光调控套作大豆分枝发育的生理机制

Intercropping system is one of the effective agronomic measures to solve the problems such as shortage of soybean planting area and the gap between supply and demand. But in the intercropping system, shade at seedling stage leads the soybean to undesired phenotypic changes such as excessive main stem elongation, less branching and lower yield. Previous studies have found that the yield of intercropping soybean is determined by the number of branches per plant directly, but the physiological mechanism of the soybean branch growth effected by the shading condition is unclear. In this study, two soybean cultivars with different sensitivity and branch number to the shading condition will be used as research materials. Combining laboratory and field experiments, the method and technology of plant physiology and molecular biology will be applied to resolve scientific problem of crop cultivation. In order to clarify the relationship between the stem configuration and light utilization under the shade condition, the branch growing process of different soybean cultivars, light intercepting and photosynthetic performance of leaves in different canopy position will be investigated. The physiological process of the interaction between the shading condition and endogenous hormones metabolism will be studied to clarify the role of the strigolactone and the synergism with other hormones in the development of soybean branches. For the purpose of exploring genetic difference locus in the hormone metabolic pathway of different soybean cultivars when their branch growth is effected by shade stress, the spatio-temporal expression of the genes involving the biosynthesis and signal transduction of strigolactone will be analyzed. By means of this study, we assume that we can provide the theoretical support for molding ideotype of intercropping soybean, screening adaptive cultivar and developing high-yield cultivation technology.

间套作是解决我国大豆播种面积不足、供需缺口大的有效措施之一。但在套作系统中，苗期荫蔽导致大豆主茎过度伸长、分枝数减少、产量降低。前期研究发现，分枝多少直接决定套作大豆产量高低，但荫蔽环境影响大豆分枝形成的生理机制尚不清楚。本项目以对荫蔽敏感性不同的大豆为材料，室内与田间试验相结合，将植物生理学和分子生物学的方法与技术应用到作物栽培研究中，对荫蔽环境下不同基因型大豆分枝发生过程、冠层内不同部位光截获和叶片光合性能进行研究，明确荫蔽环境下大豆茎秆构型与光能利用的关系；研究荫蔽与内源激素互作调控分枝发育的生理过程，阐明独脚金内酯协同生长素和细胞分裂素在大豆分枝发育过程中的作用机制；并对不同荫蔽敏感型大豆材料的独脚金内酯代谢与信号转导过程中的关键基因时空表达进行分析，明确不同基因型大豆响应荫蔽胁迫的基因差异位点，为套作大豆理想株型塑造、品种筛选和高产栽培技术研发提供理论支撑。

为揭示玉米大豆带状复合系统中，因玉米遮荫导致大豆主茎过度伸长、分枝数减少、产量降低的原因，本项目以对荫蔽敏感性不同的大豆为材料，分析了不同基因型大豆分枝形态与光能利用、产量、独角金内酯、生长素等激素及基因的关系。证实了在荫蔽下可以通过增加分枝数量从而提高产量，同时发现，在玉米-大豆带状复合种植模式下，一方面，光敏色素相关基因PhyB的下调促进了GmMAX家族基因的上调，导致遮荫环境下独脚金内酯含量的增加。另一方面，光敏色素相关基因PhyA的上调抑制了生长素的合成，下调了GmPIHI基因的表达，从而影响了生长素的反应。这两种作用都抑制了大豆枝条的形态发生。进一步，找到了在植物分枝调控中发挥重要作的独脚金内酯信号通路重要基因GmSMXLs，该基因可以负向调控独脚金内酯信号的接收和响应，从而影响遮阴胁迫下分枝发生的能力。 以上研究结果，弄清了光环境变化、大豆茎秆（主茎和分枝）建成和光能高效利用三者的相互调节关系；从内源激素代谢角度，揭示大豆分枝形成受荫蔽环境调控的生理机制；明确荫蔽环境与激素互作过程中，独脚金内酯在大豆分枝形成中的作用；最终找到荫蔽环境下影响大豆分枝发育的关键功能基因。本项目基础上形成了光环境、基因型与激素三者有机结合的带状复合种植低位作物株型调控理论，为突破大豆倒伏低产瓶颈和挖掘耐荫抗倒资源提供了理论支撑；对塑造套作大豆理想株型和研发大豆高产栽培技术，具有重要的科学意义和应用前景；形成成果“玉米大豆带状复合种植技术体系创建与应用”获四川省科技进步一等奖 ，成果“大豆-玉米带状复合种植技术模式集成创新与示范推广”农业农村部农林牧渔丰收奖，同时培养毕业硕士研究生 4 人，在读博士研究生 2 名，发表研究论文4篇，省级审定大豆品种2个（川农夏豆1号、川农夏豆3号），授权国家发明专利、实用新型专利和软件著作权各1项。