弱光下烯效唑对重穗型杂交水稻茎秆抗倒伏性的影响及其调控机理

The lack of light in the canopy induces reduction of stem lodging resistance, which is an important factor limiting heavy-panicle hybrid rice yield and quality in single rice of the Sichuan Basin. Previous study showed that uniconazole application reduced plant height and increased stem strength, and thus improved crops lodging resistance. However, information about stem morphology and culm tissue structure as affected by uniconazole under low light condition and its relationship to lodging resistance in heavy panicle type rice was still unclear. In this study, the field experiments were conducted: (1) the varieties with different panicle type rice and different shading treatments were used, (2) the uniconazole with different application levels were external applied under shading condition. The stem lodging related physical parameter, stem morphological traits, cell structure and the endogenous hormonal changes were measured. Also, cell wall structure, carbohydrates, cell wall components and gene expression related cell wall synthesis also be determined. The objective of this study was to determine the effect of uniconazole on lodging resistance in heavy panicle type rice under shading condition and the relationship among endogenous hormonal change, stem morphological traits, culm tissue structure and synthesis of cell wall in regulate the lodging resistance of heavy panicle type rice under shading condition.

四川盆地稻区是重穗型杂交水稻的主要种植区，但是该地区常年遭受阴雨寡照天气，尤其在水稻生育前期，群体内部光照不足，植株倒伏风险较大，是水稻安全生产的主要症结所在。研究表明，外源施用烯效唑降低株高和增加茎秆强度，进而提高作物抗倒伏性，但是弱光下烯效唑对重穗型杂交水稻茎秆抗倒伏性的影响和调控机制尚不清楚。本项目拟选用穗重型不同水稻品种，人工遮荫控制冠层光照条件，结合喷施烯效唑处理塑造抗倒伏性不同水稻群体。测定茎秆物理力学指标、茎秆形态、组织和细胞结构、碳水化合物、內源激素及细胞壁生物合成基因表达等，从细胞发育角度阐明植株內源激素变化对茎秆组织结构和形态建成调控途径，揭示烯效唑对茎秆细胞壁生物合成的调控及其对弱光的响应机制，研究结果将为化控技术协调重穗型杂交水稻高产与抗倒伏的矛盾，提供理论基础和实践依据。

弱光胁迫显著增加四川盆地稻区重穗型水稻倒伏风险。研究表明，烯效唑显著降低株高并增加茎秆强度，进而改善作物抗倒伏性。但是，弱光胁迫下烯效唑对重穗型水稻茎秆抗倒伏性的影响和作用机理尚不清楚。本研究选用穗重型不同的杂交水稻，人工遮阴控制冠层光照条件，结合叶源喷施烯效唑处理，测定茎秆力学指标、形态指标、碳水化合物、组织细胞结构和基因表达变化，分析烯效唑影响弱光下重穗型水稻抗倒伏的生理机制。结果表明，在一定株高范围内，缩短基部节间长度，适度增加上部节间长度，是协调重穗型水稻高产和倒伏风险矛盾的重要途径。较正常光照，遮阴显著降低杂交水稻产量，增加倒伏指数，归因于基节茎秆强度大幅减小，渝香203响应较为敏感。遮阴处理降低节间伸长初期IAA、Z+ZR、iP+iPA和GA1、GA3，是茎壁细胞层数减小，导致壁厚和茎粗降低的直接原因。此外，厚壁组织细胞壁形成过程中调控纤维素和木质素合成基因大幅度下调表达，使得茎秆机械组织和维管束结构疏松，是茎秆强度减小，倒伏风险增加的重要原因。叶源增加烯效唑显著降低植株倒伏风险，归因于株高缩短和茎秆质量增强，品种、遮阴和烯效唑对倒伏指数存在显著交互效应。烯效唑提高了节间伸长初期ABA含量，降低了GAs含量，使得细胞长度和基部节间缩短导致株高降低；此外，烯效唑提高了细胞分裂素（Z+ZR、iP+iPA）含量，使得薄壁组织细胞层数和壁厚有所增加。相关分析表明，烯效唑增加茎秆质量主要依赖于结构性碳水化合物（SC）。弱光环境下，烯效唑下调了渝香203厚壁组织细胞壁形成过程中基因表达水平，SC含量反而大幅增加，这归因于反馈调节机制；对于C两优华占，烯效唑促进了各基因表达，改善了木质素在次生壁中的积累和机械组织发育程度，从而增强了茎秆机械强度和抗倒伏性。综合分析，选择烯效唑浓度为40 mg/L于拔节初期进行叶面喷施是改善弱光下重穗型杂交水稻抗倒伏性的最佳措施。本研究结果将为化控技术协调弱光区重穗型水稻高产与倒伏风险矛盾提供理论技术和实践依据。