EVIDENCE OF AN UNBALANCED MATING PATTERN IN A SEED ORCHARD COMPOSED OF 2 LARCH SPECIES

Mating patterns of a larch seed orchard composed of one clone of Larix sibirica and 6 clones of L. decidua, were investigated using allozyme s as genetic markers. The studied orchard was designed to produce inte rspecific hybrid seeds. It was found that the orchard constitutes a po pulation with a mating system that is far from panmixis. Studying outc rossing rates of individual clones by the mixed-mating model, some of the symptoms of non-random mating could be detected. They ranged betwe en 0.096 for the Siberian larch clone, and 0.952 to 1.019 for the Euro pean larch clones. However, the most profound insight into the mating patterns was possible through the use of the mating model methods. Det ailed mating model analyses revealed that the Siberian larch pollinate d almost 93% of all sampled ovules, while the remaining European larch es only 7%, with some clones contributing less than 0.2% of all pollen gametes. The effectiveness of Siberian larch as a pollinator could be explained by its high flowering abundance and earlier flowering pheno logy, as well as by the specific design of the orchard, where a half o f the grafts were of Siberian larch. The neighborhood model (variant o f the mating model) applied in this study indicated that fecundity of males and their distance to maternal trees significantly influenced ma le mating success. The mating model studies allowed also for an in dep th analysis of the hybridization pattern between the 2 species. Its le vel for European larches functioning as females averaged on 93.9%, whi le only 10.5% Siberian larch seeds were hybrids, which has significant implications for forest tree improvement programs. The advantages of applying the mating model approach in the studies of mating systems of forest trees, mainly seed orchards, are briefly discussed.