Background

Large panicle rice has a large sink capacity, but inferior spikelet filling is poor in this variety of rice due to asynchronous grain filling. The understanding of the factors that cause asynchronous grain filling will help to propose a model for how to regulate the rice inferior spikelets grain filling.

Results

In this study, two large panicle rice varieties, W1844 and CJ03, with the same sink capacity but with differences in asynchronous grain filling were used. The difference in the grain filling rate between superior and inferior spikelets in W1844 was much smaller than that in CJ03. We found that superior spikelet filling was initiated earlier in W1844 than in CJ03. The source-to-sink translocation rate of sucrose during the grain filling stage was more efficient in W1844 than in CJ03, and the gene expression levels of sucrose transporters (OsSUTs) were higher in W1844 functional leaves than in those of CJ03. In addition, carbon output, the transport ratio, and the contribution rate from the stem and sheath to the panicle were much higher at the early filling stage than at later filling stages in W1844.

Conclusion

Efficient sugar translocation can satisfy high sink strength, and also the strong sink activity can facilitate the sugar unloading in spikelets. All the above results indicate that an efficient sugar translocation rate at the early grain filling stage can improve sink strength and inferior grain filling initiation. Strategies to limit asynchronous grain filling in rice were also discussed based on our findings.

中文翻译：

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大穗水稻糖转运效率影响劣质灌浆的发生。

背景

大穗型水稻的库容较大，但由于灌浆不同步，该品种的小穗灌浆较差。了解导致籽粒灌浆不同步的因素将有助于提出如何调控水稻劣质小穗籽粒灌浆的模型。

结果

本研究使用两个大穗型水稻品种 W1844 和 CJ03，它们具有相同的库容量，但灌浆不同步的情况不同。W1844优劣穗灌浆率差异远小于CJ03。我们发现，W1844 中的小穗充盈期比 CJ03 更早。W1844灌浆期蔗糖源库易位效率高于CJ03，W1844功能叶中蔗糖转运蛋白（OsSUT）基因表达水平高于CJ03。此外，W1844灌浆前期的碳产量、输送率以及茎鞘对穗的贡献率均远高于灌浆后期。

结论

高效的糖转运可以满足高的库强度，而强的库活性有利于小穗中的糖卸载。上述结果表明，灌浆早期有效的糖转位速率可以提高库强度并改善灌浆启动不良。根据我们的研究结果，还讨论了限制水稻异步灌浆的策略。