Loss of alleles due to resistance breeding: The case of cypress

Individuals were selected for resistance against the imperfect fungus Seiridium cardinale Wag in six populations of Mediterranean cypress (Cupressus sempervirens L.). The collections of resistant clones and their base populations were surveyed at several isozyme gene loci. A total of 140 adult trees and of 109 clones were genotyped at six isozyme gene loci. The comparison yielded information on changes in genetic variation due to artificial selection. The genetic structure of most clone collections were similar to their base populations. Nevertheless, the number of rare alleles among the resistant clones had consistently decreased, although the numbers of investigated trees were similar to those of the clones. Possible implications for breeding strategies are discussed.

Presentation during the international conference: "Dynamics and conservation of genetic diversity in forest ecosystems", Strasbourg, 2-5 December 2002