Super High-yielding Rice Research Articles

DWARF AND LESS TILLERS ON CHROMOSOME 3 promotes tillering in rice by sustaining FLORAL ORGAN NUMBER 1 expression.

Three key factors determine yield in rice (Oryza sativa): panicle number, grain number, and grain weight. Panicle number is strongly associated with tiller number. Although many genes regulating tillering have been identified, whether Dof proteins are involved in controlling plant architecture remains unknown. The dwarf and less tillers on chromosome 3 (dlt3) rice mutant produces fewer tillers than the wild type. We cloned DLT3, which encodes a Dof protein that interacts with MONOCULM 3 (MOC3) in vivo and in vitro and recruits MOC1, forming a DLT3-MOC3-MOC1 complex. DLT3 binds to the promoter of FLORAL ORGAN NUMBER 1 (FON1) to activate its transcription and positively regulate tiller number. The overexpression of MOC1, MOC3, or FON1 in the dlt3 mutant increased tiller number. Collectively, these results suggest a model in which DLT3 regulates tiller number by maintaining the expression of MOC1, MOC3, and FON1. We discovered that DLT3 underwent directional selection in the Xian/indica and Geng/japonica populations during rice domestication. To provide genetic resources for breeding varieties with optimal panicle numbers, we performed large-scale diversity sequencing of the 1,080-bp DLT3 coding region of 531 accessions from different countries and regions. Haplotype analysis showed that the superior haplotype, DLT3H1, produced the most tillers, while haplotype DLT3H6 produced the fewest tillers. Our study provides important germplasm resources for breeding super high-yielding rice varieties with combinations of superior haplotypes in different target genes, which will help overcome the challenge of food and nutritional security in the future.

Yield Gap Analysis of Super High-Yielding Rice (>15 t ha−1) in Two Ecological Regions

Super high-yielding rice (SHYR) (>15 t ha−1) plays a crucial role in global food production and security. We hypothesized that the external environment of different ecological regions could improve biomass accumulation in different periods and thus increase the rice yield. Two SHYR varieties, i.e., Xiangliangyou900 (XLY900) and Yliangyou900 (YLY900), were cultivated in the YONGSHENG and LONGHUI ecoregions, China. The results indicated that the average yield of the two SHYRs in the LONGHUI ecological region was 15.27–15.45 t ha−1 and 18.81–20.10 t ha−1 in YONGSHENG. The high grain yield in the YONGSHENG ecoregion was mainly due to the increased number of spikelets per panicle, crop growth rate, and total biomass during the transplanting–heading stage (TP-HS) and heading–maturity stage (HS-MS), and harvest index. The yield of SHYR was significantly correlated with external environment conditions, i.e., average minimum temperature, average daytime, and night-time temperature, and average daily temperature at the TP-HS, HS-MS, and transplanting–maturity (TP-MS) stages. The rice yield was significantly and positively correlated with the cumulative daily radiation. Therefore, it can be concluded that the final yield of super high-yield rice is closely related to the utilization of temperature and radiation resources during the growth process in the ecological environment.

Differences and mechanisms of post-anthesis dry matter accumulation in rice varieties with different yield levels

Post-anthesis dry matter accumulation (PDMA) plays an important role in yield, but the differences and mechanisms of PDMA among rice varieties with different yield levels are still unclear. Field experiments were conducted using six rice varieties with medium, high, and super high yield levels selected to not only analyze the relationship between PDMA and yield but also compare the physiological indexes among different varieties. The effects of grain fertilizer on PDMA and yield were also observed. PDMA and apparent transferred mass of non-structural carbohydrate (NSC) in stems from heading to maturity were significantly positively correlated with yield. The physiological indexes (root oxidation activity, zeatin ​+ ​zeatin riboside contents in roots and leaves, and leaf photosynthetic rate) at 0–20 days after anthesis (DAA) of super high-yielding varieties were significantly higher than those of medium-yielding and high-yielding varieties. In addition, the α-amylase activity in stems at 30–50 DAA of super high-yielding varieties was significantly higher than other varieties. Compared with no grain fertilizer application rate (GFAR), the GFAR for maximum yield and yield increase of super high-yielding varieties were higher than other varieties. The above physiological indexes at 10–20 DAA were increased under GFAR at 54 ​kg ​ha−1. The α-amylase activity at 30–50 DAA was inhibited under GFAR at 81 ​kg ​ha−1 that hindered NSC translocation, resulting in decreased yield. Our results indicated that higher PDMA and NSC translocation were the crucial characteristics that benefited the yield formation of super high-yielding rice varieties.

Effects of root morphology and physiology on the formation and regulation of large panicles in rice

Abstract At present, indica/japonica hybrid rice varieties of the Yongyou series generally show high yield and large panicles, but the physiological mechanism on the formation of large panicles is not clear. It is of great significance to understand the physiological mechanism and regulation of the formation of large panicles in super high-yield rice varieties. In this study, five groups of different rice varieties with significant differences in yield levels were selected as materials to study the contribution of large panicles to rice yield, the physiological changes in roots and canopy during the panicle differentiation stage and the regulation of large panicles by panicle nitrogen fertilizer under field and pot cultivation conditions. The results showed that 1. high-yield indica/japonica hybrid rice varieties were characterized by high spikelet number per panicle and high total number of spikelets. 2. The zeatin (Z) and zeatin riboside (ZR) contents in roots and panicles from spikelet primordium differentiation (SPD) to pistil and stamen formation (PSF), root activity (root dry weight, root oxidation activity, root bleeding rate, root total absorbing surface area and root active absorbing surface area) and non-structural carbohydrate (NSC) accumulation in stems from pollen mother cell meiosis (PMC) to pollen filling (PF) were very significantly and positively correlated with spikelet number per panicle. 3. Compared with 0 N (no panicle nitrogen fertilizer), the number of spikelets per panicle and total spikelets of Yangdao 6 and Yongyou 1540, the Z + ZR contents in panicles and roots during SPD-PSF, and the root activity and NSC accumulation in stems during PMC-PF were significantly improved under LN (panicle nitrogen fertilizer at a rate of 1.2 g pot-1) and MN (panicle nitrogen fertilizer at a rate of 2.4 g pot-1). High Z + ZR contents in young panicles and roots during SPD-PSF and large amounts of root activity (root dry weight, root oxidation activity, root bleeding rate, root total absorbing surface area and root active absorbing surface area) and NSC accumulation in stems during PMC-PF were important physiological factors in the formation of large panicles in super high-yield indica/japonica hybrid rice. Improvements in the above indexes during the panicle differentiation stage are likely contribute to the formation of large panicles and the increase in rice yield.

온도상승에 따른 논 제초제의 약효 및 약해 변동

본 연구는 기후변화로 인한 온도가 상승할 경우 현재 국내에서 널리 사용되어 지고 있는 되어 지고 있는 HPPD 저해 제초제에 대한 주요 벼 품종들의 약해와 논 잡초들의 약효 변동정도를 구명하기 위하여 실시하였다. 온도가 높을수록 벼의 약해정도는 높게 나타났으며, 줄기보다 뿌리에서 약해정도가 더 심하게 나타났다. 대기온도 보다 약 <TEX>$3^{\circ}C$</TEX> 높은 비닐하우스 조건에서 일반계 밥쌀용 자포니카 벼 품종들은 회복할 정도로 약해 경미하게 발생하였다. 그러나 찰벼, 초다수성벼, 통일벼 품종들은 수량이 감소될 정도로 약해가 발생하였다. 인공기상실 조건에서 일반계 밥쌀용 자포니카 벼 품종의 약해는 품종에 따라 차이가 있으나 고온조건인 <TEX>$27.5^{\circ}C$</TEX>에서 4-8로 생육이 심하게 억제되었거나 고사하였다. 그러나 찰벼와 통일벼 품종들은 <TEX>$25^{\circ}C$</TEX> 이상에서 약해가 심각하게 발생하였으며, 통일계 품종인 남천은 <TEX>$27.5^{\circ}C$</TEX>에서 완전히 고사하였다. 논에서 이앙시기별 벼 약해실험에서 밥쌀용 자포니카 품종인 신동진벼는 6월5일(평균온도 <TEX>$22.1^{\circ}C$</TEX>) 및 6월15일(평균온도 <TEX>$22.5^{\circ}C$</TEX>)에 이앙한 논에서 약해는 경미하게 발생하였다. 그러나 6월30일 이앙(평균온도 <TEX>$25.2^{\circ}C$</TEX>)한 논에서는 약해가 3이상이었고, 고온인 7월15일에 이앙(평균온도 <TEX>$27.9^{\circ}C$</TEX>)한 논에서는 벼가 뚜렷한 억제현상을 보였다. 온도조건을 달리한 인공기상실에서 benzobicyclon+mefenacet+phenoxsulam액상수화제에 대한 물달개비, 올챙이고랭이, 올방개의 방제효과는 약제 처리 후 25일에 90% 이상의 높은 효과를 보였다. 그러나 강피의 방제효과는 <TEX>$25^{\circ}C$</TEX>까지는 95% 이상의 방제효과를 보였으나 고온조건인 <TEX>$27.5^{\circ}C$</TEX>에서는 40%의 낮은 방제효과를 보였다. 이앙시기가 서로 다른 논에서는 잡초발생량은 6월 30일 이후 이앙 논에서는 현저히 감소하였다. 일년생 잡초들인 물달개비, 올챙이고랭이, 여뀌바늘은 이앙시기에 관계없이 90% 이상의 높은 방제효과를 보였다. 그러나 강피는 7월15일 이앙(평균온도 <TEX>$27.9^{\circ}C$</TEX>)한 논에서 방제효과가 다른 이앙시기에 비하여 상대적으로 낮은 73% 방제효과를 보였다. 다년생 잡초 올방개는 온도가 상승함에 따라 약효가 감소하는 것으로 나타나 인공기상실에서 조사된 결과와는 차이가 있었다. 따라서 기후변화로 인한 대기의 온도가 상승할 경우 제초제에 대한 벼의 약해가 발생할 가능성이 높다. 논에서는 우점잡초 변화가 예상되고, 일년생 잡초들 중에서 물달개비 및 올챙이고랭는 온도상승으로 제초제 약효에 크게 영향을 받지 않으나 강피는 약 <TEX>$27^{\circ}C$</TEX>에서 방제효과가 저조하게 나타났다. This study was conducted to investigate the phytotoxicity of main rice varieties and control efficacy of HPPD inhibitor to major paddy weeds at the time of temperature rise due to climate change. Phytotoxicity of herbicide to rice was increased as temperature was increased, and more severe in root than shoot. The phytotoxicity of japonica rice cultivars for the rice were mild enough to recover. However, glutinous rice, super high yield rice, and Tongil rice varieties were damaged enough to decrease the yield. Shindongjinbyeo transplanted by June 15, showed phytotoxicity enough to recover. However, in the rice field on June 30 and on July 15, the rice showed a remarkable inhibition. The control effect of Monochoria vaginalis and Scirpus juncoides was more than 90% under the temperature condition controlled artificially. However, Echinochloa oryzicola was controlled 40% at <TEX>$27.5^{\circ}C$</TEX>, which is a high temperature condition. In rice fields with different transplanting times, annual weeds except for E. oryzicola were highly controlled by 90% or more regardless of the time of transplanting.

Tillering Characteristics and Its Relationship with Population Productivity of Super-high Yield Rice Population of Yongyou 12

We comparatively studied tillering and panicle formation characteristics of super-high and high yield populations formed by the regulation of cultivation measures using indica-japonica super rice Yongyou 12 transplanted by seedlings with tillers at the age of four leaves with one leaf bud. The results showed that yield from tillers and its contribution rate to total yield were 11.53 t ha–1 and 87.77% for super-high yield population, and 10.59 t ha–1 and 87.40% for high yield population. Super-high yield population had higher yield from primary and secondary tillers which were the major part contributed to total yield, the contribution rate to total yield of primary tillers for super-high yield population was slightly lower than that for high yield group, while that of secondary tillers, the contribution rate to total yield was higher in super-high yield population than in high yield population. For super-high yield population, the primary tillers emerged from leaf 1 to leaf 9 on main stem, among them the tillers from leaf 4 to leaf 7 had higher emerging rate and more panicles, secondary tillers emerged and earbeared mainly in 1/3, 2/3, 3/3, 2/4, 1/5. High yield population had higher emerging rate of triple tillers but lower panicle rate than super-high yield population, its primary tillers emerged and earbeared mainly in 4/0 to 7/0 while in the secondary tillers 1/3, 2/3, 3/3. Super-high yield population had higher mean values in panicle length, panicle weight, total grain number and grain density than high yield population, but seed-setting rate was slightly lower.

Yield Potential of High-Yield Rice Varieties in the Tohoku Region of Japan

To achieve a super high brown rice yield exceeding 10 t ha -1 in the Tohoku region (relatively cold), a two-year field experiment was conducted. The yield components, morphological traits and dry matter production among the Japonica type high-yield variety “Fukuhibiki,” indica type high-yield variety “Takanari,” large grain type high-yield variety “Bekoaoba” and two conventional Japonica type varieties were compared. Although the traits relating to high yield varied greatly, the three high-yield varieties all showed a large sink size, heavy rice yield at 30 days after heading (30 DAH) and a high harvest index. The effects of nitrogen application and planting density on the morphological traits, dry matter production and yield in the large grain type variety Bekoaoba were investigated. Although high nitrogen application (HN) increased the brown rice yield from 8 to 9.5 t ha -1 , regulation of the timing of topdressing and/or planting density under HN could not increase the brown rice yield beyond 10 t ha -1 . Strategies to achieve a super high-yield rice in the Tohoku region were discussed.

Effects of Nitrogen Application and Planting Density on Morphological Traits, Dry Matter Production and Yield of Large Grain Type Rice Variety Bekoaoba and Strategies for Super High-Yielding Rice in the Tohoku Region of Japan

To achieve super high yield of more than 10 t ha-1 in the Tohoku region (colder area of Japan), we conducted a two-year field experiment using a large grain type high-yielding rice variety Bekoaoba. Although high nitrogen application (HN) increased the top dry weight at the full heading stage only slightly, it increased the sink size (single grain weight x the number of spikelets per area), leaf area index and nitrogen content at the full heading stage and accordingly the dry matter production during the ripening period. As a result, the gross hulled rice yield was higher under HN than under standard nitrogen application (SN). Under HN, early topdressing increased not only the number of differentiated spikelets but also the number of degenerated spikelets. As a result, the sink size and gross hulled rice yield of the plants were not changed by the early topdressing. Under HN, the higher planting density increased the number of panicles per area but decreased the number of spikelets per panicle. As a result, the sink size and gross hulled rice yield were not changed with the planting density. In conclusion, HN produced the gross hulled rice yield of more than 9 t ha-1. However, the gross hulled rice yield could not be increased more than 10 t ha-1 by regulation of the timing of topdressing and /or the planting density. We discussed the strategies for super high-yielding rice in the Tohoku region.

Analysis of quantitative trait loci for panicle layer uniformity in rice (Oryza sativaL.)

Uniformity in the height of main stem and tillers is a key factor affecting ideal plant type, a key component in super high-yielding rice breeding. An understanding of the genetic basis of the panicle layer uniformity may thus contribute to breeding varieties with good plant type and high yield. In the present study, a doubled haploid (DH) population, derived from a cross between indica rice variety Zhai-Ye-Qing 8 (ZYQ8) and japonica rice variety Jing-Xi 17 (JX17) was used to analyze quantitative trait loci (QTL) for panicle layer uniformity related traits. Six, four and three QTL were detected for the highest panicle height (HPH), lowest panicle height (LPH) and panicle layer dis-uniformity (PLD), respectively. qHPH-1-1 and qPLD-1 were located at the same interval on chromosome 1. The JX17 allele(s) of these QTL increased HPH and PLD by 2.57 and 1.26 cm, respectively. Similarly, qPLD-7 and qHPH-7 were located at the same interval on chromosome 7, where the ZYQ8 allele(s) increased HPH and PLD by 3.74 and 1.96 cm, respectively. These four QTL were unfavourable for panicle layer uniformity improvement because a decrease of the PLD was accompanied by decrease of the plant height. qPLD-6 and qLPH-6-1 were located at the same interval on chromosome 6, however here the JX17 allele(s) increased LPH, but decreased PLD, suggesting that this QTL was favourable for improvement of panicle layer uniformity. The markers identified in this study are potential for marker assisted breeding for the improvement of the panicle layer uniformity and ideal plant type.

Population Characteristics of Super &lt;I&gt;Japonica&lt;/I&gt; Rice Ningjing 1 and Ningjing 3 and Its Responses to Nitrogen

In order to study the super high-yielding population characteristics of super japonica rice and its responses to nitrogen, two field experiments with five N rate treatments and four N application ratio treatments of Ningjing 3 were carried out in 2008, the 6.7 ha demonstration fields of Ningjing 1 and Ningjing 3 in 2007 and 2008 were also investigated. Results showed that the dry matter accumulation of Ningjing 1 and Ningjing 3 after heading was 70–80% of the grain yield, and the apparent translocation ratio of dry matter from stem and leaves to grain was small, which resulted in the high and stable grain yield. Ample spikelets per square meter were the guarantee of super and stable high yield. To achieve the target yield of 11.0 t ha?1, the spikelets per square meter must be above 42 000 m?2; to achieve the target yield of 11.7 t ha?1, the spikelets per square meter must be above 45 000 m?2, as well as grain filling rate and grain weight must be above 90% and 26 mg. For super high-yielding rice population, the op- timal LAI at heading should be 7.0–7.5, crop growth rate (CGR) from heading to maturity should be higher and the harvest index (HI) should be above 0.5. The appropriate N rate and relative more N topdressed at panicle initiation stage could not only ensure the optimal LAI at heading, but also maintain the plant type characteristics of super high-yielding rice, improve the LAI after heading, leaf area duration, CGR and HI, therefore achieve the super high grain yield.

超多収水稲生産システムのLCA：地球温暖化への影響およびエネルギー投入量による慣行システムとの比較

Objective. The purpose of this paper is to conduct comparative life cycle assessment of super high-yield and conventional rice production systems. Since super high-yield rice production needs further energy and resource inputs as compared with the conventional production, the judgment of relative superiority should be based on the assessment of whole systems. Therefore, life-cycle energy use and life-cycle CO2 emissions are used for the comparison.Results and Discussion. Super high-yield rice production consumes much more fuels than conventional production due to drying of the unhulled rice and fertilizer production, and thus it needs much more energy inputs and emit much more greenhouse gases than the conventional production if we use the functional unit of unit area. Energy inputs per ha were 44 GJ for the super high-yield rice production and 42 GJ for conventional production. GHG emissions per ha were 8.0 t CO2 eq. for the super high-yield rice production and 7.5 t CO2 eq. for the conventional production. However, if we utilize the functional unit of 1 kg of brown rice, we have another result as follows: energy inputs per 1 kg of brown rice were 5.46 MJ for the super high-yield rice production and 7.70 MJ for the conventional production; GHG emissions per 1 kg of brown rice was 1.00 kg CO2 eq. for the super high-yield rice production, and 1.39 kg CO2 eq. for the conventional production. That is, energy inputs and GHG emissions per 1kg of brown rice for the super high-yield rice production were lesser than conventional production. The breakdown of the environmental impacts showed that the production of agricultural machines, materials, fertilizer, agrochemicals and fuels accounts for more than 70 % of all energy inputs. This means that the extension of the lifetime of machines and materials and the reduction of fertilizers and pesticides are effective in reducing energy inputs. In addition, since energy inputs to the drying of the unhulled rice were comparatively large, the reduction of the fuel consumption for drying will be important.Conclusions. This study clarified the environment load of super high-yield and conventional rice production systems. Improving rice yields was considered to be an effective way in decreasing energy inputs and GHG emissions per 1kg of brown rice. It was shown that we should use the inventory data of rice production for energy in LCA of the biofuel production.

Photosynthetic Functions of Different Senescing Leaves in the Canopy of Super high-yield Rice &amp;lsquo;Hua-An3&amp;rsquo;

In order to improve rice yields to feed a growing population, China has carried out a `Super High-Yield Rice Project' since 1996. Tremendous progress was made during the `Ninth Five-Year Plan' and several new varieties of rice hybrids were released. `Hua-an 3' (`X07S'×`Zihui100') is a new high yield variety that has yields of more than 10 500 kg·hm -2; this compares with yields of 7 500-8 500 kg·hm -2 in the traditional hybrid rice `Shanyou 63' (`Zhenshan 97A'×`Minghui 63'). The photosynthetic functions and pigments of the upper most 5 senescing leaves of the canopy of `Hua-an 3' were studied by techniques of fluorescence induction kinetics, low temperature (77K) fluorescence emission spectrum and HPLC. The results showed that the maximal quantum yield of PSⅡ photochemistry (F v/F m), efficiency of excitation energy captured by open PSⅡ reaction centers (F v′/F m′), quantum yield of PSⅡ electron transport (Φ PSⅡ), photochemical quenching coefficient (qP), and the content of photosynthetic pigments, especially chlorophyll (Chl), neoxanthin (N), lutein (L) and β-carotene (β-Car), of the flag leaf were higher than those of other leaves but its excitation pressure (1-qP) was lower. It was shown that the content of the core antenna complex CP47 in photosystemⅡ (PSⅡ) and photosystem Ⅰ (PS Ⅰ) of the flag leaf also was higher than in other leaves, but the content of its non-active aggregate of light harvesting complex in PSⅡ (LHCⅡ) derived from the Gaussian analysis of low-temperature (77K) fluorescence emission spectra was lower than that of the other leaves. Our research results are as follows: 1) at later growth and development stages of rice, the dry matter of grain was mainly provided by most photosynthesis occurred in the uppermost 3 leaves in the canopy; 2) in the course of leaf senescence, the senescence of photosynthetic reaction centers was quicker than that of the antenna system; 3) one of the photoprotective pathways in hybrid rice may be through an increase in the content of PS Ⅰ, absorption of more light energy, and stimulating a high speed electron transport cycle in order to protect the photosynthetic apparatus under photoinhibitory conditions; 4) in the course of leaf senescence of rice, partial chlorophyll b was probably reduced to chlorophyll a, to decrease the content of LHCⅡ, thus reducing the amount of energy absorbed by LHCⅡ and decreasing the amount of photoinhibitory damage.

Relationship between leaf photosynthetic function at grain filling stage and yield in super high-yielding hybrid rice (Oryza sativa. L)

The characteristics of dry matter production before and after heading and the relationships between photosynthesis of flag leaves and dry matter accumulation in panicles were investigated on super high-yielding rice cv. Xieyou 9308 (the yield of up to 12 t/ha) with rice cv. Xieyou 63 as a control. The results showed that (i) the capacity of dry matter production before and after heading in Xieyou 9308, i.e. biomass and daily dry matter production, was remarkably higher than that in Xieyou 63, especially after heading; (ii) CO(2) assimilation capacity in flag leaves in Xieyou 9308, namely Leaf Source Capacity (LSC), was also significantly higher than that in Xieyou 63, and the supply of photosynthate in leaves and the demand of grain filling were completely synchronous in Xieyou 9308, but photosynthetic function in flag leaves in Xieyou 63 declined sharply 20 days after heading and it was not enough to meet the demand of grain filling. These results confirmed that high efficient photosynthetic function in leaves after heading and its complete synchronization with grain filling are the key approaches to super high yield of rice.

Characterization of photosynthesis, photoinhibition and the activities of C4 pathway enzymes in a superhigh-yield rice, Liangyoupeijiu

Characteristics of photosynthetic gas exchange, photoinhibition and C(4) pathway enzyme activities in both flag leaves and lemma were compared between a superhigh-yield rice (Oryza sativa L.) hybrid, Liangyoupeijiu and a traditional rice hybrid, Shanyou63. Liangyoupeijiu had a similar light saturated assimilation rate (Asat) to Shanyou63, but a much higher apparent quantum yield (AQY), carboxylation efficiency (CE) and quantum yield of CO(2) fixation (PhiCO(2)). Liangyoupeijiu also showed a higher resistance to photoinhibition and higher non-radiative energy dissipation associated with the xanthophyll cycle than Shanyou63 when subjected to strong light. In addition, Liangyoupeijiu had higher activities of the C(4) pathway enzymes in both flag leaves and lemmas than Shanyou63. These results indicate that higher light and CO(2) use efficiency, higher resistance to photoinhibition and C(4) pathway in both flag leaf and lemma may contribute to the higher yield of the superhigh-yield rice hybrid, Liangyoupeijiu.

Crossing Rice Strains to Keep Asia's Rice Bowls Brimming

FUTURE FOODBEIJING, CHINA-- While plant breeders in most of the world fear that grain yields are plateauing ([see main text][1]), a Chinese plant breeder says he is on the verge of creating a superhigh-yield rice hybrid that promises jumps of 15% to 20% in potential yields over existing hybrids. [1]: http://www.sciencemag.org/cgi/content/short/283/5400/310