孕穗期低温导致小麦小穗不育的生理机制

Low temperature stress at winter wheat (Triticum aestivum L.) booting stage is one of the main meteorological disasters in Yangtze River and south of Huang-Huai region. In some areas wheat yield could be decreased more than 30% in severe disaster-suffered years. The spikelet sterility is the main cause of yield reduction, and the physiological mechanism of spikelet sterility caused by low temperature at booting stage is unclear. In the present program, we intend to choose different cold sensitive varieties of wheat for low temperature treatment in artificial climate chamber at booting stage. After exposure to low temperature, observing the morphological and cytological characteristics of spikelet, floret and vascular, to define the damage of low temperature on wheat panicle development at booting stage; Measuring the photosynthetic carbon product distribution and sucrose content in spikelet at different spike position, and analyzing the activities of enzymes involved in sucrose metabolism and the expression of key enzymes in metabolism in floret, to prove up physiological mechanism of sucrose metabolic effects on spikelet, floret degeneration; Discussing the effects of endogenous hormone content and balance on sucrose metabolism and spikelet sterility. Based on the above results, this research would focus on the changes of sucrose metabolism and hormone level to reveal the physiological mechanism of spikelet sterility after exposure to low temperature at booting stage. The research results would provide theoretical basis for breeding wheat varieties resistant to low temperature in spring and exploring the cultivation measures of reducing low temperature injure.

孕穗期低温是黄淮南部及长江中下游麦区小麦生产上的主要气象灾害之一，受灾严重年份减产可达30%以上，小穗不育、穗粒数减少是产量损失的主要原因，孕穗期低温造成小穗不育的生理机制尚不明确。本研究拟选择不同低温敏感型小麦品种为材料，孕穗期于人工气候室内模拟低温胁迫，观测小穗、小花和维管束形态及细胞学特征，明确孕穗期低温对小麦幼穗发育造成的伤害；测定不同穗位小穗中光合碳产物分配、蔗糖含量，分析小花中蔗糖代谢相关酶活性及代谢关键酶基因的表达特征，探明蔗糖代谢影响小穗、小花退化的生理机理；探讨小穗中内源激素含量变化和平衡关系对蔗糖代谢和小穗不育的调控作用。研究主要以小穗蔗糖代谢和激素水平变化为核心，揭示孕穗期低温造成小麦小穗不育的生理机制，为选育抗春季低温的小麦品种和探索抗寒调控栽培措施提供理论依据。

孕穗期低温是黄淮南部及长江中下游麦区小麦生产上的主要气象灾害之一，受灾严重年份减产可达30%以上，小穗不育是产量损失的主要原因。本项目选择了不同低温敏感型小麦品种为材料，孕穗期于人工气候室内模拟低温胁迫，探究孕穗期低温导致小麦小穗不育的生理机制。结果如下：（1）孕穗期低温胁迫后，小麦小穗和小花发育迟缓，花粉粒败育数量增加，维管束数目降低。（2）低温降低了旗叶吸收CO2的能力，旗叶中13C丰度和旗叶向籽粒转运的13C下降，影响了光合产物从旗叶向籽粒中的转运能力。（3）低温胁迫后，幼穗中蔗糖含量呈上升趋势，磷酸蔗糖合成酶（SPS）活性呈上升趋势；蔗糖合酶（SuS）活性在4℃和2℃处理后呈上升的趋势，且与对照间的差异达显著水平（P＜0.05），随着胁迫温度的降低，SuS活性呈现下降的趋势，葡萄糖焦磷酸化酶（UGP）活性与转化酶（Inv）活性均随胁迫温度的下降而降低。蔗糖合酶基因TaSuS1 表达量下调，TaSuS2表达量上调；细胞壁转化酶基因IVR1 和液泡转化酶基因IVR5表达量下降。（4）低温胁迫后，小麦幼穗中脱落酸（ABA）含量呈上升趋势，生长素（IAA）和赤霉素（GA3）含量呈下降趋势。（5）低温胁迫后，小麦籽粒饱满度降低，籽粒中腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)、可溶性淀粉合成酶（SSS）、束缚性淀粉合成酶（GBSS）和淀粉分支酶（SBE）活性在灌浆期整体呈下降趋势，尤其是GBSS和SBE活性下降幅度较大。（6）低温胁迫后，小麦籽粒淀粉累积速率随处理温度的降低逐步下降，淀粉含量也随之下降。籽粒灌浆持续期延长，最大灌浆速率出现的时间推迟，平均灌浆速率和最大灌浆速率下降，籽粒干物质质量下降。籽粒成熟期的穗粒数和千粒重均显著下降下降。本项目研究成果揭示了孕穗期低温造成小麦小穗不育的生理机制，为选育抗春季低温的小麦品种和探索抗寒调控栽培措施提供理论依据。