Successful Fertilization and Seed Set from Pollination on Immature Non-dehisced Flowers of Eucalyptus globulus

Abstract

To minimize the number of visits required to achieve seed-set from hand pollination whilst maintaining full control of the reproductive process in Eucalyptus globulus, we investigated the importance of style maturation on the progamic phase of reproduction. Controlled pollinations were performed in: (1) fully receptive styles; (2) immature cut styles at or after flower dehiscence; and (3) immature cut styles before flower dehiscence. We show here that pollen germination and tube growth to the ovule occurred in all three treatments, and all produced viable seeds. Remarkably, tubes growing on immature sliced styles of non-dehisced flowers reached the ovules by day 7, 1–2d faster than tubes growing on normal receptive stigmas. Moreover, more tubes entered the ovary in this kind of pollination and, consequently, more viable seeds were produced. We established histochemically that tube growth in immature sliced styles is concomitant with the presence of lipid secretion. These results fully support the efficiency of the so-called ‘one-step pollination’ method in Eucalyptus globulus, which we now prove can be applied more successfully to immature non-dehisced flowers. General application of this procedure is likely to have beneficial impacts on the planning and efficiency of large-scale genetic improvement programs.