温度介导的母体效应调控结缕草种子复合休眠的功能及机制研究

Zoysiagrass (Zoysia japonica) is a widely distributed warm-season turfgrass. However, the compound dormancy nature of the grass seeds severely limits its promotion and application. In addition to its own genotype, the maternal effect mediated by environmental temperature during seed development is an important factor that affects Z. japonica seed germination. A previous study found that there is a wide range of genetic variation in the dormancy of Z. japonica seeds, and it is related to its flowering stage. However, the effect of maternal effect on the dormancy of Z. japonica seeds, its pathways and mechanisms are still unclear. In this project, a different dormant Z. japonica that was obtained from the previous screening was studied. The maternal plants were temperature-treated from the initial flowering stage to the seed maturity. The effect of the maternal temperature on the dormancy characteristics of the mature seeds was analyzed. Physiological dormancy genotype variation induced by physical dormancy and embryos were studied separately. Tissue structure at different stages was examined by electron microscopy and paraffin sectioning in order to reveal the effect of water permeability on the seed coat. In addition, gibberellin acid, abscisic acid and related gene expression patterns at different stages of seed development were tested. The implementation of this project clarified the regulatory pathway and mechanism of temperature-mediated maternal effect on seed dormancy, and theoretical support was provided for breeding new Z. japonica varieties that are adapted to environmental changes.

结缕草是分布广泛的暖季型草坪草，然而其种子的复合休眠严重限制了结缕草的推广应用。除自身基因型，种子发育过程环境温度介导的母体效应是影响种子萌发的重要因素。前期工作发现结缕草种子休眠存在广泛的遗传变异，且与其开花期存在相关性。然而，母体效应对结缕草种子休眠的影响及作用途径和机理尚不明确。本项目以前期筛选获得的不同休眠型结缕草为研究对象，在初花期至种子成熟对母体植株进行温度处理，研究①母体温度效应对子代成熟种子休眠特性的影响，分析颖苞引致的物理休眠和种胚引致的生理休眠基因型变异；②通过电镜扫描及石蜡切片观察颖苞不同发育阶段组织结构，揭示颖苞透水透气性的影响；③种子发育不同阶段种胚赤霉素、脱落酸含量变化规律及相关基因表达模式。通过本项目的实施，明确温度介导的母体效应对种子休眠的调控途径及作用机制，并为培育适应环境变化的新品种提供理论支持。

结缕草由于其较高的坪用性能和优良的抗逆性，成为我国主要的绿化及运动场草坪草之一。结缕草种子的休眠严重限制了在生产中的应用价值和建植效率。种子的休眠除了受到自身基因型控制，还受到母体植株发育过程中环境条件的影响，这种母体效应对结缕草种子的休眠性的影响尚不明确。本项目从全世界范围内收集野生结缕草种质资源，并对15个品系在不同温度条件下的休眠性进行了评价。明确了野生结缕草种质休眠性变异系数达到48%。分别对高休眠型WZG123和低休眠型WZG46在结实过程进行不同温度处理，子代种子休眠受到母体效应的影响。在24/16℃下结实种子，在30℃下发芽率较16/8℃母体环境高16%。即结实过程母体环境温度较高，则子代种子发芽率在温度较高时休眠较低。对子代种子休眠释放过程中，ABA含量随着发芽进程显著下降，种胚呼吸强度和脱氢酶含量随休眠释放过程而增加。低温层积4周也能显著促进种子的休眠释放，WZG123子代种子发芽率提升18%。外源赤霉素处理对F0代及不同温度处理收获的F1代种子表现出相同的效果，在300μmol/L的浓度处理下，种子平均发芽率提升了32%。种子成熟过程中温度信号的传递是生态适应性的重要途径，本研究证明母体效应同基因型共同作用调控子代种子休眠特性，从而选择适宜的发芽时机，对于培育在复杂多变的成熟环境中持续提供高质量种子作物具有重要意义。