Enhancing production of high-quality seed in Swedish conifer breeding
1996
Eriksson, U. (SLU, Uppsala (Sweden). Inst. foer Skogsgenetik)
The main objective of this work was to develop and evaluate methods for increasing genetic control in the production of improved material in field-grown seed orchards. Supplemental mass pollination (SMP) and flower induction (stem injection of gibberellin A4/7) were studied in two Pinus sylvestris L. orchards, while flower induction (stem injection of the gibberellin and root pruning) were studied in three orchards of Picea abies (L.) Karst. SMP success rates, studied by means of allozyme markers, varied between 66% and 84% in a methods study in which pollen was applied close to each single strobilus. A single pollination of a strobilus at peak receptivity was sufficient to obtain high success rates. Success rates varied between 10% and 69% in four operational SMP experiments in which pollen was dusted over whole grafts. To increase success rates whole grafts should be pollinated more than once during each of a number of consecutive days. Root pruning significantly increased female flowering in two of the P. abies orchards, while stem injections of the gibberellin induced a significant increase in one of these orchards. In two orchards the increase in number of cones was approximately threefold. Neither treatment had a significant effect on male flowering, and no interactions were found between treatments in the P. abies orchards. Stem injections on P. sylvestris grafts significantly increased seed and pollen production in one experiment each. Seed weight was significantly reduced by the stem injections in both P. sylvestris orchards. Significant clonal differences were found for all tested variables. No damage on the grafts was found that could be attributed to the gibberellin treatments. The results indicate that SMP and flower promotion methods can have practical value in seed orchard management. However, a full exploitation of the potential genetic gain from the improvement of the breeding populations will require the development of seed production concepts more advanced than those upon which current orchards are based.
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