Parent-progeny relationship in Scots pine (Pinus silvestris L.)
Eklundh Ehrenberg, Carin
Three progeny tests with Scots pine (Pinus silvestris L.) including progenies from phenotypical plus and minus trees growing at different latitudes and altitudes were analysed. The progenies were obtained from crosses between the various tree types in a stand, between trees of different provenances, and after wind pollination and selfing. The characteristics analysed were total height, yearly height growth, branch length and branch angle, number of branches per whorl, length of apical bud, and length and number of lateral buds. The variation among the progenies seemed to be genetically controlled to a large extent but the varying environmental factors exerted a strong influence on the development of the young trees as well. No regular trend in the range among the plus and minus tree progenies in height growth was established when all progenies in each individual experiment were compared. Plus tree progenies were superior in height growth when compared to minus tree progenies of the same provenance. In two cases, plus tree progenies were inferior in growth rate. This was explained by an incorrect classification of the parent trees. In two out of three reciprocal crosses, significant differences in height between the reciprocal pairs were reported. Different combining ability or maternal influence are discussed as possible reasons for the differences. Four progenies obtained from the same mother tree after crosses with two plus trees, one minus tree, and after open pollination differed significantly in height. A great part of the variation between progenies is ascribed to the diversity of the male plus trees, in addition to the differences between plus and minus trees. One provenance cross between two plus trees of widely differing origin was superior in height growth to the open-pollinated progenies of the female as well as of the male parent tree. Four other provenance hybrids obtained from crosses between various minus trees did not exceed the open-pollinated progenies from the northernmost female parents in height. It is shown that the growth capacity of the parent trees used in provenance crosses is of great importance. A combination of two plus trees should result in better growing offspring than a cross between two minus trees. There was a strong correlation between the length of the terminal shoot in 1960 and the increase in height in 1961-1964. This indicates the possibility of selecting the best growing progeny at an early age. Significallt differences between progenies were established in most of the branch and bud characteristics analysed, indicating genetical control of these properties. The differences increased with increasing age of the progenies. There was a tendency for the plus tree progenies to have more slender crowns and fewer branches per whorl in the lower whorls as compared with minus tree progenies. The effect of inbreeding was manifested in slow height growth and poor vitality of the plants. No grouping by provenances was reported in the range of the progenies as regards branch and bud characteristics except in one experiment, where minus tree progenies of northern origin had narrower crowns than minus tree progenies from the southern provenance. On the whole, the phenotypes of the 20 selected plus and minus trees used as parents appeared to be closely related to the performance of their offspring as regards height grorth ability. The relationship between parent trees and offspring with respect to branching characteristics seemed to be less well defined. Correlations between parents and offspring in these characteristics cannot be estimated with the methods available at present.
Pinus silvestris; progeny tests; plus trees; minus trees; progenies; Sweden
Studia Forestalia Suecica
UKÄ Subject classification
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