Grain yield and yield attributes of newly developed low-cadmium rice varieties

Figures (3) Tables (5)

Figure 1.
Daily mean temperature (a) and solar radiation (b) during the rice-growing season (from transplanting to maturity) in 2024 and 2025.
Figure 2.
(a) Total biomass production, (b) source–sink ratio, and (c) harvest index of five rice varieties in 2024 and 2025. Columns and error bars represent the means and standard errors, respectively, across five nitrogen (N) application rates, with three replicates per N application rate (n = 15). Within each year, means sharing the same letters are not significantly different at the 0.05 probability level. ALY2, QLSM, QLXZ, XZ3, and NX42 refer to the newly developed low-cadmium (Cd) rice varieties Anliangyou 2, Qingliansimiao, Qinglianxiangzhan, and Xizi 3 and the widely grown non-low-Cd variety Nongxiang 42, respectively.
Figure 3.
(a) Total nitrogen (N) uptake and (b) internal N use efficiency of five rice varieties in 2024 and 2025. Columns and error bars represent the means and standard errors, respectively, across five N application rates, with three replicates per N application rate (n = 15). Within each year, means sharing the same letters are not significantly different at the 0.05 probability level. ALY2, QLSM, QLXZ, XZ3, and NX42 refer to the newly developed low-cadmium (Cd) rice varieties Anliangyou 2, Qingliansimiao, Qinglianxiangzhan, and Xizi 3 and the widely grown non-low-Cd variety Nongxiang 42, respectively.

Soil chemical property	Value
pH	6.61
Organic matter (g kg^–1)	28.7
Total N (g kg^–1)	2.19
Available N (mg kg^–1)	171
Total P (g kg^–1)	0.500
Available P (mg kg^–1)	9.28
Total K (g kg^–1)	17.2
Available K (mg kg^–1)	103
Total Cd (mg kg^–1)	0.366
Available Cd (mg kg^–1)	0.255
N, P, K, and Cd are nitrogen, phosphorus, potassium, and cadmium, respectively.

Table 1.

Soil chemical properties of the top 20 cm of the experimental field.

Variety^a	Type	Grain Cd content (mg kg⁻¹)^b	Parent^c		Release year
Variety^a	Type	Grain Cd content (mg kg⁻¹)^b	Female	Male	Release year
ALY2	Low-Cd	0.000−0.159	An 1S	Dige 2	2024
QLSM	Low-Cd	0.000−0.130	Huazhan/Guangchaosimiao	Dige 1	2024
QLXZ	Low-Cd	0.000−0.150	Dige 1	Xiangzhan	2024
XZ3	Low-Cd	0.000−0.098	Huanghuazhan	Luohong 4A/IR28	2023
NX42	Non-low-Cd	Not available	Xiangwanxian 17	Gumei 4	2020
^a ALY2, QLSM, QLXZ, XZ3, and NX42 refer to the rice varieties Anliangyou 2, Qingliansimiao, Qinglianxiangzhan, Xizi 3, and Nongxiang 42, respectively. ^b Data on grain Cd content were sourced from the China Rice Data Center (www.ricedata.cn/variety). For ALY2, QLSM, and QLXZ, the data were derived from analyses of brown rice samples obtained through regional trials, production trials, and pond cultivation identification experiments conducted in Hunan Province. In the pond cultivation identification experiments, soil pH ranged from 5.0 to 6.0, and two soil Cd contents were applied: 0.7 ± 0.1 and 1.5 ± 0.1 mg kg⁻¹. For XZ3, the data were obtained from analyses of brown rice samples collected in regional trials carried out in the middle and lower reaches of the Yangtze River. In China, the permissible limit for grain Cd content in rice is 0.2 mg kg⁻¹. ^c Dige 1, Dige 2, and Luohong 4A are low-Cd rice germplasms carrying OsNRAMP5 mutations.

Table 2.

Information on the four newly developed low-cadmium (Cd) rice varieties and the widely grown non-low-Cd rice variety used in this study.

Variable	F-value
Variable	2024	2025
Grain yield	1.40^NS	0.77^NS
Panicles m⁻²	0.82^NS	0.66^NS
Spikelets panicle⁻¹	1.74^NS	0.59^NS
Spikelets m⁻²	0.79^NS	0.74^NS
Spikelet filling percentage	2.76**	3.06**
Grain weight	0.92^NS	1.21^NS
Total biomass production	1.83^NS	0.35^NS
Harvest index	5.07**	1.52^NS
Sink capacity	0.81^NS	0.54^NS
Source–sink ratio	6.50**	1.39^NS
Total N uptake	1.04^NS	0.43^NS
Internal N use efficiency	0.80^NS	1.47^NS
** indicates significance at the 0.01 probability level, and ^NS indicates nonsignificance at the 0.05 probability level.

Table 3.

Analysis of variance of the interactive effects of variety and nitrogen application rate on yield formation characteristics in rice in 2024 and 2025.

	Experimental factor	Grain yield (t ha⁻¹)
	Experimental factor	2024	2025
Variety^a	ALY2	7.79 ± 0.37^a	8.01 ± 0.25^a
	QLSM	7.02 ± 0.25^b	7.72 ± 0.35^a
	QLXZ	6.62 ± 0.25^c	6.49 ± 0.26^b
	XZ3	6.52 ± 0.32^c	7.67 ± 0.33^a
	NX42	6.36 ± 0.21^c	6.89 ± 0.27^b
N application rate (kg ha⁻¹)	0	5.32 ± 0.12^d	5.94 ± 0.17^c
	90	6.18 ± 0.16^c	7.08 ± 0.24^b
	120	7.27 ± 0.22^b	7.48 ± 0.29^b
	150	7.82 ± 0.19^a	8.16 ± 0.35^a
	180	7.72 ± 0.21^a	8.12 ± 0.15^a
Data for each variety are presented as the mean ± standard error across five N application rates, with three replicates per N application rate (n = 15), and for each N application rate as mean ± standard error across five varieties, with three replicates per variety (n = 15). Within a column for each experimental factor (variety or N application rate), means sharing the same letters are not significantly different at the 0.05 probability level. ^a ALY2, QLSM, QLXZ, XZ3, and NX42 refer to the newly developed low-cadmium (Cd) rice varieties Anliangyou 2, Qingliansimiao, Qinglianxiangzhan, and Xizi 3 and the widely grown non-low-Cd variety Nongxiang 42, respectively.

Table 4.

Grain yield of five rice varieties grown under five nitrogen (N) application rates in 2024 and 2025.

	Variety^a	Panicles m⁻²	Spikelets panicle⁻¹	Spikelets m⁻² (×10³)	Spikelet filling (%)	Grain weight (mg)	Sink capacity (g m⁻²)
2024	ALY2	252 ± 10^b	176 ± 4^a	44.4 ± 1.9^a	76.4 ± 0.7^b	23.3 ± 0.1^b	1,033 ± 45^a
	QLSM	223 ± 10^cd	162 ± 4^c	36.1 ± 1.7^c	85.5 ± 0.8^a	23.0 ± 0.1^b	831 ± 37^d
	QLXZ	239 ± 8^bc	165 ± 4^bc	39.4 ± 1.6^b	73.4 ± 0.7^c	24.3 ± 0.2^a	958 ± 42^b
	XZ3	274 ± 11^a	173 ± 4^ab	47.4 ± 1.8^a	70.6 ± 1.6^d	20.0 ± 0.2^c	948 ± 34^bc
	NX42	211 ± 4^d	168 ± 4^abc	35.4 ± 1.3^c	78.0 ± 0.9^b	24.5 ± 0.1^a	868 ± 35^cd
2025	ALY2	274 ± 11^b	152 ± 2^a	41.6 ± 2.1^b	75.9 ± 0.9^bc	25.4 ± 0.1^c	1,058 ± 55^a
	QLSM	276 ± 13^b	133 ± 2^c	36.7 ± 1.7^c	81.4 ± 1.2^a	25.0 ± 0.1^d	918 ± 43^c
	QLXZ	264 ± 10^b	127 ± 3^c	33.5 ± 1.3^d	74.6 ± 1.6^c	26.8 ± 0.2^a	899 ± 37^c
	XZ3	295 ± 13^a	153 ± 1^a	45.1 ± 2.1^a	75.4 ± 1.1^bc	22.0 ± 0.1^e	993 ± 48^b
	NX42	260 ± 12^b	140 ± 3^b	36.4 ± 1.8^c	78.1 ± 2.0^b	26.0 ± 0.2^b	946 ± 48^bc
Data are presented as the mean ± standard error across five nitrogen (N) application rates, with three replicates per N application rate (n = 15). Within a column for each year, means sharing the same letters are not significantly different at the 0.05 probability level. ^aALY2, QLSM, QLXZ, XZ3, and NX42 refer to the newly developed low-cadmium (Cd) rice varieties Anliangyou 2, Qingliansimiao, Qinglianxiangzhan, and Xizi 3 and the widely grown non-low-Cd variety Nongxiang 42, respectively.

Table 5.

Yield components of five rice varieties in 2024 and 2025.