National Institute of Crop Science, National Agricultural and Food Research Organization, 2-1-18 Kannondai, Tsukuba, Ibaraki, Japan.
Ann Bot. 2010 Sep;106(3):515-20. doi: 10.1093/aob/mcq124. Epub 2010 Jun 21.
High temperatures over 32-36 degrees C at anthesis induce spikelet sterility in rice. The use of a germplasm with an early-morning flowering (EMF) trait has been hypothesized as a way of avoiding this problem. In this study, the effect of the EMF trait on avoiding high temperature-induced sterility at anthesis by flowering at a cooler temperature in the early morning was evaluated.
The EMF trait was introgressed from wild rice (Oryza officinalis) into the rice cultivar 'Koshihikari' (O. sativa). First, spikelets of the EMF line and Koshihikari were subjected to rising temperatures during the daytime in the greenhouse to test for differences in spikelet sterility. Secondly, spikelets of both plants were exposed to 26, 34 and 38 degrees C at anthesis and to 38 degrees C beginning at least 1 h after flowering, in the growth chambers at 70 % relative humidity, to test for differences in tolerance to high temperatures.
Spikelets of the EMF line started and completed flowering a few hours earlier than Koshihikari. In a greenhouse experiment, spikelets of Koshihikari opened after the air temperature reached 35 degrees C, but those of the EMF line could open at cooler temperatures. Under these conditions, spikelet sterility significantly increased in Koshihikari, but did not in the EMF line. The number of sterile spikelets increased as their flowering time was delayed in Koshihikari. Furthermore, the chamber experiments revealed that 60 % of the spikelets from both lines were sterile when exposed to 38 degrees C at anthesis, indicating that tolerance of high temperature was similar in both genotypes.
Reduced sterility in the EMF line subjected to rising temperatures at anthesis in the greenhouse was attributed to an earlier flowering time compared with Koshihikari. The EMF trait of wild rice is effective in mitigating anticipated yield loss due to global warming by escaping high-temperature stress at anthesis during the daytime.
抽穗期温度高于 32-36°C 会导致水稻小穗不育。人们推测，利用具有清晨开花（EMF）特性的种质资源是避免这一问题的一种方法。本研究评估了通过清晨低温开花来避免高温诱导抽穗期不育的 EMF 特性的效果。
从野生稻（Oryza officinalis）中导入 EMF 特性到水稻品种 'Koshihikari'（O. sativa）中。首先，在温室中白天升高温度，测试 EMF 系和 Koshihikari 的小穗是否存在不育差异。其次，在生长室中，在 70%相对湿度下，将两个品种的小穗在抽穗期暴露于 26、34 和 38°C，并在开花后至少 1 小时暴露于 38°C，以测试对高温的耐受性差异。
EMF 系的小穗比 Koshihikari 早几个小时开始和完成开花。在温室实验中，当空气温度达到 35°C 时，Koshihikari 的小穗开始开花，但 EMF 系的小穗可以在较低温度下开花。在这些条件下，Koshihikari 的小穗不育率显著增加，但 EMF 系没有。随着 Koshihikari 小穗开花时间的延迟，不育小穗的数量增加。此外，室试验表明，当在抽穗期暴露于 38°C 时，两个系的小穗有 60%不育，表明两种基因型对高温的耐受性相似。
温室中抽穗期温度升高时，EMF 系小穗不育率降低归因于与 Koshihikari 相比更早的开花时间。野生稻的 EMF 特性通过在白天抽穗期逃避高温胁迫，有效地缓解了因全球变暖导致的预期产量损失。
