Evaluation of Pollen Tube Growth and Fertilization via Histological Analysis in Cyclamen Persicum

Abstract

Embryo rescue plays a considerable role for modern breeding techniques. It is used to overcome embryo degeneration after interspecific hybridizations, distant hybridization or after pollination with irradiated pollen grains. In some genera such as Cyclamen, however, it is technically not possible to take embryos out of the ovules. Therefore, whole ovules or even ovaries are cultured instead of embryo rescue. For these cultures, the determination of the exact period of zygote/embryo formation is crucial. In the current study, pollen viability, fertilization, pollen grain germination and zygote formation were investigated in wild and commercial Cyclamen persicum. Flower buds were emasculated before anthesis stage and pollens were isolated. Flower buds were collected after hand pollination with own pollen in 24 h intervals during 9 days after pollination in order to scan pollen germination in the stigma and pollen tube growth. Pollen viability rates were estimated using tetrazolium and in vitro pollen germination methods. Pollen tube growth and fertilization were scanned with fluorescence microscopy after staining samples with aniline blue. Zygote formation period determined by sectioning of paraffin-embedded flower buds collected at the 10(th), 20(th), 30(th) and 40(th) day after pollination. According to the results, pollen viability rates were 82.1-84.3% and in vitro germination rates were 63.8-65.2% in both, the commercial cultivar and the wild cyclamen genotype respectively. Fertilization occurred in the first two days after pollination in wild cyclamen, while pollen tube reached the ovary between 5 and 7 days after pollination in commercial cultivars. Zygote formation were detected at day 20 after pollination in wild cyclamen, while occurred between the 30th and the 40th days in commercial cultivar.