Indica Hybrid Research Articles

Fate of Basal N Under Split Fertilization in Rice with 15N Isotope Tracer

Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen (N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understanding of the basal N fate under split fertilization is crucial for determining rational basal N split ratio to improve the yield and reduce the loss to environment. A two-year field experiment with two N rates of 150 and 300 kg N ha−1, two split ratios of basal N, 40% and 25%, and two rice varieties, Wuyunjing 23 (japonica) and Y-liangyou 2 (super hybrid indica), was conducted. Labelled 15N urea was supplied in micro-plots as basal fertilizer to determine the plant uptake, translocation, soil residual, and loss of basal N fertilizer. The results showed that basal N absorbed by rice was only 1.6%–11.5% before tillering fertilization (8–10 d after transplanting), 6.5%–21.4% from tillering fertilization to panicle fertilization, and little (0.1%–4.4%) after panicle fertilization. The recovery efficiency of basal N for the entire rice growth stage was low and ranged from 18.7% to 24.8%, not significantly affected by cultivars or N treatments. Soil residual basal N accounted for 10.3%–36.4% and decreased with increasing total N rate and basal N ratio, regardless of variety and year. 43.8%–70.4% of basal N was lost into the environment based on the N balance. Basal N loss was significantly linearly positive related with the basal N rate and obviously enhanced by the increasing basal N ratio for both varieties in both 2012 and 2013. The N use efficiency and yield was significantly improved when decreasing the basal N ratio from 40% to 25%. The results indicated that the basal N ratio should be reduced, especially with limited N inputs, to improve the yield and reduce the N loss to the environment.

Comparison of yield traits in rice among three mechanized planting methods in a rice-wheat rotation system

Understanding the differences in yield traits of rice among pothole seedling of mechanical transplanting (PSMT), carpet seedling of mechanical transplanting (CSMT) and mechanical direct seeding (MDS) is of great importance not only for rice scientists but also for rice farmers to develop a high-yield production system under mechanical conditions in a rice-wheat rotation system. However, such traits are yet to be studied among rice varieties of japonica-indica hybrid rice (JIHR), japonica conventional rice (JCR) and indica hybrid rice (IHR). Field experiments were conducted in 2014 and 2015, where six cultivars of the three rice types JIHR, JCR and IHR were grown individually with PSMT, CSMT and MDS methods, under respective managements for each method to achieve the maximum attainable yield. Results showed that (i) the PSMT significantly increased grain yield of JIHR by 22.0 and 7.1%, of JCR by 15.6 and 3.7% and of IHR by 22.5 and 7.4%, compared to MDS and CSMT on average across the two years, respectively. The highest yield was produced by the combination of JIHR and PSMT; (ii) high yield under PSMT was mainly attributed to large sink capacity and high-efficient dry matter accumulation. With sufficient panicles per hectare, the increase of spikelet number per panicle, especially the increase in spikelet number of the secondary rachis-branches was determined to be the optimal approach for developing a large sink capacity for rice under PSMT. The optimal tillers development, large leaf area index at heading stage, and high leaf area duration, crop growth rate and net assimilation rate during grain-filling phase could be the cause of sufficient dry matter accumulation for rice under PSMT; (iii) moreover, the PSMT favored plant growth as well as enriched the stems plus sheaths during grain-filling phase, as compared with CSMT and MDS. These results suggest that PSMT may be an alternative approach to increasing grain yield in a rice-wheat rotation system in the lower reaches of the Yangtze River in China.

Characterization and evaluation of rice blast resistance of Chinese indica hybrid rice parental lines

The development of resistant varieties and hybrid combinations has been the most effective and economical strategy to control blast disease caused by Magnaporthe oryzae. However, the distribution of major R genes and blast resistance characterization in hybrid rice parents has not been well investigated, resulting in their limited use in hybrid rice blast-resistance breeding. In the present study, 88 elite indica hybrid rice parental lines were evaluated with 30 isolates of M. oryzae collected from the main planting area of indica hybrid rice in China and were characterized for the presence of 11 major resistance genes using molecular markers. The pathogenicity assays showed that four types of hybrid rice parent line showed some resistance to M. oryzae. However, the proportions of highly resistant lines and the mean resistance frequency (RF) varied among the four types, with resistance in decreasing order shown by three-line restorer lines, three-line maintainer lines, two-line sterile lines, and two-line restorer lines. All 88 hybrid rice parental lines carried more than one R gene, but none carried the R genes Pi1 and Pi2. Although Pid3 and Pi9 were present only in three-line restorer lines and Pigm only in three-line maintainer lines, the remaining six R genes (Pib, Pid2, Pi5, Pia, Pi54, and Pita) were present in the four types of hybrid rice parent with significantly different distribution frequencies. The correlation between R genes and resistance reactions was investigated. The results are expected to provide useful information for rational utilization of major R genes in hybrid rice breeding programs.

In vitro starch digestibility of rice flour is not affected by method of cooking

This study evaluated the effects of different cooking methods on in vitro starch digestibility of three rice varieties. Results from differential scanning calorimetry and X-ray diffraction of cooked rice flours showed that rice starch was completely gelatinized after cooking. The overall paste viscosities of cooked indica hybrid flour (IHF) and japonica flour (JF) were lower than those of their corresponding raw flours. However, cooked waxy flour (WF) showed much higher paste viscosities than raw flours, especially the viscosity at the start of RVA testing. Cooking increased greatly the rate and extent of starch digestion of IHF and JF, but had a small effect on WF. There were small differences in rate and extent of starch digestion of rice after cooking under various conditions. Cooking methods were found to have little effect on in vitro starch digestibility of rice. Viscosity of the gelatinized waxy starch matrix affected in vitro starch digestibility. This study enables us to gain a better understanding of cooking effects on in vitro digestibility of starch in rice flour.

Multi-scale structures and functional properties of starches from Indica hybrid, Japonica and waxy rice

The structural and functional properties of starches from three rice grains differing in amylose content (19.9, 13.4 and 0.8% for Japonica, Indica hybrid and waxy rice, respectively) were investigated using a range of characterization methods Indica hybrid starch (IHS) had the highest proportion of intermediate (DP 13–24) and long branch chains (DP≥37) and the lowest proportion of short branch chains (DP 6–12), whereas the opposite results were observed for Japonica starch (JS). The results for waxy rice starch (WS) were between those of IHS and JS. Rice starches showed a typical A-type X-ray diffraction pattern with the relative crystallinity ranging from 33.4% for JS to 39.4% for WS. Significant differences were observed in lamellar distance and short-range molecular order characterized by IR ratio of absorbances at 1047/1022cm−1 and full width of half maximum (FWHM) of the band at 480cm−1. WS showed a higher swelling power and a lower close packing concentration at temperatures from 60 to 90°C. The lower peak viscosity of WS was attributed to the formation of less rigid swollen granules at a concentrated regime. WS showed a higher in vitro digestibility compared with IHS and JS.

Late nitrogen application enhances spikelet number in indica hybrid rice (Oryza sativa L.)

To increase rice yield potential, field experiments were conducted in farmers’ paddies in 2011 and 2012 to evaluate the effects of different nitrogen applications on the yield and panicle components of three typical indica hybrid rice varieties in Sichuan Province. The number of grains per panicle resulting from late nitrogen application (LA) was 12 % greater than that obtained from traditional nitrogen application (TA); this increase was the main source of improvements in yield. The number of surviving and differentiated spikelets (NSS and NDiS) resulting from LA was significantly higher than that measured under TA, especially for the Fyou498 cultivar, where the NSS and NDiS increased by 15 % and 14 %, respectively. Compared with TA, the number of degenerated secondary branches and the percentage of degenerated secondary branches (NDeSB and PDeSB) were significantly reduced by 9 % and 11 %, respectively, by LA. This is the first study to demonstrate that an increase in NSS and a decrease in NDeSB lead to yield-improving effects attributable to LA. The grain yields of different varieties ranged from 9225.6 to 9408.7 kg ha−1, the PDeSB was as high as 31 %, and the number of surviving secondary branches (NSSB) was significantly and positively correlated with NSS. These data indicate that the yield of indica hybrid rice has considerable potential for being improved, and increasing NSSB is key to increasing NSS and improving the grain yield. These improvements should be pursued so as to increase the yield of hybrid rice to ensure both food security and sustainable agricultural development.

Impact of Elevated Ozone on Nutrient Uptake and Utilization of Chinese Hybrid Indica Rice (Oryza Sativa) Cultivars under Free-Air Ozone Enrichment

ABSTRACTTo assess the effects of ozone (O3) on uptake and utilization of nitrogen, phosphorus, and potassium nutrients in rice for planning rational fertilization under projected O3 elevation. Two hybrid indica cultivars were exposed to ambient and elevated O3 (E-O3) under a free-air O3 enrichment system. E-O3 differently affected the accumulation and distribution of biomass, and the absorption and distribution of nutrients between cultivars. These effects were related to rice cultivar and nutrient type. E-O3 led to significantly decreased partial factor productivity and grain production efficiency (GPE) of nitrogen in both cultivars; however, the effects of E-O3 on GPEs of phosphorus and potassium varied with cultivar. Responses of nutrients harvest indices between cultivars to E-O3 were adverse. Differences between cultivars and elements should be considered when examining E-O3 potentially affecting the nutrient dynamics for the purpose of reducing the amount of fertilizer applied in paddy systems to decrease potential environmental pollution.

Comparisons of grain yield and nutrient accumulation and translocation in high-yielding japonica/indica hybrids, indica hybrids, and japonica conventional varieties

In China, high-yielding rice varieties called “super rice” have been developed among indica hybrid (IHS), japonica conventional (JCS), and japonica/indica hybrid (JIHS), but yield differences among these three rice groups have not been documented. In this study, four IHS varieties, four JCS varieties, and four JIHS varieties were compared for their yield formation including utilization of nitrogen (N), phosphorus (P), and potassium (K), in field experiments in 2013 and 2014 at Ningbo, Zhejiang, China. The average grain yield of JIHS across varieties and years was 12.4tha−1, 11.3% and 15.3% higher than that of JCS and IHS, respectively. JIHS showed more spikelets per panicle and longer total growth duration compared with JCS and IHS. Compared with JCS and IHS, JIHS showed higher dry matter accumulation after stem elongation and higher leaf area index at heading and maturity stages. The higher grain yield produced by JIHS was accompanied by a higher total N, P, and K accumulation compared with JCS and IHS. Compared with JCS and IHS, JIHS showed higher N translocation from the stem and lower P translocation from the leaf during the period from heading to maturity.

Effects of common Echinochloa varieties on grain yield and grain quality of rice

Barnyard grass, such as Echinochloa crus-galli var. mitis, Echinochloa crus-galli var. zelayensis and Echinochloa colonum, are the main troublesome weeds in rice (Oryza sativa) paddies. This study aimed to investigate the rice yield (quality and quantity) when grown with these common barnyard grass varieties. A 2-year field experiment was conducted using two high-yielding rice cultivars, Liangyoupeijiu (an O. sativa indica hybrid cultivar) and Nanjing 9108 (an O. sativa japonica cultivar) at different developmental stages from transplant to maturity. Treatments included a weed-free (control), rice grown with Echinochloa. crus-galli var. mitis (Ecm), rice grown with E. crus-galli. crusgali var. zelayensis (Ecz), and rice grown with E. colonum (Ec). The results showed that when barnyard grasses were grown with the same rice cultivar, the order of plant height of the three barnyard grass varieties was Ecz>Ecm>Ec, the growth duration was Ecm>Ecz>Ec and the dry matter accumulation of both Ecm and Ecz was greater than Ec. Compared with the weed-free control, there was no significance difference in rice tiller numbers among the treatments within the same rice cultivar. The Ecm and Ecz treatments for both rice cultivars and the Ec treatment of Nanjing 9108 had significantly lower leaf photosynthetic rate, root biomass, root oxidation activity, and dry matter accumulation at both the heading and maturity stages. Lower rice yield loss was detected for all rice grown with barnyard grass, but the loss in yield differed by treatments. Losses in grain yield of rice were 12.7–42.6% in the Ecm treatment, 22.3–55.2% in the Ecz treatment, and 1.5–12.1% in the Ec treatment. For both rice cultivars, Ecm and Ecz treatments had significantly lower grain yield compared with the control. The Ec treatment for Nanjing 9108 had significantly lower grain yield compared to the control, but there was not a significant difference between Ec and the control for Liangyoupeijiu. In general, the japonica cultivar had a greater loss in grain yield compared with the indicia hybrid cultivar under the same treatment. The degree of yield loss by barnyard grass cultivar was Ecz>Ecm>Ec. Grain quality in head rice, chalky kernel, chalky size, and gel consistency was significantly lower for both rice cultivars in the Ecm and Ecz treatments and also for Nanjing 9108 but not for Liangyoupeijiu in the Ec treatment. We conclude that the reduction in leaf photosynthetic rate, root biomass, root oxidation activity at the grain filling stage, and dry matter accumulation at maturity was caused by interference in canopy light transmission caused by barnyard grass and that these factors resulted in losses in grain yield and quality.

Nitrate increases ethylene production and aerenchyma formation in roots of lowland rice plants under water stress.

Ethylene increases root cortical aerenchyma formation in maize (Zea mays L.), rice (Oryza sativa L.) and other species. To further investigate the effects of nitrate, ammonium and water stress on ethylene production and aerenchyma formation in roots, two lowland rice cultivars (Shanyou 63, hybrid indica, and Yangdao 6, inbred indica) were cultured hydroponically with 10% (w/v) polyethylene glycol to simulate water stress. Water stress decreased shoot biomass, stomatal conductivity and leaf water potential in cultivars fed with nitrate but not with ammonium. Water stress induced more aerenchyma formation in cultivars fed with nitrate rather than ammonium, and increased cortical aerenchyma was found in Yangdao 6. Endogenous ethylene production by roots increased significantly under water stress in plants fed with nitrate rather than ammonium. Exogenous ethylene stimulated root cortical aerenchyma formation. Expression of the ethylene biosynthesis gene 1-aminocyclo-propane-1-carboxylic acid (ACC) synthase (ACS5) was greater in roots fed with nitrate rather than ammonium in the presence and absence of water stress. The expression of ethylene signalling pathway genes involved in programmed cell death (lesion-simulating disease (L.S.D.)1.1 and L.S.D.2; enhanced disease susceptibility (EDS) and phytoalexin-deficient (PAD4)) were regulated by the N form and water stress. In plants of cultivars fed with ammonium, L.S.D.1.1 expression increased under water stress, whereas L.S.D.2, EDS and PAD4 expression decreased. In conclusion, nitrate increases ethylene production and cortical aerenchyma formation in roots of water-stressed lowland rice. However, ammonium increased L.S.D.1.1 expression in water-stressed roots, and decreased ACS5, EDS and PAD4 expression, which would inhibit ethylene production and aerenchyma formation.

Combining Ability Analysis of Agronomic Trait in Indica × Indica Hybrid Rice

Combining Ability Analysis of Agronomic Trait in <i>Indica</i> × <i>Indica</i> Hybrid Rice

高产晚稻新组合五优76的选育与应用

五优76系由江西洪崖种业有限责任公司用“五丰A”作母本与自育晚稻强恢复系“R76”配组而成的高产晚籼优质杂交稻组合。该组合株型松散，剑叶宽挺，茎秆粗壮，分蘖力强，穗粒数多，着粒密，结实率较高，千粒重小，产量高，熟期转色中等特点，2017年通过江西省品种审定(赣审稻20170033)。 Wuyou 76 is a high yield and quality late indica hybrid rice combination developed by Jiangxi Hongya seed industry limited liability company (JXHY). It used “Wufeng A” as female parent and a strong restorer line “R76” developed by JXHY as male parent. It is characteristic of loose plant type, wide and straight flag leaf, strong and thick culm, strong tillering ability, large number of grains per panicle, big grain density, higher seed setting rate, small grain weight, high yield and excellent turn color at late growth stage. It was registered and released to commercial produc-tion by Jiangxi Provincial Crop Variety Appraisal Committees in 2017. (Approval Number: Ganshendao 20170033).

Retrospective and perspective on &amp;lt;italic&amp;gt;indica&amp;lt;/italic&amp;gt; three-line hybrid rice breeding research in China

China’s first indica hybrid rice technology has opened up new methods to substantially increase rice yield, tremendously contributing to China’s food security. In this article, we review the discovery of wild abortive male sterility in rice and the history of the development and combination of the male sterile line, maintainer line and restorer line (the “three-line”). With regards to China’s large-scale application of cytoplasmic-nuclear male-sterile (CMS) lines, in addition to the wild-abortive CMS line, there are also Gang, D, Yinshui, dwarf-abortive, Honglian and K types, of which, only the Honglian type exhibits a different restoring and maintaining relationship from that of the wild-abortive line. The diversity of cytoplasmic sterile lines of hybrid rice solves the potential risk in production caused by the use of a single cytoplasmic line. With respect to the breeding of elite parents, the breeding and application of fine male sterile lines, such as Zhenshan 97A, V20A, II-32A and Jin 23A, and fine restorer lines, such as IR24, Minghui 63 and Shuhui 527, were introduced. Currently, the major varieties of China’s three-line hybrid rice have transformed from the high-yielding varieties in the past into the current high-quality, high-yield and disease-resistant varieties. However, three-line hybrid rice faces several problems, such as slow increases of yield potential, low efficiency in genetic improvement of maintainers, the high cost of hybrid rice seed production and the lack of adaptability to the simplified cultivation method. To meet these challenges, it is recommended to establish objectives of breeding new hybrid rice varieties with high quality, high yield, high safety and high efficiency by applying molecular tools to hybrid rice breeding and developing “three-line” hybrid rice parents suitable for mechanized seed production. These would significantly enhance the technological competitiveness of hybrid rice.

Regular Nitrogen Application Increases Nitrogen Utilization Efficiency and Grain Yield in Indica Hybrid Rice

On the basis of research and practical production experience of many years, regular nitrogen fertilizer application (RFA) was used to improve rice (Oryza sativa L.) yield and increase nitrogen utilization efficiency (NUE). Two field experiments (manually transplanted rice with three indica hybrid rice cultivars and four N treatments, mechanically transplanted rice with eight N applications) were conducted in 2011 and 2012, to investigate the effects of RFA on rice yield and NUE. The results showed that RFA increased the total amount of N uptake in the plants and improved NUE when compared with the farmers’ nitrogen fertilizer practices (FFP). The average increment in agronomy efficiency (AE), recovery efficiency (RE), and partial factor productivity for applied nitrogen (PFP) were 12.16, 10.91, and 6.01% for the mechanically transplanted rice and 30.81, 65.57, 6.18% for the manually transplanted rice. The main reason for the increase was the improvement in N concentration of the plant organs. For RFA, the grains per panicle was 12.15 and 7.59% higher than that of FFP, which was the main reason for the 6.19 and 3.33% increase in the yield of the manually and mechanically transplanted rice, respectively. To the best of our knowledge, this is the first RFA strategy to be applied, and the jointing stage and 15 to 20 d after the jointing stage are the key periods for increasing the total amount of N uptake and grain yield; this strategy should be widely applied for indica hybrid rice production.Core Ideas Regular nitrogen fertilizer application significantly increased grains per panicle and then improve rice yield. Regular nitrogen fertilizer application improved plant N concentration and then increased N use efficiency. Jointing stage and 15 to 20 d after jointing stage are the two key stages to apply N fertilizers. Regular N fertilizer application is suitable for both manually and mechanically transplanted rice.

Development of Hybrid Rice Variety FY7206 with Blast Resistance Gene Pid3 and Cold Tolerance Gene Ctb1

Hybrid rice Fanyou 7206 (FY7206), derived from the cross between a sterile line Fanyuan A and a restorer line Fuhui 7206, was bred by the Rice Research Institute, Fujian Academy of Agricultural Sciences, China. FY7206 was characterized by moderate blast resistance, cold tolerance, as well as wide adaptability, and high yields. The blast resistance results indicated that the frequencies of blast races in race B, race C and the total resistance frequency for FY7206 were 95.5%, 100.0% and 97.2%, respectively. The disease resistance results showed that the leaf blast grade for FY7206 was level 1 and panicle blast was level 5. The indoor spray results indicated that FY7206 was resistant to 11 isolates of Magnorpathe oryzae. The blast resistance of FY7206 might be derived from the high expression of blast resistance gene Pid3. The results for simulated cold resistance in an artificial climate chamber indicated that the cold tolerance for FY7206 was moderate at the booting and flowering stages. The cold tolerance results also indicated that FY7206 could be tolerant to temperatures as low as 10°C at the seedling stage. The qRT-PCR results showed that the expression of cold tolerance gene Ctb1 in FY7206 was relatively high. These results suggested that FY7206 is a hybrid indica rice variety with good comprehensive characteristics, including blast resistance and cold tolerance.

Structure and digestion of hybrid Indica rice starch and its biosynthesis

The fine structure (including contents, size and chains length distribution) of amylose and amylopectin of Hybrid Indica Rice starch have an impact on digestion properties of Indica Rice. Indica Rice starches with different amylose contents were chosen as model materials in this study. The amylose and amylopectin size were characterized using size-exclusion chromatography (SEC), the fine structure of amylopectin were studied by flurophore-assisted carbohydrate electrophoresis (FACE) and parameterized by amylopectin biosynthesis model to identify associations with starch digestibility. The digestograms of all starches fit first-order kinetics. All results show that the hybrid Indica rice starch with higher amylose content has a slower digestion rate. SEC results show that there is no obviously in chains length distribution (CLD) for amylopectin, but a significantly sharp difference in amylose. No difference in amylopectin was also observed from FACE result. The amylose starch controlled by GBSSI enzyme may be the key parameter to influence starch digestion.

Quality and Field Growth Characteristics of Hydroponically Grown Long‐Mat Seedlings

Looming labor shortages and lower efficiency demand a shift from the cultivation of seedlings via the traditional nutritive soil method (CK) to hydroponically grown long‐mat seedlings (HLMS), a new method of raising rice (Oriza sativa L.) seedlings. This study was conducted to investigate the seedling quality and field growth characteristics of HLMS. We examined the effect of HLMS on seedling quality, mechanical transplantation quality, field growth characteristics, yield and benefit/cost ratio compared with those of CK (as a control). A widely grown conventional japonica rice cultivar (Wuyunjing24) and an indica hybrid rice cultivar (6Liangyou9368) were used as test material. The HLMS and CK showed no significant differences in weight/height ratio, seedling emergence rate, N content of leaves or antioxidant enzyme activities after transplantation; however, HLMS exhibited a more vigorous root system, a significantly decreased leaf area index and an extended transplantation period. The mechanical transplantation quality of HLMS was similar to that of CK but showed a significantly improved force of root entanglement. Compared with CK, the dry matter accumulation of HLMS differed quite low at the early field growth stage, whereas increased rapidly at the late growth stage. The yield and benefit/cost ratio of HLMS were equivalent or superior to those of CK. Briefly, the seedling quality of HLMS was better than that of the control, and its mechanical transplantation quality was comparable to that of the CK, enabling high‐yield and high‐efficiency rice production.Core Ideas Hydroponically grown long‐mat rice seedlings is a novel seedling cultivation method that reduces labor costs and improves efficiency. The force of root entanglement of hydroponically grown long‐mat rice seedlings was significantly improved. The yield and benefit/cost ratio of hydroponically grown long‐mat rice seedlings were equivalent or superior to those of the control.

Transgenic restorer rice line T1c-19 with stacked cry1C*/bar genes has low weediness potential without selection pressure

Stacked (insect and herbicide resistant) transgenic rice T1c-19 with cry1C*/bar genes, its receptor rice Minghui 63 (herein MH63) and a local two-line hybrid indica rice Fengliangyou Xiang 1 (used as a control) were compared for agronomic performance under field conditions without the relevant selection pressures. Agronomic traits (plant height, tiller number, and aboveground dry biomass), reproductive ability (pollen viability, panicle length, and filled grain number of main panicles, seed set, and grain yield), and weediness characteristics (seed shattering, seed overwintering ability, and volunteer seedling recruitment) were used to assess the potential weediness without selection pressure of stacked transgene rice T1c-19. In wet direct-seeded and transplanted rice fields, T1c-19 and its receptor MH63 performed similarly regarding vegetative growth and reproductive ability, but both of them were significantly inferior to the control. T1c-19 did not display weed characteristics; it had weak overwintering ability, low seed shattering and failed to establish volunteers. Exogenous insect and herbicide resistance genes did not confer competitive advantage to transgenic rice T1c-19 grown in the field without the relevant selection pressures.

Effects of Silicon Fertilizer Rate on Grain Yield and Related morphological and Physiological Characteristics in Super Rice of Yongyou Japonica / indica Hybrids Series

Effects of Silicon Fertilizer Rate on Grain Yield and Related morphological and Physiological Characteristics in Super Rice of Yongyou <i>Japonica</i> / <i>indica</i> Hybrids Series

Effects of Alternate Wetting and Drying Irrigation on Yield and Water Use Efficiency of Rice

Alternate wetting and drying (AWD) irrigation has been widely adopted to replace conventional irrigation (CI) for saving water and increasing water use efficiency (WUE) in irrigated rice systems in China. However, there is limited information about how AWD affects yield, WUE, and root and shoot growth and development. To fill this knowledge gap, we conducted the experiment using three local high-yielding rice cultivars, Wuyunjing 24 (japonica), Yangliangyou 6 (two-line indica hybrid rice), and Yongyou 2640 (three-line indica/japonica hybrid rice) under the two water managements, CI and AWD, during the whole growing season. The results showed that, when compared with CI, AWD increased grain yield by 5.34%, 5.85%, and 6.62% and WUE by 28.9%, 25.3%, and 27.6%, respectively which mainly attributed to greater root oxidation activity, amount of root bleeding sap, content of cytokinins (zeatin + zeatin riboside) in roots and leaves, highten photosynthetic rate of flag leaf, deeper root distribution, increased productive tillers and leaf area, and enhanced activities of enzymes involved in sucrose-to-starch conversion in grains during grain filling. The results demonstrate that AWD is an effective practice to increase grain yield and water use efficiency through enhancing root and shoot growth and development.