Zmienność obradzania szczepów na plantacji nasiennej modrzewia europejskiego (Larix decidua Mill.) w Sękocinie Starym

The genetic diversity of seed orchards is assessed by the effective number of clones. The effective number of clones is an indicator that is usually calculated based on the frequency of ramets in the clones. In this study, this parameter was compared by additionally calculating it only for the cone-producing ramets. The aim of this study was to determine the contribution of clones to cone production in the European larch seed orchard in Sękocin Stary in 2022. The cone production of individual clones growing in the seed orchard was analysed. Cones were collected from all larch ramets (trees). Of the 240 trees planted, only 186, representing a total of 40 clones, produced cones. The cones of each tree were counted and weighed individually. It was found that clone no. 19 produced the most cones with a yield of 1,493 cones, representing 8.13% of the total seed orchard. Clone no. 26 produced the lowest yield with only 14 cones from five trees (0.08% share of cone production). Analysis of variance showed the significance of differences between clones for the mean number of cones (p = 0.0003) and for the mean cone weight (p = 0.0002) for the clones. The effective number of clones was Nc = 37.97 for the trees with cones and 39.49 for all trees (originally planted), excluding crops. The relative effective number of clones for trees/ramets with cones was Nr = 0.95. Despite a high value of Nr, the clones in the studied seed orchard differed significantly in their contribution to cone crop in 2022. In order not to limit the genetic variability of forest reproductive material from seed orchards, cones should also be collected from trees that produce few cones.