Background

The yield potential of super hybrid rice has been increased by nearly 10% compared to ordinary hybrid or inbred rice. To further explain the reasons for the yield advantage of hybrids, we conducted investigations into the underlying physiological mechanism by considering leaf photosynthesis in combination with assimilate translocation.

Methods

Field experiments were conducted from 2020 to 2021 to compare the yield, photosynthetic performance, and efficiency of assimilate translocation-related traits between super hybrid rice (Yliangyou5867 and Yliangyou3218) and inbred super rice (Zhendao11 and Nanjing9108) under two nitrogen (N) levels.

Results

The average yield of hybrids across N levels was respectively 15.7% and 25.3% higher than that of inbreds in 2020 and 2021. Before heading, the biomass of hybrids was significantly higher than that of inbreds, and hybrids exhibited a higher harvest index. The higher radiation use efficiency (RUE) in hybrids was primarily due to an improved photosynthetic rate (P_n). Dry matter translocation from stem and leaf to panicle of hybrids was higher than that of inbreds. The hybrids also exhibited greater fluctuation in day-night sugar content and higher phloem sugar content which indicated higher assimilate translocation efficiency with hybrids.

Conclusions

Our results revealed that the higher RUE was responsible for the higher aboveground biomass before heading in hybrids. Furthermore, the improved biomass partitioning and remobilization, as demonstrated by an increase in assimilate translocation efficiency, contributed to higher harvest index and grain yield in hybrids. Crop breeders should focus on coordinating light utilization and assimilate translocation efficiency in super hybrid rice.

中文翻译：

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更高的光利用率和同化转运效率提高了超级杂交稻的产量

背景

与普通杂交或自交稻相比，超级杂交稻的产量潜力提高了近10%。为了进一步解释杂交种产量优势的原因，我们通过结合叶片光合作用和同化物易位来研究其潜在的生理机制。

方法

2020年至2021年进行了田间试验，比较了两个氮（N）水平下超级杂交稻（Y两优5867和Y良优3218）和自交超级稻（珍稻11和南京9108）的产量、光合性能和同化易位相关性状效率。

结果

2020年和2021年，杂交种跨氮水平平均产量分别比自交系高15.7%和25.3%。抽穗前，杂交种生物量显着高于自交系，收获指数更高。杂交种较高的辐射利用效率（RUE）主要是由于光合速率（P _n）的提高。杂种的干物质从茎叶向穗部的转移高于自交系。杂种还表现出较大的昼夜糖含量波动和较高的韧皮部糖含量，这表明杂种的同化易位效率较高。

结论

我们的结果表明，较高的 RUE 是造成杂种抽穗前较高地上生物量的原因。此外，同化物易位效率的提高证明了生物量分配和再利用的改善，有助于提高杂交种的收获指数和谷物产量。作物育种者应重点协调超级杂交稻的光利用和同化易位效率。