Interstock and grafting GA4/7 effects on flowering after topgrafting in Pinus sylvestris
Almquist, C. (The Forestry Research Inst. of Sweden, Uppsala (Sweden)) | Ekberg, I.
In breeding programmes shortening the generation turnover should increase the genetic gain per unit time. Topgrafting (in which scions of young trees are grafted into the crown of older, reproductively more mature trees) may help meet this objective, since it can induce young material to flower. Therefore, we studied the effect of the interstock clone on the flowering of topgrafts in Pinus sylvestris (L.) over three years. We also tested the possibility of enhancing female flowering among the topgrafts by treating the interstocks with gibberelin GA4/7. There were large differences in topgraft survival rates among the different interstock clones, varying between 54-89% in the third year. For both female and male flowering of the topgrafts, analysis of variance showed significant effects of both interstock and topgraft. The interaction between interstock and topgraft was significant for female flowering but not for male flowering. The lenght of the topgraft scion had a significant effect on the number of female flowering, causing a 55% increase in the number of flowers per topgraft in the third year. No relationship was found between the female flowering of the interstocks and their capacity to induce female flowering in the topgrafts. The results indicate that topgrafting could effectively decrease time to flowering compared to conventional grafting using young rootstocks in Pinus sylvestris
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