利用重组自交系籼稻中-156/谷梅2号304份株系为材料，在田间条件下营造高温、高湿的小气候，以“穗穗芽率”及“粒穗芽率”为指标，筛选易发生穗芽与不易发生穗芽的极端材料，比较研究重组自交系亲本与各供试株系籽粒在穗芽发生期间的生理差异。结果表明，该重组自交系母本谷梅2号比父本中-156易穗芽，在正常成熟过程中籽粒内源GA1含量水平高于中-156，ABA含量水平低于中-156；谷梅2号籽粒淀粉酶活性也高于中-156。花后15 d至完熟的籽粒灌浆期如遇高温、高湿条件，谷梅2号及易穗芽的株系籽粒内源GA1随雨日渐增，增幅高于中-156及不易穗芽的株系，同时其淀粉酶活性回升，在正常成熟过程中花后15 d后籽粒中淀粉酶活性与日渐降，但其幅度远高于父本中-156及不易穗芽的株系，这种变化可能是易穗芽的亲本与株系对高温、高湿敏感诱发穗上发芽的主要生理基础。
“Pre-harvest sprouting” in rice is usually caused by high temperature and humility or continuous raining. It has frequently happened in F1 in hybrid rice seed production. Those “Pre-harvest sprouting” or “Physiologically germinated” seeds are of lower quality, by which the hybrid rice seed production is badly affected, and the problem usually happens every three years. 20% or even 50% yield in the seed production losts by “Pre-harvest sprouting” in the Yangtze River and the South West areas. It is estimated that “Pre-harvest sprouting” causes an average decrease of seed activity by 10%.
A recombinant inbred line (RIL) population comprising 304 lines derived from a cross between indica rice (Oryza sativa L.) cultivars Zhong-156 and Gumei-2 was used to study the physiology of pre-harvest sprouting.
Based on the data of “Sprouting rate in panicle” and “Sprouting rate in grain”, two kinds of lines namely easy-sprouting lines and hardly-sprouting lines were selected to investigate their physiological differences when pre-harvest sprouting happened.
The experiment was conducted in a special field with higher temperature and higher humidity microclimate. The results indicated that female parent GM-2 was easier to produce pre-harvest sprouting than the male parent ZH-156, GA1 content and amylase activity in GM-2 grains were higher than that in ZH-156. However, ABA content in GM-2 grains was lower than that in ZH-156. Higher temperature and higher humidity facilitated the GA1 increment from milk ripe stage to yellow ripe stage, GM-2 and the easy-sprouting lines showed a even higher span of increase tendency than ZH-156 and the hardly-sprouting lines, which enhanced amylase activity and led to pre-harvest sprouting. This may be the physiological basis for pre-harvest sprouting induced by higher temperature and higher humidity, and these special characters must be inherited from their parents.
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