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Article

Changes in Rice Yield and Quality from 1994 to 2023 in Shanghai, China

by
Haixia Wang
1,2,
Jianjiang Bai
1,
Qi Zhao
1,
Jianhao Tang
1,
Ruifang Yang
1,
Liming Cao
1 and
Ruoyu Xiong
1,*
1
Key Laboratory of Germplasm Innovation and Genetic Improvement of Grain and Oil Crops, Co-Construction by Ministry and Province, Ministry of Agriculture and Rural Affairs, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China
2
Agricultural Technology Extension Center of Zhucheng City, Weifang 261000, China
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(3), 670; https://doi.org/10.3390/agronomy15030670
Submission received: 13 February 2025 / Revised: 1 March 2025 / Accepted: 7 March 2025 / Published: 8 March 2025
(This article belongs to the Section Farming Sustainability)
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Abstract

:
In recent years, there has been widespread cultivation of high-quality rice along the southeast coast of China, particularly in Shanghai. However, the specific changes in the yield and quality performance of rice in the Shanghai region have not been well understood. A study conducted on 194 rice varieties in the Shanghai region from 1994 to 2023 focused on yield, growth characteristics, and quality. The findings revealed significant increases in rice yield (+16.8%) and spikelets per panicle (+45.4%) in the Shanghai region over the past 30 years, along with a decrease in amylose content (−27.9%). However, parameters such as grain filling, 1000-grain weight, plant height, panicle length, chalkiness, and gel consistency showed no significant changes over the same period. Additionally, the study found that the yield, nitrogen application amount, growth period, and head rice rate of japonica rice and indica-japonica hybrid rice were higher than those of indica rice, although the panicle length was lower in comparison. Japonica inbred rice exhibited the lowest amylose content and superior taste. Correlation analyses suggested that the breeding of japonica rice varieties in the Shanghai region should focus on balancing nitrogen absorption and high chalkiness, plant biomass, and amylose content, and yield and the appearance and taste quality of rice. In addition, the potential rice yield per unit area in the Shanghai region in the future depends on the promotion of hybrid japonica rice planting and developing best management practices.

1. Introduction

Rice production accounts for approximately one-third of grain production in China, playing a crucial role in ensuring national food security [1]. The yield per unit area of rice has significantly increased from 1.97 t ha−1 in 1949 to 7.20 t ha−1 in 2014, representing a 3.66 time increase in yield levels [2]. This surge in rice yield in China can be attributed to the effective utilization of variety yield potential and advancements in cultivation techniques [3]. For example, GNA transcription factors were found to promote the accumulation of cytokinin in the panicle by inhibiting the production of cytokinin oxidoreductase, thereby increasing the rice yield [4]. Deleting a 54-base pair cis-regulatory region in IPA1 using CRISPR-Cas9 technology can significantly increase the rice yield [5]. Nowadays, as living standards have improved, there has been growing emphasis on rice quality, encompassing processing, appearance, cooking and eating, and nutrition quality [6]. Therefore, a large number of studies have clarified the regulatory effects of the ALK, GS3, Wx, OsGRF8, and POW1 genes on rice appearance and cooking and eating quality [7,8,9]. In recent years, there has been a notable acceleration in the renewal rate of rice varieties, continuous enhancements in quality breeding, and expansion of the area planted with superior rice varieties [10]. These developments have significantly contributed to the transformation and modernization of China’s rice industry.
The quality improvement of new rice varieties is crucial for achieving high-quality rice production. Varieties of japonica rice and indica rice have different quality parameters; these differences are mainly reflected in appearance and eating and nutritional quality. In the southern double-cropping rice region, Zeng et al. [11] observed that the quality of indica rice improved more than that of japonica rice. However, the stickiness of japonica rice is higher, especially for soft rice, which is more favored by consumers living along the southeast coast [12]. Inbred rice generally exhibits higher quality compared to hybrid rice, particularly three-line hybrid indica rice and japonica rice [13]. It may be that hybrid rice prioritizes the improvement of yield and neglects the simultaneous improvement of quality in the breeding process [11]. Japonica rice is typically grown in the northeast and southeast coastal regions of China, while indica rice is predominantly cultivated in the southern double-cropping area [14]. The Shanghai region, being the most developed coastal area in the country, has high demand for japonica rice. This prompted breeders to pay more attention to the improvement of japonica rice taste and appearance quality. However, the availability of cytoplasmic resources for sterile japonica rice lines is limited, resulting in less significant heterosis [15]. Moreover, the quality of rice varieties can vary significantly from year to year, lacking stability, which poses a major challenge in achieving consistent quality in rice production [16].
The continuous breeding of new varieties with high yield and high quality is undeniably the most effective and cost-efficient method to enhance the yield and quality of rice. Understanding the underlying principles governing the development of high-yield and high-quality rice varieties is a crucial objective in cultivation research. We hypothesize that there are differences in rice yield and quality traits from the past 30 years in the Shanghai region. Therefore, we aimed to (1) analyze the yield and quality trends of 194 rice types in the Shanghai region from 1994 to 2023; (2) investigate the variations in yield and quality across different rice varieties types in the past 30 years; and (3) propose future strategies for enhancing rice yield and quality in the Shanghai region.

2. Materials and Methods

2.1. Data Collection of Shanghai Region State-Certified Rice Varieties from 1994 to 2023

From 1994 to 2023, a study was conducted to analyze the yield, nitrogen fertilizer application, growth characteristics, and quality traits of 194 rice varieties in the Shanghai region. These traits were evaluated and approved by the Provincial Crop Variety Evaluation Committee (PCVAC) of the China Rice Data Center (www.ricedata.cn). The released rice varieties included glutinous rice, water-saving and drought-resistant rice, high resistant starch rice, blast resistant rice, and stripe blight resistant rice, excluding sterile lines. Based on subspecies (japonica rice, indica rice) and breeding types (hybrid, inbred), the varieties were categorized into 127 japonica inbred rice, 48 japonica inbred rice, five indica inbred rice, nine indica inbred rice, and five indica-japonica hybrid rice varieties.

2.2. Rice Yield, Growth Characteristics, and Quality Trait Description

The collected data on yield, nitrogen fertilizer application, growth characteristics, and quality traits included parameters such as effective panicle, spikelets per panicle, grain filling, 1000-grain weight, yield, nitrogen fertilizer amounts, growth period, plant height, panicle length, head rice rate, chalky rate, chalky degree, gel consistency, and amylose content. These characteristics were determined by the Inspection and Testing Center of Rice and Product Quality Supervision General Group of the Ministry of Agriculture, following the method outlined by Peng et al. [17]. The yield was determined by harvesting 667 m2 of rice with a water content equivalent to 13.5%. The effective panicle was calculated by measuring the panicle number of 5 m2 of rice. For determining the number of effective panicles, five stump rice plants were taken to measure the total number of grains, the number of empty grains, the spikelets per panicle, the grain filling, and the 1000-grain weight. Then, 120 g rice samples were husked by a brown rice machine and milled rice machine to remove the aleux layer, and the broken rice was screened to produce head rice. The ratio of the head rice weight to the 120 g rice sample was the head rice rate. We then selected 100 grains of head rice, and for the white belly, white middle, and white back area, more than 20% was chalky grain, and the chalky rate was the percentage of chalky grain and whole head rice samples. Ten chalky grains were randomly selected, and the chalky degree was the proportion of the chalky area to the total area. We ground the milled rice into flour through a 100-mesh sieve, accurately weighing 100 mg rice flour, added 0.2 mL thymol blue solution and 2 mL 0.2 mol/L KOH solution, and heated, cooled, and measured the length of the rice glue, that is, the gel consistency. The amylose content of the rice was determined via a spectrophotometer (Shanghai Yoke Instrument Co., Ltd., Shanghai, China) at 620 nm through iodine colorimetry.

2.3. Statistical Analysis

The mean yield, growth characteristics, and quality traits along with their variation coefficients were analyzed using SPSS 22.0 statistical software (SPSS Inc., Chicago, IL, USA) to determine the least significant difference (LSD) at a significance level of p < 0.05. The variation coefficient for each yield, growth characteristic, and quality trait was calculated as the ratio of the standard deviation to the average value of the respective trait. Pearson’s correlation analysis was employed to investigate the relationships among yield, growth characteristics, and quality traits at a significance level of 0.05. According to Xie et al. [18], the GEEBiplotGUI package in R language (Version 4.2.2) was used to implement the biplot of multivariate stability.

3. Results

3.1. Variation Characteristics of Rice Yield from 1994 to 2023

From 1994 to 2023, rice yield exhibited a generally increasing trend, reaching its peak at 9.7 t ha−1 (2014–2018) in the Shanghai region (Figure 1A). Compared to 1994–1998, the maximum yield increased significantly by 16.8%. The variation in yield was primarily attributed to changes in the effective panicle and the spikelets per panicle, rather than the grain filling or 1000-grain weight (Figure 1B–E). Over time, the number of effective panicles decreased significantly, a 19.1% decrease at most compared with 1994–1998. Conversely, the spikelets per panicle showed a significant increase, with a maximum increase of 45.4% when compared to 1994–1998. Notably, there was no significant difference in nitrogen application amounts across the years. The growth characteristics of rice, including growth period, plant height, and panicle length, remained relatively stable over the past three decades, except for a significant decrease in the growth period observed from 2004 to 2008 (Figure 2).

3.2. Variation Characteristics of Rice Quality from 1994 to 2023

The head rice rate from 2004 to 2008 was significantly lower than in other years (Figure 3A). However, the chalky rate, chalky degree, and gel consistency showed no significant differences across the years (Figure 3B–D). In comparison to the amylose content recorded from 1994 to 1998, a significant decrease of 27.9% was observed during the period from 2019 to 2023 (Figure 3E).

3.3. Changes in Rice Yield Between Different Variety Types in Past 30 Years

Indica hybrid rice had the lowest yield in the Shanghai region over the past 30 years (Figure 4A). Compared to indica hybrid rice, the yield of indica inbred rice, japonica inbred rice, japonica hybrid rice, and indica-japonica hybrid rice were higher by 2.3%, 2.4%, 12.3%, and 33.9%, respectively (Figure 4A). Yield composition indicates that inbred rice exhibited a higher effective panicle, while hybrid rice, particularly indica-japonica hybrid rice, had the lowest effective panicle (Figure 4B). The spikelets per panicle were the lowest for japonica inbred rice and the highest for indica-japonica hybrid rice (Figure 4C), while the grain filling showed the opposite trend (Figure 4D). Indica inbred rice had the lowest 1000-grain weight, followed by indica-japonica hybrid rice (Figure 4E). Indica hybrid rice, japonica hybrid rice, and japonica inbred rice had higher 1000-grain weights.
The nitrogen application amounts and growth periods of japonica and indica-japonica hybrid rice were significantly higher than those of indica (Figure 4F and Figure 5A). Conversely, panicle length showed the opposite trend, with japonica inbred rice being the lowest (Figure 5B). The plant height of hybrid rice was greater than that of inbred rice, with the plant height of japonica inbred rice being the lowest (Figure 5B,C).

3.4. Changes in Rice Quality Between Different Variety Types in Past 30 Years

The head rice rates of japonica rice and indica-japonica hybrid rice were significantly higher than that of indica rice, while the rate of indica inbred rice was significantly higher than that of indica hybrid rice (Figure 6A). When analyzing the appearance quality of the rice, there was no significant difference in chalky rate and chalky degree among the types of rice varieties (Figure 6B,C). Cooking and eating quality results showed that, compared to indica inbred rice, the gel consistency of indica-japonica hybrid rice increased significantly by 13.0% (Figure 6D). The amylose content of japonica inbred rice was the lowest, being significantly lower than those of indica hybrid rice and japonica hybrid rice (Figure 6E).

3.5. Correlation Analysis of Rice Yield and Quality in Past 30 Years

Correlation analysis revealed a significant positive relationship between nitrogen application amounts with growth period, yield, grain filling, head rice rate, and chalky rate (Figure 7). Conversely, there was a significant negative correlation with effective panicle.
The correlation analysis revealed that the growth period, plant height, and panicle length had a negative correlation with the effective panicles, but a positive correlation with the spikelets per panicle. Additionally, there was a significant positive correlation among the growth period and yield, 1000-grain weight, and head rice rate. Plant height and panicle length were positively correlated with amylose content and negatively correlated with grain filling. Furthermore, plant height showed a significant positive correlation with yield, while panicle length exhibited a significant negative correlation with the head rice rate.
Correlation analysis revealed a positive relationship between yield and spikelets per panicle with chalky rate, chalky degree, and amylose content. Conversely, effective panicle and seed grain filling exhibited an inverse correlation. Moreover, yield, grain filling, and 1000-grain weight were found to be significantly positively associated with the head rice rate. Additionally, a significant positive correlation was observed between the 1000-grain weight and chalky rate.

3.6. Stability of Different Types of Rice Varieties

In 30 years, japonica inbred rice showed the highest yielding ability, followed by japonica hybrid rice, indica rice, and indica-japonica hybrid rice. Similarly, japonica hybrid rice showed the highest stability, followed by indica-japonica hybrid rice, and the stability of japonica hybrid rice was poor (Figure 8A). In addition to japonica inbred rice, other types of rice had the worst stability in 2019–2023 (Figure 8B–F).

4. Discussion

4.1. Temporal Changes in Rice in Shanghai Region

In recent years, as living standards have improved, the collaborative enhancement of rice yield and quality has become a pressing issue that requires thorough investigation and resolution [6]. Analysis of the rice varieties cultivated in the Shanghai region over the past three decades reveals a notable increase in rice yield and a corresponding decrease in amylose content (Figure 1 and Figure 3). This trend underscores the emphasis placed on enhancing both yield and cooking and eating quality (CEQ) in rice (especially inbred japonica soft rice) breeding efforts in the Shanghai region. The increase in rice yield can be attributed to a significant increase in the number of spikelets per panicle, despite a decrease in effective panicles (Figure 1). This trend may be a result of optimizing rice population, reducing ineffective tillering, and enhancing the establishment of a photosynthetic population [19,20,21]. Additionally, the increase in sink source could play a role in boosting yield [22,23]. The grain filling, 1000-grain weight, and growth characteristics of rice varieties in the Shanghai region have not shown significant improvement over the past 30 years (Figure 1 and Figure 2). This suggests that focusing on enhancing these aspects could be a key direction for increasing rice yield in the region. Furthermore, data from 1994 to 2023 reveal that the nitrogen fertilizer application amounts for rice have been consistently around 300 kg ha−1, indicating that there is untapped potential for more efficient nitrogen absorption in rice plants (Figure 1). The appropriate application of nitrogen fertilizer can promote the growth and development of rice, enhance photosynthetic efficiency, and increase effective panicles, spikelets per panicle, and 1000-grain weight, thereby significantly improving rice yield [24]. However, increased nitrogen application does not always lead to better outcomes. Research indicates that when nitrogen application exceeds a certain threshold, the increase in rice yield gradually diminishes and may even decline [25]. The optimal yield increase is achieved when the nitrogen proportion in basal and tillering fertilizers represents less than 70% of the total nitrogen application, and the proportion of panicle fertilizer is 10–30% [26]. In recent years, global warming has resulted in significant inter-annual fluctuations in rice yields. High temperature stress adversely affects rice photosynthesis, grain filling, and material transport, ultimately leading to reduced yields [27]. Our research findings further indicate that japonica hybrid rice, indica rice, and indica-japonica hybrid rice exhibited poor yield stability from 2019 to 2023 (Figure 8). Consequently, in the context of global warming, the safety concerns surrounding Shanghai’s rice yield industry must not be overlooked.
Consumers typically prioritize the processing quality, appearance quality, and taste quality of rice [28]. Over the past three decades, there has been a significant decrease in amylose content. It is generally understood that rice with low amylose content offers better taste [29], making the breeding of high-CEQ rice in Shanghai region more successful. Previous research has identified numerous QTL (Quantitative Trait Locus) associated with processing quality in rice, including qBR-1, qMR-6, qMR-8, qHR-1, qHR-3, and qHR-6 [30,31]. However, the stable expression and precise localization of these QTL remain a challenge [32]. Rice chalkiness, characterized by an opaque endosperm phenotype, is attributed to the loose and irregular arrangement of starch grains. Various studies have explored the genetic factors underlying rice chalkiness, such as Chalk5, flo2, flo5, flo8, flo10, flo11, flo19, and gwc1 [33,34,35,36]. Future advancements in rice quality breeding could focus on enhancing rice milling yield, reducing chalkiness, and improving gel consistency. It is worth mentioning that in the past 30 years, there has been no significant difference in the rice quality traits (except amylose content). This is because these traits are co-regulated by multiple genes or the overapplication of nitrogen fertilizer offsets the improvement of rice quality traits [37,38].

4.2. Differences in Rice Types Traits in Shanghai Region

Significant variations in yield, growth characteristics, and quality were observed among different rice varieties in the Shanghai region over 30 years (Figure 4, Figure 5 and Figure 6). Indica-japonica hybrid rice exhibited the highest yield potential, followed by japonica rice and indica rice (Figure 4). The utilization of crop heterosis is an important way to greatly increase grain yield. Generally, the more distant the relationship between varieties, the more obvious the hybridization [39]. Our study showed that the high yield of indica-japonica hybrid rice was due to higher spikelets per panicle but lower effective panicles and 1000-grain weight in the Shanghai region (Figure 4). Zheyou 915 indica-japonica hybrid rice can significantly increase yield by increasing the 1000-grain weight [40]. This indicates that other yield components are also breakthrough points for the yield of indica-japonica hybrid rice. The lower yield of indica rice could potentially be attributed to this type’s water-saving and drought-resistant nature (Table S1). Japonica rice emerged as the predominant and most stable type of rice in the Shanghai region, constituting 90.2% of all approved rice varieties over the past three decades (Figure S1 and Figure 8). The rice planting area in the Shanghai region for 2023 is approximately 88,000 hectares, all dedicated to japonica rice. This includes 31,000 hectares of hybrid japonica rice and 57,000 hectares of inbred japonica rice. Hybrid japonica rice is primarily cultivated for yield, whereas inbred japonica rice is emphasized for its quality. Indeed, our results indicated that hybrid rice had a lower effective panicle compared to inbred rice, however, it had higher spikelets per panicle (Figure 4). The aim of achieving a super high yield of rice typically involves maintaining a reasonable rice population, along with high effective panicles, spikelets per panicle, and 1000-grain weight [41,42]. In the case of japonica inbred rice in the Shanghai region, the breeding objective should focus on increasing the spikelets per panicle, as the effective panicle and grain filling are already high. Compared to japonica inbred rice, japonica hybrid rice exhibits relatively low effective panicles and grain filling, but with significant potential for improvement. Optimal temperature, light exposure, and fertilizer management are crucial factors that can further enhance the yield of japonica hybrid rice [43,44]. Moreover, it is important to note that the nitrogen fertilizer application rate for japonica rice and indica-japonica hybrid rice is considerably higher than that for indica rice, highlighting the need to address environmental concerns related to excessive fertilization.
Correlation analysis revealed that while increasing nitrogen fertilizer application can boost rice yield and the head rice rate, it also leads to an increase in chalkiness (Figure 7). Therefore, it is imperative to investigate methods to enhance efficient nitrogen absorption and reduce chalkiness in japonica rice cultivated in the Shanghai region. Grain grouting is the key period of chalkiness formation [45]. Previous research showed that nitrogen panicle fertilizer could prolong active filling duration, promote grain filling, increase dry matter accumulation, and reduce chalkiness [46]. It is an effective method to reduce chalkiness by optimizing the nitrogen application amount and the fertilization period [47]. A longer growth period, increased plant height, and longer panicle length in rice result in fewer effective panicles and higher amylose content (Figure 7). It is essential to delve deeper into the physiological aspects of rice in the Shanghai region, considering factors such as temperature, light availability, tillering, and source–sink dynamics. In addition, our study found that planting japonica rice in high-yield and high-efficiency cultivation mode would increase the yield per unit of rice by 5.3–33.5% compared with the average rice yield in the Shanghai region, especially for japonica hybrid rice (Figure S2). Therefore, hybrid japonica rice and its high-yield cultivation management had great potential to increase yield per unit area in the Shanghai region.
The planting system in the Shanghai region primarily focuses on single-season rice, utilizing the annual temperature and light resources effectively for japonica rice and indica-japonica hybrid rice due to their longer growth periods (Figure 5). Japonica rice typically has a lower plant height and panicle length, thus showing relatively good resistance to lodging [48]. Research findings indicate that both japonica rice and indica-japonica hybrid rice have significantly higher head rice rates compared to indica rice (Figure 6). Japonica inbred rice has the lowest amylose content, suggesting that japonica inbred rice demonstrates superior yield, lodging resistance, and quality in the Shanghai region, making it suitable for widespread adoption. Future efforts in the quality breeding of japonica hybrid rice could focus on reducing amylose content. Moreover, the presence of chalkiness and higher amylose content in rice is associated with increased yield and spikelets per panicle (Figure 7). This may be a contradiction between production and quality coordination. The significant discrepancy between rice yield and quality poses a critical challenge that requires attention and resolution in the future.

5. Conclusions

Over the past 30 years, there have been significant increases in rice yield and spikelets per panicle in the Shanghai region, accompanied by a decrease in amylose content and effective panicle. Notable stability was observed in grain filling, 1000-grain weight, nitrogen application amounts, plant height, panicle length, chalkiness, and gel consistency. The yield of indica-japonica hybrid rice surpassed those of japonica and indica rice. Inbred rice exhibited a higher effective panicle than hybrid rice. Japonica and indica-japonica hybrid rice showed significantly higher nitrogen application rates, growth periods, and head rice rates, while having shorter panicle lengths. Japonica inbred rice displayed the lowest amylose content and the best taste. Moving forward, it is imperative to focus on enhancing nitrogen efficiency and incorporating low chalkiness genes in the development of japonica rice in the Shanghai region. Efforts should also be directed towards mitigating the complex interplay among nitrogen application, plant biomass, amylose content, yield, and quality through improved cultivation techniques.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy15030670/s1, Figure S1: The breeding types of japonica rice at the past 30 years in Shanghai; Figure S2: Rice yield per unit area in Shanghai from 2018 to 2024, and average yield per unit area of inbred and hybrid japonica rice in high-yield and high-efficiency cultivation test sites (A). Average yield per unit of Shenyou (SY), Huayou 14 (HY 14) and Qiuyoujinfeng (QYJF) hybrid japonica rice cultivars from 2018 to 2024 (B); Table S1: Indica rice breeding types at the past 30 years in Shanghai.

Author Contributions

Writing—original draft preparation, H.W.; data curation, Q.Z. and J.T.; project administration, R.Y. and L.C.; writing—reviewing and editing, J.B. and R.X. All authors have read and agreed to the published version of the manuscript.

Funding

The study was funded by the Agriculture Research System of Shanghai, China (Grant No. 202403), and the Shanghai Agricultural Science and Technology Innovation Program (Grant No. T2024316).

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors upon request.

Acknowledgments

Thanks to all authors for their contributions and also to the Provincial Crop Variety Evaluation Committee (PCVAC) of China Rice Data Center (www.ricedata.cn).

Conflicts of Interest

The authors have declared no conflicts of interest.

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Figure 1. Changes in rice yield (A), yield composition (B–E), and nitrogen fertilizer application (F) in Shanghai region from 1994 to 2023. Different lowercase letters between different years are significant at p < 0.05.
Figure 1. Changes in rice yield (A), yield composition (B–E), and nitrogen fertilizer application (F) in Shanghai region from 1994 to 2023. Different lowercase letters between different years are significant at p < 0.05.
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Figure 2. Changes in rice growth period (A), plant height (B), and panicle length (C) in Shanghai region from 1994 to 2023. Different lowercase letters between different years are significant at p < 0.05.
Figure 2. Changes in rice growth period (A), plant height (B), and panicle length (C) in Shanghai region from 1994 to 2023. Different lowercase letters between different years are significant at p < 0.05.
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Figure 3. Changes in rice head rice rate (A), chalky rate (B), chalky degree (C), gel consistency (D), and amylose content (E) in Shanghai region from 1994 to 2023. Different lowercase letters between different years are significant at p < 0.05.
Figure 3. Changes in rice head rice rate (A), chalky rate (B), chalky degree (C), gel consistency (D), and amylose content (E) in Shanghai region from 1994 to 2023. Different lowercase letters between different years are significant at p < 0.05.
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Figure 4. Changes in rice yield (A), yield composition (B–E), and nitrogen fertilizer application (F) under different rice varieties in Shanghai region from 1994 to 2023. Different lowercase letters between different varieties are significant at p < 0.05.
Figure 4. Changes in rice yield (A), yield composition (B–E), and nitrogen fertilizer application (F) under different rice varieties in Shanghai region from 1994 to 2023. Different lowercase letters between different varieties are significant at p < 0.05.
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Figure 5. Changes in rice growth period (A), plant height (B), and panicle length (C) under different rice varieties in Shanghai region from 1994 to 2023. Different lowercase letters between different varieties are significant at p < 0.05.
Figure 5. Changes in rice growth period (A), plant height (B), and panicle length (C) under different rice varieties in Shanghai region from 1994 to 2023. Different lowercase letters between different varieties are significant at p < 0.05.
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Figure 6. Changes in rice head rice rate (A), chalky rate (B), chalky degree (C), gel consistency (D), and amylose content (E) under different rice varieties in Shanghai region from 1994 to 2023. Different lowercase letters between different varieties are significant at p < 0.05.
Figure 6. Changes in rice head rice rate (A), chalky rate (B), chalky degree (C), gel consistency (D), and amylose content (E) under different rice varieties in Shanghai region from 1994 to 2023. Different lowercase letters between different varieties are significant at p < 0.05.
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Figure 7. Correlation analysis of yield and yield composition, nitrogen application amounts, growth characteristics, and rice quality in Shanghai region from 1994 to 2023. GP, growth period; PH, plant height; PL, panicle length; EP, effective panicle; SPP, spikelets per panicle; GF, grain filling; GW, 1000-grain weight; NAA, nitrogen application amounts; HRR, head rice rate; CR, chalky rate; CD, chalky degree; GC, gel consistency; AC, amylose content. * indicates significant difference at p < 0.05.
Figure 7. Correlation analysis of yield and yield composition, nitrogen application amounts, growth characteristics, and rice quality in Shanghai region from 1994 to 2023. GP, growth period; PH, plant height; PL, panicle length; EP, effective panicle; SPP, spikelets per panicle; GF, grain filling; GW, 1000-grain weight; NAA, nitrogen application amounts; HRR, head rice rate; CR, chalky rate; CD, chalky degree; GC, gel consistency; AC, amylose content. * indicates significant difference at p < 0.05.
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Figure 8. Yield stability analysis of different varieties (A), and yield stability of indica inbred rice (B), indica hybrid rice (C), japonica inbred rice (D), japonica hybrid rice (E), and indica-japonica hybrid rice (F) from 1994 to 2023. II, indica inbred rice; IH, indica hybrid rice; JI, japonica inbred rice; JH, japonica hybrid rice; IJH, indica-japonica hybrid rice.
Figure 8. Yield stability analysis of different varieties (A), and yield stability of indica inbred rice (B), indica hybrid rice (C), japonica inbred rice (D), japonica hybrid rice (E), and indica-japonica hybrid rice (F) from 1994 to 2023. II, indica inbred rice; IH, indica hybrid rice; JI, japonica inbred rice; JH, japonica hybrid rice; IJH, indica-japonica hybrid rice.
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Wang, H.; Bai, J.; Zhao, Q.; Tang, J.; Yang, R.; Cao, L.; Xiong, R. Changes in Rice Yield and Quality from 1994 to 2023 in Shanghai, China. Agronomy 2025, 15, 670. https://doi.org/10.3390/agronomy15030670

AMA Style

Wang H, Bai J, Zhao Q, Tang J, Yang R, Cao L, Xiong R. Changes in Rice Yield and Quality from 1994 to 2023 in Shanghai, China. Agronomy. 2025; 15(3):670. https://doi.org/10.3390/agronomy15030670

Chicago/Turabian Style

Wang, Haixia, Jianjiang Bai, Qi Zhao, Jianhao Tang, Ruifang Yang, Liming Cao, and Ruoyu Xiong. 2025. "Changes in Rice Yield and Quality from 1994 to 2023 in Shanghai, China" Agronomy 15, no. 3: 670. https://doi.org/10.3390/agronomy15030670

APA Style

Wang, H., Bai, J., Zhao, Q., Tang, J., Yang, R., Cao, L., & Xiong, R. (2025). Changes in Rice Yield and Quality from 1994 to 2023 in Shanghai, China. Agronomy, 15(3), 670. https://doi.org/10.3390/agronomy15030670

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