Zygotic embryogenesis and empty seed formation in European larch (Larix decidua Mill.)

Abstract

Zygotic embryo development and its influence on empty seed formation of the European larch (Larix decidua Mill.) was studied within a seed orchard in the Slovak Republic. Histological study revealed a fertilization date early June. Although embryogenesis was most intensive in June, fully morphologically differentiated embryos were observed no earlier than in the second half of July. Multiple fertilization and simple polyembryony were relatively rare but their frequencies correlated with the efficiency of pollination. Only a small percentage of developing embryos reached full maturity. Degeneration included suppressed embryos from polyembryony as well as normal embryos occupying the optimal position within the corrosion cavity of the female gametophyte. The mean proportion of fertilized ovules without a viable embryo was 61% after open pollination and as high as 88% after controlled selfing. In total, embryo degeneration reduced the potential full seed percentage by almost 40% and is therefore considered the most important cause of unsound seed development in European larch. © INRA, EDP Sciences, 2005.