Heterosis in Yield and Its Physiological Mechanism of Changzagu Series Millet Hybrids

doi:10.11983/CBB24187

Abstract

Abstract: 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

Key words: hybrid millet, physiological index, grain filling rate, agronomic traits, yield

Yurong Guo, Hong Liu, Zhenhua Wang, Gang Tian, Xin Liu, Jie Guo, Chunyong Li, Huixia Li. Heterosis in Yield and Its Physiological Mechanism of Changzagu Series Millet Hybrids[J]. Chinese Bulletin of Botany, 2025, 60(6): 931-943.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB24187

https://www.chinbullbotany.com/EN/Y2025/V60/I6/931

Figures/Tables 10

Figure 1 Chlorophyll content of millet at different growth stages The materials Changzagu466, its paternal parent is K34 and its maternal parent is Gu3A; Changzagu2922, its paternal parent is M22 and its maternal parent is Jin29A; Changzagu333, its paternal parent is K410 and its maternal parent is Gao51A. Different lowercase letters indicate significant differences at the 0.05 level.

Figure 2 Root activity of millet at different growth stages The materials are the same as shown in Figure 1. Different lowercase letters indicate significant differences at the 0.05 level.

Figure 3 Heterosis in physiological index of millet RA: Root activity; Chl: Chlorophyll content; S: Seedling stage; J: Jointing stage; FH: Full heading stage; G: Grouting stage; H: Over-parent advantage; L: Low-parent advantage; M: Medium-parent advantage. The scale color indicates the dominance range (-100-100); red represents the positive dominance level and blue represents the negative dominance level, and the dominance color beyond the range is indicated by the deepest color.

Figure 4 Dynamic of grain dry matter accumulation of millet in grouting stage

Table 1 Over-parent advantage of dry matter accumulation of millet in different grouting stages

Variety	Dry matter accumulation (g∙d^-1 per panicle)			Over-parent heterosis (%)
Variety	0-t1	t1-t2	t2-t3	0-t1	t1-t2	t2-t3
Changzagu466	0.53	1.39	0.39	63	28	29
K34	0.32	1.09	0.31	63	28	29
Changzagu2922	0.43	1.09	0.30	27	44	38
M22	0.34	0.76	0.21	27	44	38
Changzagu333	0.49	1.20	0.33	30	36	79
K410	0.38	0.88	0.25	30	36	79

Figure 5 Nitrogen accumulation and nitrogen translocation efficiency in different organs of millet at different growth stages (A) Nitrogen accumulation at seedling stage; (B) Nitrogen accumulation at jointing stage; (C) Nitrogen accumulation at full heading stage; (D) Nitrogen accumulation at grouting stage; (E) Nitrogen accumulation at maturity stage; (F) Nitrogen transport efficiency. Different lowercase letters indicate significant differences at the 0.05 level.

Table 2 Analysis of yield-related agronomic traits of millet

Figure 6 Heterosis in agronomic traits of millet The abbreviations of traits are the same as shown in Table 2. H: Over-parent advantage; L: Low-parent advantage; M: Medium-parent advantage. The scale color indicates the dominance range (-100-100); red represents the positive dominance level and blue represents the negative dominance level, and the dominance color beyond the range is indicated by the deepest color.

Table 3 Yield and yieid components of dfent milet vanetes

Table 4 Yield and yield component factors for over-parent advantage in millet

Traits	Changzagu- 466	Changzagu- 2922	Changzagu- 333
PW (%)	37	28	61
TGW (%)	1	6	2
GWPP (%)	28	39	65
GP (%)	27	31	61
SP (%)	35	30	44
SSR (%)	-6	3	11
PY (%)	20	15	50

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