Interspecies Hybridization Barriers of Impatiens
Date Issued
2011
Date
2011
Author(s)
Wang, Yi-Lin
Abstract
Impatiens walleriana Hook.f is one of the most important bedding plants in Taiwan or worldwide. In Taiwan, there are three native Impatiens species, I. devolii Huang, I. tayemonii Hayata, and I. uniflora Hayata, could be used as breeding materials. Self- and inter-specific pollination between three native Impatiens and Impatiens walleriana Hook.f ‘Accent Rose’ were investigated in this study. The objectives were to investigate 1) the native Impatiens species growth behavior under natural conditions at Mei-Feng area, 2) anther dehiscence, pollen germination rate, and changes in stamen-pistil relative position during flowering, 3) in vivo pollen tube growth, developments of ovary, ovule and embryo, and thus to clarify hybridization barriers in Impatiens. Hybrid embryos were cultured to rescue possible inter-specific progenies.
Under natural conditions in Mei-Feng area, seeds of Impatiens devolii Huang germinated in March and April. In late June, young plants grew rapidly and flowered in July and August. For Impatiens tayemonii Hayata, the seeds of germinated between November and March, the seedlings could tolerate the cold winter and continued to grow. Young plants grew rapidly from March and mature plants flowered from May to October. For Impatiens uniflora Hayata, there were seed- and rhizome- propagations. Both seed germination and rhizome sprouting occurred in March. Mature plants flowered in July and August. Capsules of the three species matured about 20 days after self-pollination and. Old plants senescenced when winter was came.
The pistil of Impatiens species was surrounded by the filaments. For I. devolii Huang the anther just located in frount the pistil, and the stigma elongated and entered to the anther at anthesis. The stigma of I. tayemonii Hayata, I. uniflora Hayata and I. walleriana Hook.f ‘Accent Rose’ was surrounded by the filaments, and the anther was beside the pistil. a And the stigma did not reach the anther in I. tayemonii Hayata, I. uniflora Hayata and I. walleriana Hook.f ‘Accent Rose’ during the flowering process.
The Brewbaker and Kwack (BK) medium containing 10%-15% sucrose was suitable for pollen germination of I. devolii Huang. Water bath temperature of 10 to 30 ℃ did not affect pollen germination rate. Pollens obtained at anthesis had the highest germination rate. Pollens of I. tayemonii Hayata germinated well on BK medium containing 10%-15% sucrose at 10 to 35 ℃, with highest rate at 20 ℃. Pollens obtained one day after anthesis had the highest germination rate. Pollens of I. uniflora Hayata germinated well on BK medium containing 0%-10% sucrose. Pollens could germinate at 30-35 ℃ but germinate better at 10 to 25 ℃. Pollens obtained one or two days after anthesis had the highest germination rate. Pollen of I. walleriana Hook.f ‘Accent Rose’ could germinate well on BK medium containing 0%-5% sucrose, the optimum germinate temperature was 25 ℃, and the highest pollen germination rate was two days after anthesis.
Pollen tubes could all be observed at the pistils and ovules 24 h after self- and inter-specific pollinating between I. devolii Huang, I. tayemonii Hayata, I. uniflora Hayata and I. walleriana Hook.f ‘Accent Rose’. There were no pre-fertilization barriers among these four parents. Paraffin section revealed that all self-pollinations resulted in well-developed embryos. The embryos could only reach the globular stage in cross-pollination between I. tayemonii Hayata and I. uniflora Hayata, and between I. tayemonii Hayata with I. walleriana Hook.f ‘Accent Rose’, and did not reach beyond pro-embryo stage for other cross-pollinated combinations. All cross-pollinated embryos failed to develop further and aborted 12 days after pollination. The ovules were taken 7, 9, and 11 days after pollination from crossing I. tayemonii Hayata with I. walleriana Hook.f ‘Accent Rose’ and cultured on Nitsch and Nitsch medium containing 30 or 60 g∙L-1 sucrose. All ovules became browning within 20 days when cultured in vitro.
Subjects
Impatiens devolii Huang
Impatiens tayemonii Hayata
and Impatiens uniflora Hayata
embryo development
embryo rescue
Type
thesis
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