Compatibility study in intergeneric crosses between Nierembergia and Calibrachoa
2013
In the present study, we report three methods to overcome pre-fertilization barriers in intergeneric crosses between Nierembergia and Calibrachoa, as a tool for ornamental plant breeding programs. Although pre-fertilization studies revealed the incompatibility among Nierembergia and Calibrachoa species, expressed in the pistil, four intergeneric combinations (N. scoparia × C. ovalifolia; N. scoparia × C. caesia; N. linariaefolia × C. thymifolia and N. linariaefolia × C. ovalifolia) were detected as putative crosses to obtain hybrids. Pollination was performed by three methods: 1) bud pollination, 2) cut-style pollination and 3) heating the style before pollination (50°C, for 2.5-5 min). When N. scoparia was used as the mother plant, the percentage of pollen tubes in the ovary increased significantly in the bud-pollination method and to a lesser extent when heating the style before pollination. In contrast, when N. linariaefolia was used as the mother plant, no pollen tubes were found in the ovary. On the other hand, the cut-style pollination method was not successful in the combinations evaluated because the absence of stigma affected pollen germination negatively. The results suggest that bud-pollination could be the best method to overcome pre-fertilization barriers in N. scoparia × C. ovalifolia and N. scoparia × C. caesia crosses. The results of the present study will serve as a basis for the future research of post-fertilization barriers, as a tool to obtain hybrids between both genera.
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