Response of Grain Yield and Water Use Efficiency to Irrigation Regimes during Mid-Season indica Rice Genotype Improvement
by
, , , and
Wenjiang Jing
1, 
Hao Wu
1,
Hanzhu Gu
1,
Zhilin Xiao
1,
Weilu Wang
1,
Weiyang Zhang
1,
Junfei Gu
1,
Lijun Liu
1,
Zhiqin Wang
1,
Jianhua Zhang
2,3,
Jianchang Yang
1 and
Hao Zhang
1,* 1
Jiangsu Key Laboratory of Crop Genetics and Physiology/Jiangsu Key Laboratory of Crop Cultivation and Physiology, Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, China
2
State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin 999077, China
3
Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong 999077, China
*
Author to whom correspondence should be addressed.
Agriculture 2022, 12(10), 1647; https://doi.org/10.3390/agriculture12101647
Submission received: 6 September 2022
/
Revised: 5 October 2022
/
Accepted: 7 October 2022
/
Published: 9 October 2022
(This article belongs to the Special Issue Crop Cultivation Physiology and Farmland Greenhouse Gas Emission Reduction)
Abstract
:Understanding the performance of rice (Oryza sativa L.) agronomic traits and efficiency in water usage as well as grain yield under various irrigation regimes is crucial to achieving high resource use efficiency and high yield. In this study, 12 mid-season indica rice genotypes that have been grown in the lower reaches of the Yangtze River for the past 80 years were studied in a field experiment for two years under two irrigation regimes, i.e., conventional irrigation (CI) and alternate wetting and drying irrigation (AWD). The results showed that with genotype improvement in irrigation regimes, the total number of spikelets, shoot and root dry weight, root oxidation activity, total leaf area index (LAI), effective LAI, leaf photosynthetic rate, and abscisic acid contents and zeatin + zeatin riboside contents in root bleeding sap were significantly increased at main growth stages. AWD irrigation synchronously increased rice resource use efficiency (water use efficiency (WUE), radiation use efficiency (RUE), and temperature use efficiency (TUE)) and grain yield. Compared to CI, AWD more significantly enhanced the performances of rice genotypes in all studied traits. Based on our findings, a semi-dwarf hybrid rice genotype has great potential for high resource use efficiency and high yield under alternate wetting and drying irrigation, which was attributed to the improved agronomic characteristics and superior root traits.
1. Introduction
Rice (Oryza sativa L.) is one of the three major global food crops and a staple food for more than 50% of the global population; so, it is important for food security [1,2]. China is the largest global rice producer, producing more than 28% of global rice [3,4]. Increasing grain yield per unit area has been the focus of global rice research. Since the beginning of the 21st century, the average increase rate of global annual rice grain yield is less than 1%; a few Asian countries have not increased their annual productivity [5,6]. In the past 80 years, the improvement of rice genotypes in China has developed into an early tall genotype, dwarf genotype, semi-dwarf genotype, and semi-dwarf hybrid. In addition, the grain yield of rice in China has significantly increased with improved genotypes. Over the last six decades, the average rice yield has increased from 2.0 t ha−1 to over 6.0 t ha−1 in China [7,8]. More research efforts should focus on developing new rice genotypes with a higher grain yield potential to boost the average farm yield [9,10,11].
Drought is one of the most serious global problems in agriculture. Agriculture in China is facing myriads of challenges, including irrigation water shortage and management and severe drought. Since rice is the largest water-consuming crop, water shortage is an important factor, limiting production [12,13,14,15]. Notably, water for rice irrigation accounts for an estimated 80% of total water consumption in Asia. Due to population growth, industrial development, climate change, and environmental pollution, a shortage in water resources for irrigation has suppressed the increase in rice production [16,17,18]. To improve water productivity while increasing grain yield, extensive studies on rice water demand and irrigation regimes under different cropping systems have been conducted [19]. A number of water-saving irrigation technologies have been developed, including alternate wetting and drying irrigation (AWD) [20], overhead irrigation [21], film-covering cultivation [22], and drought tolerance [23].
AWD irrigation has been widely used in rice production with significant positive effects on water saving. In AWD, the field is not continuously flooded; instead, after the pond has disappeared, the soil is allowed to dry out for one or more days before being re-flooded. The AWD irrigation regime has been employed in several Asian countries, including China, Bangladesh, India, and Vietnam. Importantly, AWD irrigation reduces water consumption by 30–35% [24]. The AWD irrigation regime has several benefits, including reduced water use, methane emissions, insect pests, and disease infestation, improved rice grain quality [25,26], and significant yield increases [27,28,29,30]. At present, studies on differences in response to AWD among rice genotypes are limited.
This study aimed to evaluate the performance in grain yield and water productivity of mid-season indica rice genotypes in the lower reaches of the Yangtze River in the last 80 years under AWD. We observed the number of tillers, LAI (total, effective, high effective LAI), leaf net photosynthetic rate, leaf transpiration rate, shoot and root biomasses, root–shoot ratio, root oxidation activity (ROA), abscisic acid (ABA) and zeatin (Z) + zeatin riboside (ZR) in root bleeding sap, and grain yield and its components. Subsequently, we analyzed the correlations of physiological and agronomic traits with grain yield and resource use efficiency. We believe that this research will offer a theoretical basis and guidance for achieving high rice yield and resource use efficiency through enhanced irrigation practices and improved rice genotype selection.
2. Materials and Methods
2.1. Experimental Site Description and Plant Materials
Field experiments were conducted at the research farm of Yangzhou University, Jiangsu Province, China (32°30′ N, 119°25′ E) during the rice growing season (May to October) between 2019 and 2020. The soil in the experimental field was a sandy loam texture with the following properties: 22.5 g kg−1 organic matter, 105.1 mg kg−1 alkali hydrolyzable N, 30.7 mg kg−1 Olsen-P, and 87.2 mg kg−1 exchangeable K. The amount of solar radiation and accumulated temperatures (temperature > 10 °C) from transplanting to maturity were 1906 MJ m−2 and 3287 °C in 2019 and 2015 MJ m−2 and 3251 °C in 2020, respectively. Weather conditions (mean air temperature, precipitation, and solar radiation) during the rice growing season were measured for two years at a weather station close to the experimental site (Table 1).
This study used 12 mid-season indica rice genotypes (including hybrid combinations) grown in the lower reaches of the Yangtze River over the past 80 years. These genotypes were selected because of their wide use; each had large planting area (>6.67 × 104 ha). The 12 rice genotypes were classified into four types, including early tall genotype (ET), dwarf genotype (DG), semi-dwarf genotype (SDG), and semi-dwarf hybrid (SDH) (Table 2). During the 2 years, seedlings were raised in a seedbed and sowed on 15th May, then transplanted on 10th June of both years at a hill spacing of 30.0 cm × 11 cm with two seedlings per hill. Plot size was in 5 m × 3 m. A total of 240 kg N ha−1 was used with a ratio of 4:2:2:2 at pre-transplanting, mid-tillering, panicle initiation, and spikelet differentiation stages, respectively. A day before transplanting, phosphorous (P2O5 13.5%) in CaH6O9P2 and potassium chloride (K2O 52.0%) were broadcast at a rate of 300 and 195 kg ha−1, respectively.
2.2. Treatment
The experiment was conducted as a split-plot design with two replications, with irrigation treatment being the main plot and genotypes as the subplot. The plot dimension was 5 m × 3 m. We implemented two irrigation regimes including conventional irrigation (CI) and alternate wetting and drying irrigation (AWD) 10 days after transplanting to maturity. In the CI regime, except for mid-tillering stage drainage, the water layer of 2.0–3.0 cm depth was added for one week before the final harvest. In the AWD regime, the plot field was not irrigated until the soil water potential reached (–15 ± 5) kPa at 15–20 cm depth. Five tension meters were installed in each plot, and readings were recorded at 1200 h. Water at 1.0–2.0 cm depth was flood-applied to the plots when soil water potential reached the threshold. Water and weeds, insects, and disease were strictly regulated to reduce the risk of yield loss.
2.3. Sampling and Measurements
A total of 20 plants were selected and tagged in each plot to observe tiller number at the mid-tillering, panicle initiation, heading, and maturity in both years. The percentage of productive tillers was the number of panicles developed from tillers as a percentage of the number of tillers at maturity.
In each plot, plants from five hills were sampled and separated into roots, leaves, stems, and sheaths to obtain root and shoot dry weight at mid-tillering, panicle initiation, heading, and maturity, respectively. The dry weight of each component was determined after drying at 70 °C for 72 h. After removing the leaves from the stem, the leaf area was immediately measured using an LI-3000 leaf area meter (LiCor Corporation, Lincoln, NE, USA).
Flag leaf net photosynthetic rate was measured at the panicle initiation, heading, and filling stages, respectively. Net photosynthetic and transpiration rates of the leaves were measured using the LI-6400 portable photosynthesis system (LiCor Corporation, Lincoln, NE, USA). The measurement was made between 0900 and 1200 h, i.e., when photosynthetic active radiation above the canopy was 1300–1500 μmol m−2 s−1. In total, 6 leaves were used per treatment.
For each root sampling, a 20 cm × 20 cm × 20 cm soil sample around each hill was dug up using a sampling core. Roots were separated from the retained core segments using a hydropneumatic elutriation device (Gillison’s Variety Fabrications, Benzonia, MI, USA). Root oxidation activity (ROA) was obtained by measuring alpha-naphthylamine (α-NA) oxidation as per the methods of Ramasamy et al. [31] and expressed as μg α-NA per gram dry weight (DW) per hour (μg α-NA g−1 DW h−1).
The root bleeding sap was collected from plants at panicle initiation, heading, and middle filling stages, respectively. The five plants selected in each plot were cut 10 cm above the soil level at 1800 h. Absorbent cotton was placed on the top of each decapitated stem and then covered with a polyethylene sheet. To prevent night dews and direct sunlight, a paper bag was used to cover the stems with absorbent cotton. At 0600 h the following morning, absorbent cotton with root bleeding sap was collected and the root bleeding weight was measured from the increase in absorbent cotton weight; root bleeding sap was extruded with a needle, then stored at −80 °C for hormonal assay. Zeatin (Z) + zeatin riboside (ZR) contents and abscisic acid (ABA) contents in root bleeding were measured based on the method described by Bollmark et al. [32].
Indexes described by Zhang et al. [33] were calculated as follows:
Radiation use efficiency (RUE, g MJ−1) = grain yield/amount of solar radiation from transplanting to maturity.
Temperature use efficiency (TUE, g °C−1 m−2) = grain yield/accumulated temperatures (temperature > 10 °C).
Grain yield-level water use efficiency (WUEG, kg m−3) = grain yield/the amount of irrigation water.
Leaf-level water use efficiency (WUEL, μmol mmol−1) = leaf net photosynthesis rate/leaf transpiration rate.
2.4. Final Harvest
The number of panicles per square meter, percentage of filled grains, and grain weight were determined from 50 plants (excluding the border ones) randomly sampled from each plot. Grain yield was determined from all plants in a 5 m2 area (except border plants) in each plot and then adjusted to a moisture content of 0.14 g H2O g−1 fresh weight. The percentage calculation of filled grains and the number of spikelets per panicle were obtained following the procedure by Zhang et al. [34].
2.5. Statistical Analysis
All data were processed with Microsoft Office Excel 2021 (Microsoft Corporation, Redmond, WA, USA), and analysis of variance (ANOVA) was performed using IBM SPSS Statistics software (v27, IBM Corporation, Armonk, NY, USA). Origin 2021 software (OriginLab Corporation, Northampton, MA, USA) was used for plotting. Pearson correlation analysis was performed in the R software (v4.2.1, R Foundation for Statistical Computing, Vienna, Austria). Means were tested by the least significant difference at p ≤ 0.05 (LSD0.05). Three-way ANOVA was performed on year (Y), irrigation (I), type (T), and their interactions (Y × I, Y × T, I × T, and Y × I × T).
3. Results
3.1. Three-Way Analysis of Variance (ANOVA)
In this study, year, irrigation, and type (early, dwarf, and semi-dwarf genotypes and semi-dwarf hybrids) were considered fixed effects. The grain yield and its components, WUEG, WUEL, RUE, TUE, and ROA were significantly different between years, irrigations, and types. There were no significant differences in number of tillers, LAI at HD, leaf net photosynthetic rate, root dry weight, ROA, ABA and Z + ZR contents in root bleeding between the interactions of years, irrigations, and types (Supplementary Table S1).
3.2. Grain Yield and Its Components
Under conventional irrigation (CI) as well as alternate wetting and drying irrigation (AWD), the grain yield gradually increased with the progress of improved rice genotypes. In contrast with CI, AWD significantly increased the grain yield of each type, with a similar trend across years (Figure 1, Table 3). AWD increased grain yield by 10.60%, 12.21%, 19.28%, and 9.71% in ET, DG, SDG, and SDH, respectively (Figure 1A). For the grain yield components, the increase in grain yield was primarily due to the increase in total spikelets (panicles × spikelets per panicle). Unlike CI, AWD decreased the number of panicles but increased the number of spikelets per panicle in all types of rice genotypes. An increase in the number of spikelets per panicle was greater than the decrease in the number of panicles. In 2019, AWD significantly increased the number of total spikelets by 7.68%, 8.06%, 10.80%, and 6.57% in ET, DG, SDG, and SDH, respectively, compared to CI (Table 3). The increase in the 1000-grain weight of Yangdao 6 and SDH was significant. The 1000-grain weight under AWD was 24.54 g, 24.37 g, 26.26 g, and 26.26 g in ET, DG, SDG, and SDH, respectively; this was 0.42%, 1.08%, 2.03%, and 2.07% higher than that under the CI (Table 3). The trend in the components of grain yield was similar during the two years.
3.3. Resource Use Efficiency
Similar to grain yield, the WUEG, RUE, and TUE under AWD were significantly higher than that under CI in two years (Table 4). Improvement of rice genotypes significantly increased leaf-level water use efficiency (WUEL). In contrast with CI, AWD significantly increased the WUEL by 12.95%, 10.72%, 6.85%, and 4.79% in ET, DG, SDG, and SDH at panicle initiation, respectively (Figure 2A). Trends of the remaining main growth stages were similar to that at panicle initiation (Figure 2A,B).
3.4. Number of Tillers and Leaf Area Index (LAI)
With the improvement of rice genotypes, the number of tillers significantly decreased under the two irrigation regimes. In contrast with CI, AWD significantly decreased the number of tillers and LAI in four types at the main growth stages (Table 5). LAI significantly increased with the improvement of rice genotypes. AWD exerted a significant effect on LAI at heading. In contrast with CI, AWD significantly increased the total LAI, effective LAI, and high effective LAI, respectively (Table 5).
3.5. Leaf Net Photosynthetic and Transpiration Rates
A significant effect on leaf net photosynthetic rate was noted under AWD. Unlike the CI, AWD significantly increased the leaf net photosynthetic rate in four types from panicle initiation to middle grain filling stage, respectively (Figure 3A,B). With the improvement of genotypes, the leaf transpiration rate significantly increased at panicle initiation and heading. The leaf transpiration rate under two irrigation regimes first increased then decreased at the middle grain filling stage with the improvement of rice genotypes. The leaf transpiration rate under AWD was lower than that under the CI in four varieties at panicle initiation and heading, respectively. In contrast with CI, AWD irrigation increased the leaf net photosynthetic rate in ET and DG and decreased it in SDG and SDH at the middle grain filling stage, respectively (Figure 3C,D).
3.6. Shoot Dry Weight, Root Dry Weight, Root–Shoot Ratio, and Root Oxidation Activity (ROA)
With the improvement of genotypes, the shoot dry weight significantly increased under the two irrigation regimes from panicle initiation to maturity. From panicle initiation to maturity, AWD increased the shoot dry weight in four types compared to CI (Figure 4A,B). The root dry weight in four types under CI was lower than that under AWD; it first increased, then decreased, with the progress in the growth stage (Figure 4C,D). At maturity, the root–shoot ratio showed no significant differences among different treatments or types (Figure 4E,F). In four types, the ROA under CI was significantly lower than that under AWD. In four types, the ROA under CI was much lower than that under AWD. At each main growth stage (panicle initiation, heading, and middle grain filling stage), the ROA in four types significantly increased with the improvement of rice genotypes (Figure 5).
3.7. Abscisic Acid (ABA) and Zeatin (Z) + Zeatin Riboside (ZR) in Root Bleeding
ABA and Z + ZR contents in root bleeding differed with two irrigation regimes at each main growth stage (panicle initiation, heading, and middle grain filling stage). The ABA and Z + ZR contents in root bleeding in all types gradually increased with the improvement of genotypes (Figure 6). In contrast with CI, AWD increased the ABA contents in four types, respectively (Figure 6A,B). The Z + ZR contents in root bleeding under two irrigation regimes first increased and then decreased from panicle initiation to middle grain filling stage. The Z + ZR contents under AWD were significantly higher than that under CI (Figure 6C,D).
3.8. Relationship between Agronomic and Physiological Traits with Grain Yield and Resource Use Efficiency
LAI (total, effective, high effective LAI), leaf net photosynthesis rate and leaf net photosynthesis rate at panicle initiation, heading, and middle grain filling stage, shoot and root dry weight at panicle initiation, heading, and maturity, ROA, ABA, and Z + ZR contents in root bleeding at panicle initiation, heading, and middle grain filling stage were significantly or very significant and positively correlated with grain yield, WUEG, RUE, and TUE. The number of tillers at panicle initiation, heading, and maturity was significantly or very significantly and negatively correlated with grain yield, WUEG, RUE, and TUE (Figure 7).
4. Discussion
4.1. Differences in Grain Yield and WUE among Genotypes
Increasing production while conserving precious water resources is crucial to China’s food security. The grain yield has been increased greatly with the corresponding cultivation techniques and improvement of rice varieties [35]. Planting numerous rice varieties could increase yield. The diversity of rice varieties contributes to the function and stability of food production systems. Stable food production systems are essential to provide sustainable food supplies and services [36]. It was reported that genetic improvement could improve within-variety level response diversity and adaptability, and resulted in highly robust varieties. High-yield modern varieties tend to be better adapted to harsh environments. So, the yield of modern varieties tends to be higher than that of old varieties under low-yield conditions [37,38]. In this study, we observed that grain yield was progressively increased with the improvement of mid-season indica rice genotypes, and yield increase was mainly attributed to obvious increases in the total number of spikelets, especially for semi-dwarf hybrids (Figure 1, Table 3). Therefore, it is an effective way to obtain higher yield to develop a greater sink size on the basis of enough panicles.
More and more freshwater resources were consumed with the increase in rice yield, so it is necessary to use the WUE of the rice itself to ensure the yield. Biological water saving means to carry out planned and scientific irrigation according to the water requirements of crops in different growth periods, so as to produce more food with less water, improving the WUE of the crops themselves. It may be the key and ultimate potential to achieve further water saving and increase in yield. In contrast with traditional varieties, modern varieties tend to have higher WUE [39]. This study showed that in the past 80 years, the WUE (both in terms of grain yield level and leaf level) was significantly increased with the improvement of mid-season indica rice genotypes in Jiangsu Province of China (Table 4, Figure 3). These results suggested that both high efficiency and high yield could be achieved coordinately through genetic improvement and breeding.
4.2. Response of Grain Yield and WUE to AWD among Genotypes
The morphological and physiological characteristics of the root system, aboveground growth development, water, and nutrient uptake, as well as utilization, have a direct impact on rice yield. AWD irrigation exerts different effects on rice yield. Several studies indicate that AWD irrigation preserves and even increases rice yield, with an average increase rate of approximately 6.00–12.63% [40,41,42]. Zhang et al. [24] adjusted the soil drying degree of the combination, and found that with rewatering when the soil was dried until the soil water potential was –15 kPa, the AWD irrigation could significantly increase the grain yield of rice. Elsewhere, another study found no significant difference in rice yield under AWD irrigation when the soil water was 15 cm below the soil surface compared with that under CI.
Nonetheless, another study revealed that AWD irrigation reduced the rice yield. A meta-analysis by Carrijo et al. [43] found that AWD irrigation reduced the rice grain yield compared to flood irrigation, with yield losses ranging between 3% and 23%. A previous study revealed that the grain yield of rice decreases but weeds increase under AWD if paddy fields are not timely irrigated. Meanwhile, AWD irrigation requires steady water sources, with complex drying and irrigation treatment, which is relatively difficult. As such, the implementation of this water-saving irrigation technology is limited [44]. Thus, additional research is necessary to understand the mechanisms by which AWD irrigation increases or decreases the rice yield. We found that AWD irrigation significantly increases the grain yield and WUE of all rice genotypes, with the improvement of genotypes compared to CI. Regarding the yield components, the increase in grain yield under AWD irrigation was primarily due to a simultaneous increase in the number of spikelets per panicle, percentage of filled grains, and 1000-grain weight (Table 3).
4.3. Response of Agronomic and Physiological Traits to AWD among Genotypes
Increasing the biomass production or harvest index or both increases the grain yield in cereals. Nevertheless, the importance of biomass production and harvest index in determining grain yield is debatable [45,46]. Our findings revealed that shoot dry matter increased with the improvement of rice genotypes, and AWD irrigation increased the shoot dry weight in all rice types (Figure 4A,B). Furthermore, our results confirm that modern rice genotypes have better LAI (total LAI, effective LAI, and high effective LAI) at heading, and higher leaf photosynthetic rate, root dry weight, and ROA than the old genotypes during the whole growth stages of rice (Table 5, Figure 2, Figure 4 and Figure 5). These findings show that as genotypes are enhanced, the source–sink relationship is hormonally developed with consistent advancement in population quality. A greater leaf photosynthetic rate and ROA may promote a greater dry matter production, consequently resulting in a higher grain yield for modern rice genotypes. A lower percentage of filled grains in modern rice genotypes may be attributed to a lower leaf photosynthetic rate and ROA during the grain filling stage. Zhang et al. [47] hypothesized that improving leaf photosynthesis and ROA during grain filling increases the percentage of filled grains in modern rice genotypes.
Additionally, the strong root physiological activity of rice is an important factor in its efficient water use. The ability of rice to efficiently utilize water correlates with root activity, root hormone concentration, and other physiological indicators of rice. ABA is an inhibitory plant hormone which plays an indispensable role in plant senescence and the shedding of organs (leaves, buds, and bolls). It plays a role in regulating the development and enrichment of grains [48]. As a class of key hormones as regulators of promoting cell division and delaying senescence, cytokinins are synthesized in roots and serve as a long-distance signals important for root-to-shoot communication. The changes in cytokinin concentrations in roots and xylem sap are closely related to the cytokinin-controlled processes in the shoots [49,50]. The ABA contents and Z + ZR contents in root bleeding of rice under AWD were higher than those of CI observed in this study. This indicates that mild water stress increases the ABA contents and Z + ZR contents in root bleeding and improves the adaptation of rice to the environment. Therefore, the combination of AWD irrigation in the process of improving rice genotypes enhances the morphological and physiological characteristics of the root system. It also improves the growth of the rice shoot, hence the grain yield and efficiency in resource usage.
5. Conclusions
There were differences in yield and WUE among rice genotypes, among which modern genotypes showed a strong advantage. The AWD could increase grain yield and resource use efficiencies including water, radiation, and temperature use efficiency, and the increase was the most for modern genotypes. The increased sink size, shoot and root biomasses, leaf area index, photosynthetic production of leaves, and vigorous root activity mainly contributed to the improvement of the yield and WUE under such an irrigation system for modern genotypes. In conclusion, the genotype improvement and AWD irrigation regime could achieve the dual goal of increasing grain yield and water use efficiency. The improved population quality and better root traits are the vital agronomic and physiological basis for modern rice genotypes to achieve high yield and water use efficiency under AWD.
Supplementary Materials
The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agriculture12101647/s1, Table S1: Significance of F values for fixed sources of variation for grain yield and main measurements.
Author Contributions
Conceptualization, L.L. and J.Y.; data curation, Z.X.; formal analysis, H.W.; funding acquisition, J.Z., J.Y. and H.Z.; methodology, J.G. and Z.W.; software, H.G. and W.W.; validation, W.Z.; writing—original draft preparation, W.J.; writing—review and editing, H.Z. All authors have read and agreed to the published version of the manuscript.
Funding
This work was funded by the National Natural Science Foundation of China (31871559, 32071944, 32272197), the Six Talent Peaks Project in Jiangsu Province (SWYY-151), the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the Interdisciplinary High Level Youth Support Project of Yangzhou University (2021), the Hong Kong Research Grants Council (GRF 14177617, 12103219, 12103220, AoE/M-403/16), and State Key Laboratory of Agrobiotechnology (Strategic Collaborative Projects) of the Chinese University of Hong Kong.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
Abbreviations
| CI | conventional irrigation |
| AWD | alternate wetting and drying |
| WUEG | grain yield-level water use efficiency |
| WUEL | leaf-level water use efficiency |
| RUE | radiation use efficiency |
| TUE | temperature use efficiency |
| LAI | leaf area index |
| ROA | root oxidation activity |
| ABA | abscisic acid |
| Z + ZR | zeatin + zeatin riboside |
| PI | panicle initiation stage |
| HD | heading stage |
| MF | middle grain filling stage |
| MA | maturity stage |
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Figure 1.
Effect of irrigation on grain yield of mid-season indica rice genotypes during the (A) 2019 and (B) 2020 growing seasons. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatment, respectively. * indicates significant differences at p ≤ 0.05.
Figure 1.
Effect of irrigation on grain yield of mid-season indica rice genotypes during the (A) 2019 and (B) 2020 growing seasons. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatment, respectively. * indicates significant differences at p ≤ 0.05.
Figure 2.
Leaf-level water use efficiency (A,B) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF represent panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 2.
Leaf-level water use efficiency (A,B) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF represent panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 3.
Flag leaf net photosynthetic rate (A,B) and transpiration rate (C,D) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF present panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 3.
Flag leaf net photosynthetic rate (A,B) and transpiration rate (C,D) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF present panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 4.
Shoot dry weight (A,B), root dry weight (C,D), and root–shoot ratio (E,F) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MA present panicle initiation, heading, and maturity, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 4.
Shoot dry weight (A,B), root dry weight (C,D), and root–shoot ratio (E,F) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MA present panicle initiation, heading, and maturity, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 5.
Root oxidation activities (A,B) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF represent panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 5.
Root oxidation activities (A,B) at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF represent panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 6.
The content of abscisic acid (ABA) (A,B) and zeatin (Z) + zeatin riboside (ZR) (C,D) in root bleeding at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF represent panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 6.
The content of abscisic acid (ABA) (A,B) and zeatin (Z) + zeatin riboside (ZR) (C,D) in root bleeding at three growth stages of mid-season indica rice genotypes under different irrigation treatments. CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatments, respectively. ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. PI, HD, and MF represent panicle initiation, heading, and middle grain filling stage, respectively. Vertical bars represent ± standard error of the mean where these exceed the size of the symbol. Different letters above the columns indicate significant differences (p ≤ 0.05) within the same measurement time.
Figure 7.
Pearson correlations of agronomic and physiological traits with grain yield and resource use efficiency of mid-season indica rice genotypes. WUEG, grain yield-level water use efficiency; WUEL, leaf-level water use efficiency; RUE, radiation use efficiency; TUE, temperature use efficiency; TN, tiller number; TLAI, total leaf area index; ELAI, effective leaf area index; HLAI, high effective leaf area index; LNPR, leaf net photosynthesis rate; LTR, leaf transpiration rate; SDW, shoot dry weight; RDW, root dry weight; RSR, root–shoot ratio; ROA, root oxidation activity; Ar, abscisic acid levels in root bleeding; Zr, zeatin + zeatin riboside levels in root bleeding; PI, panicle initiation; HD, heading; MF, middle grain filling stage; MA, maturity. Red and blue circles indicate negative and positive correlations between parameters, respectively. The darker the color, the higher the correlation. *, **, *** indicate significant differences at p ≤ 0.05, p ≤ 0.01, and p ≤ 0.001, respectively.
Figure 7.
Pearson correlations of agronomic and physiological traits with grain yield and resource use efficiency of mid-season indica rice genotypes. WUEG, grain yield-level water use efficiency; WUEL, leaf-level water use efficiency; RUE, radiation use efficiency; TUE, temperature use efficiency; TN, tiller number; TLAI, total leaf area index; ELAI, effective leaf area index; HLAI, high effective leaf area index; LNPR, leaf net photosynthesis rate; LTR, leaf transpiration rate; SDW, shoot dry weight; RDW, root dry weight; RSR, root–shoot ratio; ROA, root oxidation activity; Ar, abscisic acid levels in root bleeding; Zr, zeatin + zeatin riboside levels in root bleeding; PI, panicle initiation; HD, heading; MF, middle grain filling stage; MA, maturity. Red and blue circles indicate negative and positive correlations between parameters, respectively. The darker the color, the higher the correlation. *, **, *** indicate significant differences at p ≤ 0.05, p ≤ 0.01, and p ≤ 0.001, respectively.
Table 1.
Mean air temperature, precipitation, and solar radiation during the rice growing season.
| Month | Mean Air Temperature † (°C) | Precipitation ‡ (mm per Month) | Solar Radiation § (MJ m−2 per Month) | |||
|---|---|---|---|---|---|---|
| 2019 | 2020 | 2019 | 2020 | 2019 | 2020 | |
| June | 25.6 | 25.8 | 121 | 253 | 504 | 535 |
| July | 28.4 | 25.5 | 221 | 186 | 476 | 542 |
| August | 28.3 | 30.4 | 222 | 246 | 540 | 517 |
| September | 23.5 | 23.8 | 72.4 | 50.2 | 407 | 427 |
| October | 17.9 | 16.7 | 56.1 | 56.9 | 337 | 377 |
† Mean air temperature value is the monthly average. ‡ Precipitation value is monthly total. § Sunshine hour value is monthly total.
Table 2.
The tested mid-season indica rice genotypes in this study.
| Application Years | Variety | Type | Growth Period (d) |
|---|---|---|---|
| 1940–1950 | Huangguaxian | Early tall genotype | 125 |
| 1950–1960 | Yintiaoxian | Early tall genotype | 127 |
| 1950–1960 | Nanjing 1 | Early tall genotype | 125 |
| 1960–1970 | Taizhongxian | Dwarf genotype | 138 |
| 1960–1970 | Nanjing 11 | Dwarf genotype | 129 |
| 1960–1970 | Zhenzhu’ai | Dwarf genotype | 136 |
| 1970–1980 | IR 24 | Semi-dwarf genotype | 143 |
| 1980–1990 | Yangdao 2 | Semi-dwarf genotype | 142 |
| 1990–2000 | Yangdao 6 | Semi-dwarf genotype | 142 |
| 2000–2005 | Yangliangyou 6 | Semi-dwarf hybrid | 141 |
| 2000–2005 | Liangyoupeijiu | Semi-dwarf hybrid | 145 |
| 2000–2005 | II you 084 | Semi-dwarf hybrid | 145 |
Table 3.
Effect of irrigation on grain yield components of mid-season indica rice genotypes during the 2019 and 2020 growing seasons.
Table 3.
Effect of irrigation on grain yield components of mid-season indica rice genotypes during the 2019 and 2020 growing seasons.
| Treatment † | Type ‡ | Variety | No. of Panicles (×104 ha−1) | Spikelets per Panicle | Total Spikelets (×106 ha−1) | Filled Grains (%) | 1000-Grain Weight (g) |
|---|---|---|---|---|---|---|---|
| 2019 | |||||||
| CI | ET | Huangguaxian | 252.72 e § | 114.67 i | 285.23 l | 66.03 d | 24.28 e |
| Yintiaoxian | 298.08 a | 106.40 j | 317.15 j | 66.31 d | 24.69 d | ||
| Nanjing 1 | 255.96 d | 118.64 h | 303.62 k | 67.12 d | 24.33 e | ||
| Average | 268.92 | 113.24 | 302.00 | 66.49 | 24.43 | ||
| DG | Taizhongxian | 275.40 c | 141.93 g | 390.57 e | 82.05 b | 23.36 f | |
| Nanjing 11 | 249.48 f | 156.33 e | 383.22 g | 77.90 c | 24.62 d | ||
| Zhenzhu’ai | 220.32 j | 160.63 d | 344.67 i | 78.53 c | 24.34 e | ||
| Average | 248.40 | 152.96 | 372.82 | 79.49 | 24.11 | ||
| SDG | IR 24 | 288.36 b | 152.92 f | 441.11 c | 66.42 d | 24.68 d | |
| Yangdao 2 | 239.76 g | 162.13 d | 387.85 f | 85.05 a | 24.50 de | ||
| Yangdao 6 | 230.04 i | 155.91 e | 358.58 h | 85.02 a | 28.02 b | ||
| Average | 252.72 | 156.99 | 395.85 | 78.83 | 25.73 | ||
| SDH | Yangliangyou 6 | 210.60 k | 196.95 a | 413.95 d | 82.93 b | 28.85 a | |
| Liangyoupeijiu | 236.52 h | 191.96 b | 454.28 b | 85.07 a | 25.93 c | ||
| II you 084 | 252.72 e | 180.97 c | 455.62 a | 85.02 a | 27.82 b | ||
| Average | 233.28 | 189.96 | 441.28 | 84.34 | 27.53 | ||
| AWD | ET | Huangguaxian | 249.48 d | 122.29 k | 304.68 l | 66.20 g | 24.45 g |
| Yintiaoxian | 291.60 a | 109.78 l | 319.69 k | 68.41 f | 24.70 f | ||
| Nanjing 1 | 243.00 e | 144.57 j | 351.25 j | 69.33 f | 24.46 g | ||
| Average | 261.36 | 125.55 | 325.21 | 67.98 | 24.54 | ||
| DG | Taizhongxian | 265.68 c | 151.95 i | 402.78 h | 82.71 c | 23.62 h | |
| Nanjing 11 | 233.28 f | 166.49 h | 387.92 i | 78.54 d | 24.94 e | ||
| Zhenzhu’ai | 210.60 i | 198.63 e | 417.96 f | 84.01 c | 24.54 fg | ||
| Average | 236.52 | 172.36 | 402.89 | 81.75 | 24.37 | ||
| SDG | IR 24 | 272.16 b | 169.70 g | 461.69 c | 74.20 e | 25.99 d | |
| Yangdao 2 | 217.08 h | 204.43 c | 440.57 e | 86.66 ab | 24.66 fg | ||
| Yangdao 6 | 220.32 g | 188.10 f | 413.58 g | 87.27 a | 28.12 b | ||
| Average | 236.52 | 187.41 | 438.61 | 82.71 | 26.26 | ||
| SDH | Yangliangyou 6 | 207.36 j | 214.56 b | 442.52 d | 83.82 c | 28.93 a | |
| Liangyoupeijiu | 210.60 i | 227.40 a | 478.94 b | 85.51 b | 27.23 c | ||
| II you 084 | 243.00 e | 202.09 d | 489.40 a | 85.71 b | 28.15 b | ||
| Average | 220.32 | 214.68 | 470.29 | 85.01 | 28.10 | ||
| 2020 | |||||||
| CI | ET | Huangguaxian | 264.80 g | 104.72 i | 277.16 l | 59.58 i | 26.09 e |
| Yintiaoxian | 257.01 e | 109.46 h | 281.58 j | 56.20 j | 25.88 e | ||
| Nanjing 1 | 249.22 c | 104.09 i | 260.80 k | 57.99 h | 25.89 d | ||
| Average | 257.01 | 106.09 | 273.18 | 57.92 | 25.95 | ||
| DG | Taizhongxian | 247.66 h | 124.95 g | 309.31 i | 75.89 d | 24.95 gh | |
| Nanjing 11 | 255.45 f | 144.88 d | 367.21 f | 65.11 g | 26.13 d | ||
| Zhenzhu’ai | 275.70 b | 130.89 f | 360.39 g | 70.36 e | 25.08 g | ||
| Average | 259.60 | 133.57 | 345.64 | 70.45 | 25.39 | ||
| SDG | IR 24 | 283.49 a | 155.68 c | 441.31 b | 68.70 f | 25.01 gh | |
| Yangdao 2 | 246.11 i | 154.51 c | 376.76 e | 85.08 a | 25.59 f | ||
| Yangdao 6 | 263.24 d | 135.75 e | 352.45 h | 84.08 ab | 29.10 a | ||
| Average | 264.28 | 148.65 | 390.17 | 79.29 | 26.57 | ||
| SDH | Yangliangyou 6 | 235.20 j | 168.25 b | 391.32 d | 80.67 c | 28.75 b | |
| Liangyoupeijiu | 249.22 g | 186.84 a | 464.67 a | 81.33 c | 24.90 h | ||
| II you 084 | 225.86 k | 187.39 a | 423.17 c | 83.40 b | 26.62 c | ||
| Average | 236.76 | 180.83 | 426.39 | 81.80 | 26.76 | ||
| AWD | ET | Huangguaxian | 252.34 e | 125.63 i | 317.28 l | 59.74 g | 26.59 e |
| Yintiaoxian | 250.78 d | 116.10 h | 292.50 k | 63.79 g | 25.90 f | ||
| Nanjing 1 | 242.99 c | 111.42 g | 271.07 j | 64.88 h | 26.15 c | ||
| Average | 248.70 | 117.72 | 293.62 | 62.80 | 26.21 | ||
| DG | Taizhongxian | 239.88 f | 138.63 f | 332.94 i | 80.25 c | 25.15 g | |
| Nanjing 11 | 250.78 d | 148.50 e | 372.02 h | 72.10 e | 26.44 d | ||
| Zhenzhu’ai | 253.89 b | 148.40 e | 376.40 g | 78.30 d | 26.18 e | ||
| Average | 248.18 | 145.18 | 360.45 | 76.88 | 25.92 | ||
| SDG | IR 24 | 274.14 a | 164.56 c | 451.17 c | 70.28 f | 25.18 g | |
| Yangdao 2 | 239.88 f | 166.27 c | 397.88 e | 85.03 a | 25.95 f | ||
| Yangdao 6 | 242.99 e | 157.38 d | 379.52 f | 84.87 a | 29.16 a | ||
| Average | 252.34 | 162.74 | 409.52 | 80.06 | 26.76 | ||
| SDH | Yangliangyou 6 | 221.18 h | 196.60 b | 432.28 d | 81.10 c | 28.87 b | |
| Liangyoupeijiu | 242.99 e | 196.85 b | 476.39 a | 82.27 b | 26.03 ef | ||
| II you 084 | 224.30 g | 215.68 a | 469.11 b | 85.63 a | 26.71 c | ||
| Average | 229.49 | 203.04 | 459.26 | 83.00 | 27.20 | ||
† CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatment, respectively. ‡ ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. § Different letters indicate statistical significance at p ≤ 0.05 (n = 4) within the same year and irrigation regime.
Table 4.
Effect of irrigation on grain yield-level water use efficiency (WUEG), radiation use efficiency (RUE), and temperature use efficiency (TUE) of mid-season indica rice genotypes during the 2019 and 2020 growing seasons.
Table 4.
Effect of irrigation on grain yield-level water use efficiency (WUEG), radiation use efficiency (RUE), and temperature use efficiency (TUE) of mid-season indica rice genotypes during the 2019 and 2020 growing seasons.
| Treatment † | Type ‡ | Variety | WUEG (kg m−3) | RUE (g MJ−1) | TUE (g °C−1 m−2) |
|---|---|---|---|---|---|
| 2019 | |||||
| CI | ET | Huangguaxian | 0.61 h § | 0.24 h | 0.14 h |
| Yintiaoxian | 0.69 g | 0.27 g | 0.16 g | ||
| Nanjing 1 | 0.66 gh | 0.26 gh | 0.15 gh | ||
| Average | 0.65 | 0.26 | 0.15 | ||
| DG | Taizhongxian | 1.00 e | 0.39 e | 0.23 e | |
| Nanjing 11 | 0.98 e | 0.39 e | 0.22 e | ||
| Zhenzhu’ai | 0.88 f | 0.35 f | 0.20 f | ||
| Average | 0.95 | 0.38 | 0.22 | ||
| SDG | IR 24 | 0.96 e | 0.38 e | 0.22 e | |
| Yangdao 2 | 1.08 d | 0.42 d | 0.25 d | ||
| Yangdao 6 | 1.14 c | 0.45 c | 0.26 c | ||
| Average | 1.06 | 0.42 | 0.24 | ||
| SDH | Yangliangyou 6 | 1.32 b | 0.52 b | 0.30 b | |
| Liangyoupeijiu | 1.34 b | 0.53 b | 0.30 b | ||
| II you 084 | 1.44 a | 0.57 a | 0.33 a | ||
| Average | 1.36 | 0.54 | 0.31 | ||
| AWD | ET | Huangguaxian | 0.93 k | 0.26 k | 0.15 k |
| Yintiaoxian | 1.02 j | 0.28 j | 0.16 j | ||
| Nanjing 1 | 1.12 i | 0.31 i | 0.18 i | ||
| Average | 1.02 | 0.28 | 0.17 | ||
| DG | Taizhongxian | 1.48 h | 0.41 h | 0.24 h | |
| Nanjing 11 | 1.43 h | 0.40 h | 0.23 h | ||
| Zhenzhu’ai | 1.63 g | 0.45 g | 0.26 g | ||
| Average | 1.51 | 0.42 | 0.24 | ||
| SDG | IR 24 | 1.68 f | 0.47 f | 0.27 f | |
| Yangdao 2 | 1.78 e | 0.49 e | 0.29 e | ||
| Yangdao 6 | 1.92 d | 0.53 d | 0.31 d | ||
| Average | 1.79 | 0.50 | 0.29 | ||
| SDH | Yangliangyou 6 | 2.02 c | 0.56 c | 0.33 c | |
| Liangyoupeijiu | 2.10 b | 0.58 b | 0.34 b | ||
| II you 084 | 2.23 a | 0.62 a | 0.36 a | ||
| Average | 2.12 | 0.59 | 0.34 | ||
| 2020 | |||||
| CI | ET | Huangguaxian | 0.57 g | 0.21 g | 0.13 g |
| Yintiaoxian | 0.54 g | 0.20 g | 0.13 g | ||
| Nanjing 1 | 0.52 g | 0.19 g | 0.12 g | ||
| Average | 0.55 | 0.20 | 0.13 | ||
| DG | Taizhongxian | 0.78 f | 0.29 f | 0.18 f | |
| Nanjing 11 | 0.83 ef | 0.31 ef | 0.19 ef | ||
| Zhenzhu’ai | 0.85 e | 0.31 e | 0.20 e | ||
| Average | 0.82 | 0.30 | 0.19 | ||
| SDG | IR 24 | 1.01 d | 0.38 d | 0.23 d | |
| Yangdao 2 | 1.09 c | 0.41 c | 0.25 c | ||
| Yangdao 6 | 1.15 b | 0.43 b | 0.27 b | ||
| Average | 1.08 | 0.40 | 0.25 | ||
| SDH | Yangliangyou 6 | 1.21 a | 0.45 a | 0.28 a | |
| Liangyoupeijiu | 1.25 a | 0.47 a | 0.29 a | ||
| II you 084 | 1.25 a | 0.47 a | 0.29 a | ||
| Average | 1.24 | 0.46 | 0.29 | ||
| AWD | ET | Huangguaxian | 0.86 g | 0.23 g | 0.14 g |
| Yintiaoxian | 0.91 g | 0.24 g | 0.15 g | ||
| Nanjing 1 | 0.95 g | 0.25 g | 0.15 g | ||
| Average | 0.91 | 0.24 | 0.15 | ||
| DG | Taizhongxian | 1.26 f | 0.33 f | 0.21 f | |
| Nanjing 11 | 1.34 f | 0.35 f | 0.22 f | ||
| Zhenzhu’ai | 1.46 e | 0.38 e | 0.24 e | ||
| Average | 1.35 | 0.36 | 0.22 | ||
| SDG | IR 24 | 1.51 e | 0.40 e | 0.25 e | |
| Yangdao 2 | 1.66 d | 0.44 d | 0.27 d | ||
| Yangdao 6 | 1.77 c | 0.47 c | 0.29 c | ||
| Average | 1.64 | 0.43 | 0.27 | ||
| SDH | Yangliangyou 6 | 1.91 b | 0.50 b | 0.31 b | |
| Liangyoupeijiu | 1.92 b | 0.50 b | 0.31 b | ||
| II you 084 | 2.03 a | 0.53 a | 0.33 a | ||
| Average | 1.95 | 0.51 | 0.32 |
† CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatment, respectively. ‡ ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. § Different letters indicate statistical significance at p ≤ 0.05 (n = 4) within the same year and irrigation regime.
Table 5.
Effect of irrigation on number of tillers and leaf area index at heading of mid-season indica rice genotypes during the in 2019 and 2020 growing seasons.
Table 5.
Effect of irrigation on number of tillers and leaf area index at heading of mid-season indica rice genotypes during the in 2019 and 2020 growing seasons.
| Treatment † | Type ‡ | Variety | Number of Tillers and Mail Stems per m2 | LAI | ||||
|---|---|---|---|---|---|---|---|---|
| Panicle Initiation | Heading | Maturity | Total LAI | Effective LAI | High Effective LAI | |||
| 2019 | ||||||||
| CI | ET | Huangguaxian | 385 b § | 277 c | 253 cd | 5.22 def | 3.94 fgh | 3.72 def |
| Yintiaoxian | 431 a | 329 a | 298 a | 5.04 ef | 3.80 gh | 3.56 ef | ||
| Nanjing 1 | 380 b | 282 c | 256 c | 4.76 f | 3.59 h | 3.41 f | ||
| Average | 399 | 296 | 269 | 5.01 | 3.78 | 3.56 | ||
| DG | Taizhongxian | 371 b | 303 b | 288 ab | 5.67 cd | 4.58 de | 4.08 cd | |
| Nanjing 11 | 380 b | 277 c | 240 def | 5.41 cde | 4.37 ef | 3.90 cde | ||
| Zhenzhu’ai | 298 cd | 244 e | 230 fg | 5.21 def | 4.20 efg | 3.77 cdef | ||
| Average | 350 | 275 | 253 | 5.43 | 4.38 | 3.92 | ||
| SDG | IR 24 | 381 b | 318 ab | 275 b | 5.71 cd | 5.16 c | 4.13 cd | |
| Yangdao 2 | 304 cd | 252 de | 249 cde | 5.84 c | 5.00 cd | 4.21 c | ||
| Yangdao 6 | 290 d | 242 e | 220 gh | 6.41 b | 5.79 b | 4.66 b | ||
| Average | 325 | 271 | 248 | 5.99 | 5.32 | 4.33 | ||
| SDH | Yangliangyou 6 | 270 e | 222 f | 211 h | 6.89 ab | 6.23 ab | 5.04 ab | |
| Liangyoupeijiu | 294 cd | 249 e | 237 ef | 7.17 a | 6.48 a | 5.25 a | ||
| II you 084 | 310 c | 266 cd | 253 cd | 6.97 ab | 6.31 a | 5.09 a | ||
| Average | 291 | 246 | 233 | 7.01 | 6.34 | 5.13 | ||
| AWD | ET | Huangguaxian | 372 b | 266 c | 249 cd | 5.31 d | 4.80 d | 4.26 c |
| Yintiaoxian | 403 a | 311 a | 292 a | 5.43 cd | 4.91 cd | 4.41 c | ||
| Nanjing 1 | 344 c | 259 cd | 243 d | 5.41 cd | 4.89 cd | 4.38 c | ||
| Average | 373 | 279 | 261 | 5.38 | 4.87 | 4.35 | ||
| DG | Taizhongxian | 346 c | 283 b | 268 bc | 5.95 bcd | 5.38 bcd | 4.88 bc | |
| Nanjing 11 | 347 c | 248 d | 238 de | 6.47 abcd | 5.85 abcd | 5.37 abc | ||
| Zhenzhu’ai | 283 d | 225 e | 221 ef | 7.12 ab | 6.44 ab | 5.84 ab | ||
| Average | 325 | 252 | 242 | 6.51 | 5.89 | 5.36 | ||
| SDG | IR 24 | 344 c | 290 b | 272 b | 6.84 abc | 6.18 abc | 5.61 ab | |
| Yangdao 2 | 265 ef | 225 e | 217 f | 7.35 ab | 6.64 ab | 5.93 ab | ||
| Yangdao 6 | 268 def | 228 e | 220 ef | 7.3 ab | 6.60 ab | 5.93 ab | ||
| Average | 292 | 248 | 237 | 7.16 | 6.47 | 5.82 | ||
| SDH | Yangliangyou 6 | 253 f | 213 e | 207 f | 7.51 a | 6.79 a | 6.22 a | |
| Liangyoupeijiu | 253 f | 217 e | 211 f | 7.69 a | 6.95 a | 6.40 a | ||
| II you 084 | 279 de | 252 cd | 243 d | 7.31 ab | 6.61 ab | 6.06 ab | ||
| Average | 262 | 227 | 220 | 7.50 | 6.78 | 6.23 | ||
| 2020 | ||||||||
| CI | ET | Huangguaxian | 405 a | 285 abc | 282 a | 4.88 f | 3.55 h | 3.64 de |
| Yintiaoxian | 373 b | 282 bcd | 246 cd | 5.47 de | 3.93 g | 3.51 e | ||
| Nanjing 1 | 370 bc | 280 bcd | 262 bc | 5.11 ef | 4.18 fg | 3.42 e | ||
| Average | 383 | 282 | 263 | 5.15 | 3.89 | 3.52 | ||
| DG | Taizhongxian | 339 d | 259 ef | 261 bc | 5.57 de | 4.16 fg | 3.97 bcd | |
| Nanjing 11 | 362 c | 266 cde | 256 bcd | 4.95 f | 4.58 de | 3.82 cde | ||
| Zhenzhu’ai | 370 bc | 294 ab | 251 bcd | 5.64 d | 4.39 ef | 3.80 cde | ||
| Average | 357 | 273 | 256 | 5.39 | 4.38 | 3.86 | ||
| SDG | IR 24 | 361 c | 304 a | 246 cd | 5.76 d | 5.24 c | 4.03 bcd | |
| Yangdao 2 | 304 f | 263 de | 253 bcd | 6.63 bc | 4.87 d | 4.14 bc | ||
| Yangdao 6 | 322 e | 250 ef | 268 ab | 6.42 c | 5.76 b | 4.36 b | ||
| Average | 329 | 272 | 255 | 6.27 | 5.29 | 4.18 | ||
| SDH | Yangliangyou 6 | 291 g | 250 ef | 241 d | 6.81 bc | 5.86 b | 5.13 a | |
| Liangyoupeijiu | 304 f | 265 de | 248 cd | 7.32 a | 6.28 a | 5.11 a | ||
| II you 084 | 275 h | 241 f | 223 e | 7.09 ab | 6.39 a | 5.16 a | ||
| Average | 290 | 252 | 237 | 7.07 | 6.18 | 5.13 | ||
| AWD | ET | Huangguaxian | 381 a | 271 a | 250 ab | 4.97 f | 4.17 h | 3.83 g |
| Yintiaoxian | 357 b | 268 ab | 258 a | 5.23 ef | 4.89 g | 4.39 f | ||
| Nanjing 1 | 351 bc | 260 abc | 252 ab | 5.48 de | 4.72 g | 4.48 f | ||
| Average | 363 | 266 | 253 | 5.23 | 4.59 | 4.23 | ||
| DG | Taizhongxian | 312 d | 256 abcd | 239 bc | 5.84 d | 5.29 f | 4.89 e | |
| Nanjing 11 | 356 b | 268 ab | 250 ab | 6.41 c | 5.75 e | 5.36 d | ||
| Zhenzhu’ai | 339 c | 252 bcde | 253 ab | 6.68 c | 6.32 cd | 5.44 d | ||
| Average | 336 | 259 | 247 | 6.31 | 5.79 | 5.23 | ||
| SDG | IR 24 | 339 c | 252 bcde | 262 a | 6.82 bc | 6.39 bcd | 5.44 d | |
| Yangdao 2 | 281 e | 246 cde | 239 bc | 7.18 ab | 6.14 d | 5.98 c | ||
| Yangdao 6 | 292 e | 259 abc | 232 cd | 7.31 a | 6.66 abc | 6.26 abc | ||
| Average | 304 | 253 | 244 | 7.10 | 6.40 | 5.89 | ||
| SDH | Yangliangyou 6 | 266 f | 235 e | 218 d | 7.18 ab | 6.18 d | 6.16 bc | |
| Liangyoupeijiu | 290 e | 241 de | 241 bc | 7.46 a | 6.72 ab | 6.46 ab | ||
| II you 084 | 265 f | 241 de | 222 d | 7.62 a | 6.93 a | 6.58 a | ||
| Average | 273 | 239 | 227 | 7.42 | 6.61 | 6.40 | ||
† CI and AWD represent conventional irrigation treatment and alternate wetting and drying irrigation treatment, respectively. ‡ ET denotes early tall genotype, DG denotes dwarf genotype, SDG denotes semi-dwarf genotype, and SDH denotes semi-dwarf hybrid. § Different letters indicate statistical significance at p ≤ 0.05 (n = 4) within the same year and irrigation regime.
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Jing, W.; Wu, H.; Gu, H.; Xiao, Z.; Wang, W.; Zhang, W.; Gu, J.; Liu, L.; Wang, Z.; Zhang, J.; et al. Response of Grain Yield and Water Use Efficiency to Irrigation Regimes during Mid-Season indica Rice Genotype Improvement. Agriculture 2022, 12, 1647. https://doi.org/10.3390/agriculture12101647
AMA Style
Jing W, Wu H, Gu H, Xiao Z, Wang W, Zhang W, Gu J, Liu L, Wang Z, Zhang J, et al. Response of Grain Yield and Water Use Efficiency to Irrigation Regimes during Mid-Season indica Rice Genotype Improvement. Agriculture. 2022; 12(10):1647. https://doi.org/10.3390/agriculture12101647
Chicago/Turabian StyleJing, Wenjiang, Hao Wu, Hanzhu Gu, Zhilin Xiao, Weilu Wang, Weiyang Zhang, Junfei Gu, Lijun Liu, Zhiqin Wang, Jianhua Zhang, and et al. 2022. "Response of Grain Yield and Water Use Efficiency to Irrigation Regimes during Mid-Season indica Rice Genotype Improvement" Agriculture 12, no. 10: 1647. https://doi.org/10.3390/agriculture12101647
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