栽培菊花‘奥运天使’与野路菊杂交生殖障碍的细胞学机理

Cellular Mechanism of Reproductive Barrier During Cross Breeding Between Dendranthema grandiflorum cv.Aoyuntianshi and D.japonense

【目的】揭示栽培菊花与野生菊杂交结实率低,严重影响野生资源优异基因利用的原因。【方法】以栽培菊花‘奥运天使’(Dendranthema grandiflorum‘Aoyuntianshi’)为母本,菊属野生种野路菊(D.japonense)为父本,在人工杂交前利用花粉离体培养方法对父本花粉活力进行测定。在人工杂交后不同时间,对母本的雌蕊分别进行取样固定,并利用苯胺蓝染色法和常规石蜡制片技术对授粉后花粉在柱头上萌发行为及受精后胚胎发育状况进行研究。【结果】父本花粉活力为10.0%;人工授粉后0.5～8h,随着时间延长,花粉在柱头上萌发数量逐渐增加,但增加幅度很小,到授粉后8h时,平均每个柱头萌发的花粉数只有16.1粒。但此后,大量花粉开始萌发,在授粉后12h时,平均每个柱头上萌发的花粉数达到40.2粒。到24h时,柱头上花粉平均萌发数量达到最高,为51.5粒。随后柱头上萌发花粉的数量开始降低,到授粉后48h时,柱头上平均萌发花粉数量降为42.3粒。随着胚胎发育的进行,大量胚胎异常降解,使正常胚胎的比例逐渐降低,其中球形胚阶段正常胚胎比例为26.7%,心形胚阶段为18.3%,鱼雷胚阶段为14.4%,子叶胚阶段为10.6%,最终杂交结实率仅为7.6%。将已去雄的花序在开放条件下自然授粉,发现结实率高达51.4%。【结论】花粉活力及花粉在柱头的萌发行为对杂交结实率影响不大。杂种不活,即大量胚胎在发育过程中异常降解,可能是引起‘奥运天使’与野路菊杂交结实率较低的主要原因。

Our aim is to reveal the factors resulting in low seed set during chrysanthemum breeding and seriously influencing utilization of its wild germplasm. [ Method ] The interspecific distant hybridization was carried out between Dendranthema grandiflorum cv. Aoyuntianshi （female parent） and D. japonense （male parent）. In addition, pollen viability of male parent was tested in culture medium just before pollination, and germination behavior of pollen grains on the stigma after pollination was examined using aniline blue staining method. In addition, embryo development after fertilization was observed with technique of paraffin section. [Result] Pollen viability was 10.0% just before pollination. The average number of pollen grains germinating on stigma increased slowly between 0.5 h and 8 h after pollination, and 16.1 pollen grains germinated on each stigma at 8 h after pollination. But after that, a large number of pollen grains germinated, and the number was 40.2 at 12 h after pollination. At 24 h after pollination, the number reached the highest value, 51.5. Subsequently, the number began to decrease and dropped to 42.3 at 48 h after pollination. During the process of embryo development, the percentage of normal embryos decreased gradually due todegeneration of many embryos and the values were 26.7% at stage of globular embryo, 18.3% at stage of heart embryo, 14.4% at stage of torpedo embryo, and l 0.6% at stage of cotyledon embryo, respectively. Seed set in the artificial crossing was 7.6%, but the number under open pollination conditions was 51.4%.[Conclusion] Pollen viability of male parent and germination behavior of pollen grains on stigmas have no significant effect on seed set in the artificial crossing. And hybrid inviability, i.e. the degeneration or abortion of a large number of embryos during their developmental processes, may be the main factor leading to low seed set during cross breeding between D. grandiflorum cv. Aoyuntianshi and D. japonense.