阐明谷子(Setaria italica var. germanica)杂种优势的生理机制是提高谷子杂交种产量的重要基础。2023-2024年, 以3个高产谷子杂交种长杂谷466、长杂谷2922和长杂谷333及其亲本为供试材料, 测定杂交种及其亲本的产量性状及生理指标, 对杂交种的产量优势及其影响因子进行系统分析, 初步解析了杂种优势的生理机制。结果表明, 在整个生育期内, 3个杂交种的叶绿素含量均高于双亲, 其中长杂谷466在拔节期的叶绿素含量最高, 达13.86 mg∙g^-1 FW。在苗期和拔节期, 3个杂交种的根系活力均显著高于双亲, 其中长杂谷466在苗期的根系活力最高, 为1.76 mg∙g^-1∙h^-1, 分别为其父母本的7.8倍和5.5倍; 长杂谷2922在苗期的根系活力较父母本分别高0.38和0.66 mg∙g^-1∙h^-1; 而长杂谷333在拔节期优势更为显著, 较父母本分别高0.31和0.62 mg∙g^-1∙h^-1。在产量形成性状方面, 与双亲相比, 杂交种的灌浆速率和颖花数均显著提高, 长杂谷466在花后19天灌浆速率达最大值, 为1.58 g∙d^-1 per panicle; 长杂谷466和长杂谷333颖花数极显著高于其亲本, 长杂谷2922颖花数显著增加。此外, 杂交种根系的氮素积累量和氮素转运效率也表现出一定的优势, 其中长杂谷2922根系氮素积累优势最大且氮素转运效率(近56%)最高, 显著高于其父本M22。综上表明, 长杂谷系列杂交种通过提高光合能力、养分吸收利用效率、籽粒灌浆速率和颖花数实现产量增加。

INTRODUCTION: In agricultural production, the utilization of heterosis has brought significant benefits to society and economic development by markedly increasing crop yield, stress resistance, and quality. Foxtail millet (Setaria italica var. germanica), as an important coarse grain crop in the arid and semi-arid regions of northern China, holds a significant position in dry land ecological agriculture. However, the slow increase in the yield of foxtail millet has limited the further realization of its production potential. Utilizing heterosis has thus become one of the effective ways to increase the yield of foxtail millet. Nevertheless, research on the physiological and molecular mechanisms of its heterosis is still relatively weak, and the mechanism remains unclear. Therefore, to understand the physiological mechanisms of heterosis in foxtail millet is of great importance for improving the yield of hybrid varieties.
RATIONALE: The Changzagu series of foxtail millet hybrids (Changzagu466, Changzagu2922, and Changzagu333) exhibit significant heterosis in yield. In order to elucidate its mechanism, we systematically analyzed the yield advantages of these hybrids and their influencing factors by measuring yield-related traits and key physiological indicators of the hybrids and their parental lines.
RESULTS: Throughout the entire growth period, the chlorophyll content of the three hybrid varieties was higher than that of their parents. Among them, Changzagu466 exhibited the highest chlorophyll content at the jointing stage, reaching 13.86 mg∙g^-1 FW. During the seedling and jointing stages, the root activity of the three hybrids was significantly higher than that of their parents. Specifically, Changzagu466 showed the highest root activity at the seedling stage, measuring 1.76 mg∙g^-1∙h^-1, which was 7.8 times and 5.5 times higher than its female and male parents, respectively. The root activity values of Changzagu2922 at the seedling stage were 0.38 and 0.66 mg∙g^-1∙h^-1 higher than its female and male parents, respectively. Meanwhile, Changzagu333 displayed pronounced advantages at the jointing stage, with root activity values 0.31 and 0.62 mg∙g^-1∙h^-1 higher than its female and male parents, respectively. In terms of yield-related traits, compared to their parents, the hybrids showed significant improvements in both grain filling rate and spikelet number. Changzagu466 reached its maximum grain filling rate of 1.58 g∙d^-1 per panicle at 19 days after flowering. Both Changzagu466 and Changzagu333 had significantly higher spikelet numbers than their parents, while Changzagu2922 also showed a significant increase in spikelet numbers. In addition, the hybrid varieties also demonstrate certain advantages in root nitrogen accumulation and nitrogen translocation efficiency. Among them, Changzagu2922 exhibits the strongest root nitrogen accumulation advantage and the highest nitrogen translocation efficiency (nearly 56%), both are significantly higher than that of its male parent line M22.
CONCLUSION: The Changzagu series of foxtail millet hybrids effectively enhances photosynthetic capacity, nutrient absorption and utilization efficiency by significantly increasing chlorophyll content, root activity during the early growth stages, and root nitrogen accumulation. Meanwhile, the significant increase in grain filling rate and spikelet number of the hybrids further enhances both grain weight and grain number per panicle, ultimately achieving high yield.

Foxtail millet and parental trait comparison chart