thesis is divided into two parts. In the first part of the thesis the characteristics of the measure of difference Delta for the description of quantitative and qualitative traits are analysed. The characteristics of Delta are compared with the genetic distance d_0 an derived measure for differences of distributions of quantitative traits. Delta describes the differences between collectives not on the basis of single position or dispersion parameters but it takes the complete variation of the trait into account. Delta allows to consider differences in trait expression gradually. Delta describes the difference between two distributions of quantitative and qualitative traits equally and independently of any modell. Comparing two collectives with Delta differences in distribution as well as differences in trait expression are considered. Showing these characteristics Delta is especially suited to compare the differentiation of collectives with respect to phenotypic and genetic traits. Thus the description of adaptive capacities is possible. Therefore Delta can be used well to analyse the breeding progress in the context of sustainable breeding. An application of Delta in the course of a test of hypotheses based on simulation studies is demonstrated.In the second, experimental part of the thesis phenotypic and genetic traits of plants of a Norway spruce clonal test of the Department of Forest Genetic Ressources of the Lower Saxony Forest Research Institute are analysed exemplarily. The growth of 152 clones and a seedling standard are analysed over 18 years on six test sites. The clones are characterised at nine polymorphic enzyme gene loci additionally.Based on the data of the clonal test norms of reaction of genotypes are compared. The material is especially usefull to analyse questions of success of selection with respect to the trait in focus of breeding and the genetic changes caused by viability selection as well as breeding selection. The changes of associations of phenotypic trait expression and genetic structures through viability selection and breeding are quantified and compared. Thus the sustainability of the breeding activity is investigated exemplarily.Changes of the genetic structure over time indicate viability selection at the level of the genetic background. Breeding selection results in reduction of the genetic variation at the nine enzyme gene loci. Nevertheless the null hypothesis of absence of genetic selection at the genetic background through breeding cannot be rejected. For the enzyme gene locus NADH-dehydrogenase a link between the traits survival and growth can be shown exemplarily thus demonstrating potential effects of phenotypic selection on the variation of the genetic background.The application of methods developed in the first part of the thesis on the Norway spruce breeding program allows for an evaluation in the context of sustainable breeding. The little change of the genetic background can be taken as positive. The saveguarding of adaptive capacities is put into relation with the necessary changes of the genetic structure in the course of the breeding program. Possible compromises for the actual breeding program are mentioned. Finally the connection of the methods of sustainable breeding with a self sufficient system of breeding through utilisation is discussed.