EMBRYOGENESIS AND ENDOSPERMOGENESIS IN INTERGENERIC HYBRIDIZATION BETWEEN Calibrachoa- Petunia

Abstract

In ornamental crops, intergeneric hybridization is limited by different incompatibility barriers that are established after fertilization. The objectives of this work were to know at a histological level how the incompatibility manifests itself in the combination of Petunia inflata x Calibrachoa x hybrida var. Kabloom yellow; identify the optimum timing to rescue embryos during the embryogenesis process; and determine the stage of development of the embryo and endosperm in which postzygotic incompatibility manifests. Crosses were made between Petunia inflata and Calibrachoa x hybrida var. Kabloom yellow. For observation through histological sections of developing seeds, paraffin inclusions were made from fruits harvested from 3 to 10 days after pollination (DPP), and for observation of mature seeds, fruits prior to dehiscence were collected and seeds were cut longitudinally under a magnifying glass. It was observed that the endosperm stops its division at 5 DPP, and no presence of embryos is observed at 7 DPP. On the other hand, manually cut seeds showed development of the integument and absence of embryo and endosperm. In these seeds, incompatibility is manifested through the elimination of cells by programmed cell death, which leads to autolysis of the embryos and the endosperm, and finally to the formation of empty seeds. Therefore, the rescue of proembryos at 5 DPP could be a good technique to overcome postzygotic reproductive barriers.