Rice Yield Potential Research Articles

Greenhouse gas emissions reduction and rice yield potential under bio-fertilizer application

Rice cultivation is one of the largest contributors of CH4 emission to the atmosphere. It contributes approximately 5 to 19% of the total global CH4 emissions. The aim of this research was to investigate the effect of using of bio-fertilizers on greenhouse gas (GHG) emissions and rice yield. The experiment was conducted from September 2016 to January 2017 in experimental station of Indonesian Agricultural Environmental Research Institute, Pati Central Java. This experiment used completely randomized design with three treatments and five replications. The treatments were (1) no amendments (control), (2) rice straw 3 t ha−1 and (3) rice straw 3 t ha−1 + bio-fertilizer 10 L ha−1. The CH4, CO2, and N2O gas fluxes were measured weekly during the rice-growing season by using closed chamber method. The results of this study showed that application of straw + bio-fertilizers treatment reduced GHG emissions of CH4, N2O, and CO2 by 9.2, 14.78, and 27.68%, respectively compared to the application of straw treatment. The application of straw + bio-fertilizers treatment decreased global warming potential (GWP) by 10.75% compared to the application of straw. The GHG index (GHGI) of straw + bio-fertilizer treatment decreased 8.27% compare to control. The results suggested that application of bio-fertilizer could support environmentally agriculture in supporting food self-sufficiency.

Evaluation of alleles at OsAGPS2, OsAGPL2, and OsSUT1 related to grain filling in rice in a common genetic background

AbstractPoor grain filling, characterized by incidence of partially filled grain, is one of the major problems to be improved for maximizing the yield potential in rice (Oryza sativa L.) cultivars with numerous spikelets in a panicle (extra‐heavy panicle type [EHPT]). This study evaluated the grain‐filling‐related alleles at APS2 and APL2, the loci for the small and large subunits of ADP‐glucose pyrophosphorylase (AGPase), respectively, and at SUT1, sucrose transporter, for their effects and interactions on grain filling and associated traits of EHPT cultivars. Two sets of derived lines were developed. Each of these lines was one of the eight possible homozygotes of alleles derived from rice cultivars Akenohoshi and Milyang 23 at the three loci in nearly common genetic backgrounds. They were examined for grain‐filling traits in two different years. Results showed that APL2‐2, and SUT1‐2 in part, derived from Milyang 23 showing relatively good grain filling, significantly improved grain filling compared with APL2‐1 and SUT1‐1 from Akenohoshi showing poor filling. This improvement in grain filling may result from increased AGPase activity and expression of APL2 and SUT1 proteins, by means of APL2‐2 and SUT1‐2. However, the variations in AGPase activity, protein expression, and the degree of grain filling were not associated with the gene expression of the three loci, implying post‐transcriptional regulation. These results strongly suggested that APL2‐2 and SUT1‐2 are associated with good grain filling.

Effects of climate change on the yield potentials and resource use efficiencies of mid-season indica rice cultivars in Eastern China

Abstract Global climate change affects crop yields and endangers food security. High yielding rice varieties adapted to climatic changes is a key breeding objective. However, little is known regarding the impact of climate change on the yield potentials and resource utilization efficiencies of modern rice cultivars in Eastern China. Using two-year field experiment, we investigated the biomass, nitrogen (N) uptake, and yield in relation to climatic resource use efficiencies of eight representative Chinese mid-season indica rice (Oryza sativa L.) cultivars grown in the Middle-Lower Yangtze Area over the last fifty years. The yield potential of rice from 1961–2015 was simulated using the ORYZA (v3) model. The total thermal time (growing degree days) increased at a rate of 3.3 ℃ yr−1, while sunshine hours decreased at a rate of 2.4 h yr−1 over the past five decades during growth period. Compared with the average potential yield from 1961 to 1975, an average 5.65 % of reduction occurred across different cultivars from 2001 to 2015. However, the rice potential yield increased by 52.0 kg ha−1 yr−1 in the released cultivars with increasing years of release. The use efficiencies of sunshine hours and thermal time for the cultivar Yangliangyou6 released in 2001 increased by 68.5 % and 59.5 % compared with the cultivar Shenglixian released in 1938. The increase of potential yield in the released cultivar Yangliangyou6 was attributed to increase utilization efficiency of radiation. Modern cultivars (semi-dwarf and super rice) maintained greater leaf area index (LAI) during the filling period without modification in photosynthetic rate. Besides, the decrease in grain N concentration contributed to stay-green characteristic and to the efficient use of N in modern cultivars. Thus, modern indica rice cultivars tolerate the adverse climatic changes by optimizing plant productivity and increasing resource utilization efficiencies.

Inheritance of some flag leaf and yield characteristics by half-diallel analysis in rice crops (Oryza Sativa L.)

This study was conducted during 2018 and 2019 at the Rice Research and Training Centre farm, Sakha, Kafr el Sheikh, Egypt. Six genotypes of rice, Sakha 101, Giza 178, Irat 170, Wab-56-104, IR65500-127 and IR69853 were half-diallel crossed to estimate the combining ability effect as well as sink and yield potential in rice. Sink capacity (number of spikelets/panicle and 1000-grain weight), source leaf (flag leaf length, flag leaf width and flag leaf area), source-sink association (number of spikelets/panicle to flag leaf area ratio) and traits of yield components (filled grains number/panicle and panicle number) plant and grain yield/plant) were analysed. The results indicated that both general and specific combining ability were highly significant for all the studied characteristics. IR65500-127, Giza 178, and Sakha 101 were identified as good parents, so these parents were suggested for a further recombinant breeding programme. The cross of 3 × 5 was found to be superior for flag leaf width and grain yield, while the cross of 1 × 4 was found to be superior for flag leaf length, flag leaf length/width ratio, chlorophyll content and number of panicles/plant. Advancing these crosses and effected selections in segregating generation would be helpful to develop high yielding varieties. The genetic parameter showed a dominant deviation in one direction was controlled for all characters except flag leaf length. The analysis of the regression line showed that the over-dominance played an important role in the inheritance of gene action for grain yield/plant.

Ghd7 is a negative regulator of zinc concentration in brown rice

Zinc (Zn) is an essential micronutrient for human, and improving Zn concentration in rice could be a simple and effective way to solve insufficient Zn uptake from daily diet. In this study, a recombinant inbred line (RIL) population was developed from a commercial hybrid combination Wandao153, and subjected to quantitative trait loci (QTL) detection for Zn concentration in brown rice and heading date. Five QTL for Zn concentration and six for heading date were detected across 2 years, among which two QTL for Zn concentration and two for heading date were co-located on chromosome 7 and 8, respectively. The two co-located QTL on chromosome 7, qZn7 and qHd7, were likely to be Ghd7, a major gene for heading date and yield potential in rice. A combination of Zn concentration analysis and haplotype analysis of three pairs of genetic materials for Ghd7 revealed that it is a negative regulator of Zn concentration in brown rice. The other two co-located QTL on chromosome 8, qZn8 and qHd8, were likely to be Ghd8/DTH8, another major gene for heading date and yield potential in rice. These results could be of great use in genetic improvement of Zn concentration in brown rice.

Phytohormone-Mediated Molecular Mechanisms Involving Multiple Genes and QTL Govern Grain Number in Rice.

Increasing the grain number is the most direct route toward enhancing the grain yield in cereals. In rice, grain number can be amplified through increasing the shoot branching (tillering), panicle branching, panicle length, and seed set percentage. Phytohormones have been conclusively shown to control the above characteristics by regulating molecular factors and their cross-interactions. The dynamic equilibrium of cytokinin levels in both shoot and inflorescence meristems, maintained by the regulation of its biosynthesis, activation, and degradation, determines the tillering and panicle branching, respectively. Auxins and gibberellins are known broadly to repress the axillary meristems, while jasmonic acid is implicated in the determination of reproductive meristem formation. The balance of auxin, gibberellin, and cytokinin determines meristematic activities in the inflorescence. Strigolactones have been shown to repress the shoot branching but seem to regulate panicle branching positively. Ethylene, brassinosteroids, and gibberellins regulate spikelet abortion and grain filling. Further studies on the optimization of endogenous hormonal levels can help in the expansion of the grain yield potential of rice. This review focuses on the molecular machinery, involving several genes and quantitative trait loci (QTL), operational in the plant that governs hormonal control and, in turn, gets governed by the hormones to regulate grain number and yield in rice.

Effects of Organic and Inorganic Fertilizer Application on Growth, Yield, and Grain Quality of Rice

Nutrient management and fertilizer application are influential elements for high yield and preferred grain quality. Negligible information is available regarding fertilizer application in the paddy fields in Afghanistan. This research elucidates the efficacy of different fertilizers’ application on growth attributes, yield potential, and grain quality of rice. The treatments included the traditional application rate of nitrogen and phosphorus (RD), animal manure (AM), animal manure with 50% nitrogen and phosphorus of the traditional application rate (AMRD), sawdust (SD), and sawdust with 50% nitrogen and phosphorus of the traditional application rate (SDRD). Growth parameters, grain yield and its components, physicochemical properties, and morphological observation using scanning electron microscopy were recorded. The results revealed that the greatest panicle number, spikelet number, and grain yield were recorded in AMRD and SDRD treatments. Both AMRD and SDRD treatments increased the percentage of protein, amylose, and lipid contents, as well as the percentage of perfect grain compared to the RD treatment. Rice grain in RD treatment had very few protein bodies and their traces (pits), as well as the formation of amyloplasts and starch granules, were normal. However, AMRD and SDRD increased the number of protein bodies and their pits in the rice endosperm. The shapes of the amyloplasts were round and polyhedral with diverse sizes. Starch granules were polygonal with sharply defined edges. This research encourages farmers to adopt the combined application of manures and fertilizers to decrease the dependence on inorganic fertilizers.

30 years of free-air carbon dioxide enrichment (FACE): What have we learned about future crop productivity and its potential for adaptation?

Free-air CO2 enrichment (FACE) allows open-air elevation of [CO2 ] without altering the microclimate. Its scale uniquely supports simultaneous study from physiology and yield to soil processes and disease. In 2005 we summarized results of then 28 published observations by meta-analysis. Subsequent studies have combined FACE with temperature, drought, ozone, and nitrogen treatments. Here, we summarize the results of now almost 250 observations, spanning 14 sites and five continents. Across 186 independent studies of 18 C3 crops, elevation of [CO2 ] by ca. 200ppm caused a ca. 18% increase in yield under non-stress conditions. Legumes and root crops showed a greater increase and cereals less. Nitrogen deficiency reduced the average increase to 10%, as did warming by ca. 2°C. Two conclusions of the 2005 analysis were that C4 crops would not be more productive in elevated [CO2 ], except under drought, and that yield responses of C3 crops were diminished by nitrogen deficiency and wet conditions. Both stand the test of time. Further studies of maize and sorghum showed no yield increase, except in drought, while soybean productivity was negatively affected by early growing season wet conditions. Subsequent study showed reduced levels of nutrients, notably Zn and Fe in most crops, and lower nitrogen and protein in the seeds of non-leguminous crops. Testing across crop germplasm revealed sufficient variation to maintain nutrient content under rising [CO2 ]. A strong correlation of yield response under elevated [CO2 ] to genetic yield potential in both rice and soybean was observed. Rice cultivars with the highest yield potential showed a 35% yield increase in elevated [CO2 ] compared to an average of 14%. Future FACE experiments have the potential to develop cultivars and management strategies for co-promoting sustainability and productivity under future elevated [CO2 ].

Genetic determinants for agronomic and yield-related traits localized on a GBS-SNP linkage map from a japonica x indica cross in rice

Rice is an important cereal for human consumption. Identification of QTLs for important agronomic traits with high resolution is essential to the identification of genes and marker-assisted breeding to improve rice productivity. A genotyping by sequencing (GBS)-based high-resolution SNP linkage developed in a recombinant inbred lines (RIL) population of a japonica (Bengal) × indica (Pokkali) cross was used for QTL analysis of traits such as days to heading, plant height, panicle length, flag leaf length, 1000 kernel weight, number of unfilled grains, number of filled grains, grain width, grain length, and awns using interval mapping and inclusive composite interval mapping approaches. Among the 102 additive QTLs identified for the ten traits, 23 QTLs were major effect QTLs. A chromosomal region flanking the sd-1 gene colocalized the QTLs for plant height, panicle length, and flag leaf length, suggesting possible pleiotropic effects on the expression of these traits. Our study not only reduced confidence intervals of previously identified QTLs but also validated several known genes for heading date (Hd1), panicle length (APO1), grain width (GW2, GW5) and awn length (An-1). Furthermore, candidate genes for several agronomic traits were identified. Annotations of genes within novel QTLs for yield-related traits revealed that RCN4 (LOC_Os06g45460), expansin precursor (LOC_Os02g51040), and RGB1 (LOC_Os03g46650) are promising candidates for yield enhancement. Our study provided genetic insights into the important agronomic and yield enhancing traits through identification of QTLs and candidate genes for future validation and molecular breeding to improve rice yield potential.

Phenotyping and QTL mapping for cold tolerance at the germination and seedling stages in Argentine temperate rice

In Argentina, the yield potential of rice (Oryza sativa L.) under suboptimal temperatures of temperate regions and during early sowing in tropical regions depends on its low-temperature germinability (LTG) and subsequent cold tolerance at the seedling stage (CTS). This study focused on the phenotyping and identification of contrasting henotypes for LTG and CTS of 18 rice genotypes genotyped with 49 markers previously linked to cold tolerance. The selected markers revealed phenotypic variability among the genotypes evaluated. The results also demonstrated that both traits are regulated by different genes and that CTS is associated with differential alleles of candidate gene (CG)-based markers. Biplot clustering analysis allowed the selection of two cultivars, H298a/90 and Puita INTA CL, contrasting for LTG, CTS and CG alleles. An F2 population (n = 128) derived from these two cultivars was genotyped with 43 SSR- and CG-based markers and 89 F2:3 families (~ 1800 seedlings) phenotyped for CTS. Single-marker analysis detected two major QTL that had been previously reported for CTS: qCTS11, which explained 18.35% of the phenotypic variance at 7 days of treatment, and qCTS12, which explained 26.62% and 47.94% of the phenotypic variance at 7 and 14 days of treatment, respectively. Marker-assisted introgression of QTL alleles favorable for CTS into Puita INTA CL, which has high LTG, could contribute to obtaining breeding lines with early seedling vigor adapted to the sowing season in Argentina.

Pleiotropic Effect of GNP1 Underlying Grain Number per Panicle on Sink, Source and Flow in Rice.

Rice yield potential is largely determined by the balance among source capacity, sink strength, and flow fluency. Our previous study indicated that the gene GNP1 encoding gibberellin biosynthesis gene GA20ox1 affects grain number per panicle (GNP) in rice, thus resulting in increase of grain yield. To clarify GNP1 effect on sink, source and flow in regulating rice grain yield, we compared Lemont, a japonica (geng) cultivar, with its near-isogenic line (NIL-GNP1TQ) in Lemont background with introgression of the allele at GNP1 from Teqing, a high-yielding indica (xian) cultivar. NIL-GNP1TQ exhibited averagely 32.8% more GNP than Lemont with the compensation by reduced seed setting rate, panicle number and single-grain weight. However, NIL-GNP1TQ still produced averagely 7.2% higher grain yield than Lemont in two years, mainly attributed to significantly more filled grain number per panicle, and greater vascular system contributing to photoassimilates transport to spikelets. The significantly decreased grain weight of superior spikelets (SS) in NIL-GNP1TQ was ascribed to a significant decrease of grain size while the significantly decreased grain weight of inferior spikelets (IS) ascribed to both grain size and poor grain-filling as compared with Lemont. The low activities of key enzymes of carbon metabolism might account for the poor grain-filling in IS, which resulted in more unfilled grains or small grain bulk density in NIL-GNP1TQ. In addition, low seed setting rate and grain weight of IS in NIL-GNP1TQ might be partially resulted from significantly lower carbohydrate accumulation in culms and leaf sheath before heading compared with Lemont. Our results indicated that significantly increased GNP from introgression of GNP1TQ into Lemont did not highly significantly improve grain yield of NIL-GNP1TQ as expected, due primarily to significant low sink activities in IS and possible insufficient source supply which didn’t fully meet the increased sink capacity. The results provided useful information for improving rice yield potential through reasonably introgressing or pyramiding the favorable alleles underlying source-related or panicle number traits by marker-assisted selection.

Genetic Bases of the Stomata-Related Traits Revealed by a Genome-Wide Association Analysis in Rice (Oryza sativa L.).

Stomatal density (D) and size (S) are an important adaptive mechanism for abiotic stress tolerance and photosynthesis capacity in rice. However, the genetic base of rice stomata-related traits still remains unclear. We identified quantitative trait loci (QTLs) associated with D and S on abaxial and adaxial leaf surfaces using genome-wide association analysis with 451 diverse accessions in two environments. D and S showed significant differences between indica (xian) and japonica (geng) accessions and significantly negative phenotypic correlations. A total of 64 QTLs influencing eight stomata-related traits were identified using 2,936,762 high-quality single nucleotide polymorphism markers. Twelve QTLs were consistently detected for the same traits in nine chromosomal regions in both environments. In addition, 12 QTL clusters were simultaneously detected for the same stomata-related traits on abaxial and adaxial leaf surfaces in the same environment, probably explaining the genetic bases of significant correlations of the stomata-related traits. We screened 64 candidate genes for the nine consistent QTL regions using haplotype analysis. Among them, LOC_Os01g66120 for qDada1, OsSPCH2 (LOC_Os02g15760) for qDada2.1 and qDaba2.1, LOC_Os02g34320 for qSada2.2, OsFLP (LOC_Os07g43420) or LOC_Os07g43530 for qSaba7.1, and LOC_Os07g41200 for qWada7 and qWaba7 were considered as the most likely candidate genes based on functional annotations. The results systematically dissected the genetic base of stomata-related traits and provide useful information for improving rice yield potential via increasing abiotic stress tolerance and photosynthesis capacity under stressed and non-stressed conditions through deploying the favorable alleles underlying stomata-related traits by marker-assisted selection.

Characterization of the Common Japonica-Originated Genomic Regions in the High-Yielding Varieties Developed from Inter-Subspecific Crosses in Temperate Rice (Oryza sativa L.).

The inter-subspecific crossing between indica and japonica subspecies in rice have been utilized to improve the yield potential of temperate rice. In this study, a comparative study of the genomic regions in the eight high-yielding varieties (HYVs) was conducted with those of the four non-HYVs. The Next-Generation Sequencing (NGS) mapping on the Nipponbare reference genome identified a total of 14 common genomic regions of japonica-originated alleles. Interestingly, the HYVs shared japonica-originated genomic regions on nine chromosomes, although they were developed through different breeding programs. A panel of 94 varieties was classified into four varietal groups with 38 single nucleotide polymorphism (SNP) markers from 38 genes residing in the japonica-originated genomic regions and 16 additional trait-specific SNPs. As expected, the japonica-originated genomic regions were only present in the japonica (JAP) and HYV groups, except for Chr4-1 and Chr4-2. The Wx gene, located within Chr6-1, was present in the HYV and JAP variety groups, while the yield-related genes were conserved as indica alleles in HYVs. The japonica-originated genomic regions and alleles shared by HYVs can be employed in molecular breeding programs to further develop the HYVs in temperate rice.

High radiation use efficiency improves yield in the recently developed elite hybrid rice Y-liangyou 900

Yield potential in super hybrid rice has continued to increase in recent decades through morphological improvements and the use of inter-subspecific heterosis. Radiation use efficiency (RUE) has been singled out as an important determinant of grain yield in cereal species. However, it is not known whether yield increases in super hybrid rice breeding programs have involved improvements in RUE. Three-year field experiments evaluated the effects of breeding on grain yield and its physiological determinants, including RUE, intercepted photosynthetically active radiation (IPAR), aboveground biomass production, and harvest index (HI), in three representative super hybrid rice varieties released between 1999 and 2015 and grown under three N regimes (N0: 0 kg ha–1, N1: 210 kg ha−1, N2: 300 kg ha–1). Grain yield in the recently developed super hybrid rice cultivar Y-liangyou 900 (YLY900) increased significantly, relative to Liangyoupeijiu (LYPJ) and Y-liangyou 2 (YLY2), reaching more than 11 t ha–1 in the N2 treatment each year. Yield improvements in YLY900 were primarily due to increased aboveground biomass production resulting from a higher RUE, being 10.6 % (biomass) and 12.1 % (RUE) higher than those in LYPJ and YLY2. Unlike YLY900, aboveground biomass accumulation in LYPJ and YLY2 mostly resulted from increased IPAR. Nitrogen supply significantly increased intercepted radiation and intercepted percentage but not RUE. The N treatments had no effect on HI, within or between varieties. Grain yield had a significant (P < 0.01) positive correlation with both intercepted radiation and RUE in all three cultivars. The multiple regression analysis showed that the higher grain yield in YLY900 was more closely related to RUE, while those in LYPJ and YLY2 were highly dependent on intercepted radiation. Considering that YLY900 had a significant yield advantage, we conclude that RUE plays a more prominent role than HI in yield progress in super hybrid rice. Crop breeders should focus on breeding for improved solar radiation properties as a sustainable means of increasing yields in super hybrid rice.

Developing a Proximal Active Canopy Sensor-based Precision Nitrogen Management Strategy for High-Yielding Rice

RapidSCAN is a portable active canopy sensor with red, red-edge, and near infrared spectral bands. The objective of this study is to develop and evaluate a RapidSCAN sensor-based precision nitrogen (N) management (PNM) strategy for high-yielding rice in Northeast China. Six rice N rate experiments were conducted from 2014 to 2016 at Jiansanjiang Experiment Station of China Agricultural University in Northeast China. The results indicated that the sensor performed well for estimating rice yield potential (YP0) and yield response to additional N application (RIHarvest) at the stem elongation stage using normalized difference vegetation index (NDVI) (R2 = 0.60–0.77 and relative error (REr) = 6.2–8.0%) and at the heading stage using normalized difference red edge (NDRE) (R2 = 0.70–0.82 and REr = 7.3–8.7%). A new RapidSCAN sensor-based PNM strategy was developed that would make N recommendations at both stem elongation and heading growth stages, in contrast to previously developed strategy making N recommendation only at the stem elongation stage. This new PNM strategy could save 24% N fertilizers, and increase N use efficiencies by 29–35% as compared to Farmer N Management, without significantly affecting the rice grain yield and economic returns. Compared with regional optimum N management, the new PNM strategy increased 4% grain yield, 3–10% N use efficiencies and 148 $ ha−1 economic returns across years and varieties. It is concluded that the new RapidSCAN sensor-based PNM strategy with two in-season N recommendations using NDVI and NDRE is suitable for guiding in-season N management in high-yield rice management systems. Future studies are needed to evaluate this RapidSCAN sensor-based PNM strategy under diverse on-farm conditions, as well as to integrate it into high-yield rice management systems for food security and sustainable development.

Association analysis of F2 generation in rice (Oryza sativa L.) under salinity condition

Rice occupies a pivotal place in the Indian agriculture and has been grown under diverse ecological conditions and gets exposed to different environmental stresses like drought, salinity and submergence. Development of rice varieties for salinity affected areas is emphasized on the improvement of rice yield potential in a specific environment. Information related to the relationship between yield and its components in the breeding programme particularly for salinity is very limited. Hence, the present investigation was carried out to study the correlation and path analysis in F2 generation derived from two crosses namely ADT 43 x FL478 (Cross 1) and Improved White Ponni x FL478 (Cross 2) were evaluated at a farmer’s field at Vedapatti village, Tuticorin district of Tamil Nadu which is a saline track. Another rice variety FL478 (IR 66946-3R-178-1-1, derived from crossing between Pokkali and IR 29), has been promoted as an improved donor for breeding programs, as it has a high level of seedling stage salinity tolerance and is photoperiod insensitive, shorter and ûowers earlier than the original Pokkali. FL478 also maintains a lower Na+/K+ ratio than both the parent lines (Gregorio et al. 2002). Based on its ability to tiller well and maintain high potassium content under salinity stress, FL478 appears to be a good candidate for salinity stress tolerance in rice, particularly at the vegetative stage of growth. In Vedapatti village of Tuticorin district, due to over-pumping of groundwater in the past several years, normal irrigation water has become saline water. Moreover, this village is considered as a hot spot area for the saline condition. Hence, the six generations developed through hybridization techniques were evaluated for salinity tolerance at Vedapatti village. The soil and water samples were collected from the field to analyze the EC and pH. The soil salinity and water quality in the experimental plot were 4.82 ECdSm-1 and 8.09 (pH) for soil and 4.78 ECdSm-1 and 8.19 (pH) for water respectively. From the present findings, it is clear that the characters viz., number of tillers per plant, number of productive tillers per plant, number of filled grains per panicle, total number of grains per panicle and spikelet fertility have to be given prime importance during selection since they expressed significant and positive correlation with single plant yield and also a positive inter-correlation among themselves. Therefore, selection for anyone of the above characters would bring in the simultaneous improvement of other traits and also finally resort to improve the grain yield under salinity condition. Path analysis also revealed that selection for the number of productive tillers per plant and the number of filled grains per panicle are to be given prior importance during selection since they had a positive correlation and high direct and indirect effect on grain yield under salinity condition in rice.&nbsp

Soil microbial mechanisms promoting ultrahigh rice yield

Improving rice yield potential is crucial for global food security. Taoyuan, China, is famous worldwide as a special ecosite for ultrahigh rice yield. Climatological factors affecting this phenomenon have been identified, but the potential molecular processes and environmental mechanisms promoting ultrahigh yield remain mysteries. This study identifies soil biotic factors affecting ultrahigh yield, considering soil microbial community structure and metagenomic functions during four key rice growth stages, together with results from nitrogen enrichment experiments and rice root transcriptome analysis. Our results show that Taoyuan has more diverse bacterial taxa, less diverse fungal taxa, and a 10-fold-stronger connection among microbial taxa as well as a significantly higher proportion of nutrient transport functions than a regular site. Notably, our metagenomic analysis shows that Taoyuan contains more taxa with nitrogen metabolism functions and a higher abundance of genes involved in the nitrification process (e.g., hydroxylamine oxidoreductase and nitric oxide dioxygenase), promoting effective transformation of ammonium (NH4+) to nitrate (NO3−) in rice fields and stimulating high expression of nitrate transporters in rice roots, leading to ultrahigh yields. Our results indicate that soil microbiota contribute to ultrahigh rice yield in Taoyuan, and indicate that nitrogen metabolism functions could be one of the mechanism for the ultrahigh yield of rice.

Rice Yield and Physiological Characteristics Under Different Panicle Nitrogen Application Timings in Northeast China

Optional nitrogen (N) application management plays an important role in high yield of rice. The results of this study indicated that the grain yield and related physiological indexes were significantly affected by panicle N application timings for conventional japonica rice and hybrid japonica rice. Increasing the number of panicles is an effective method for improving rice yield in Northeast, China. In addition, delaying the timing of spikelet-protecting fertilizer application appropriately might be of great benefit for improving the yield potential of rice.

Effect of multi-allele combination on rice grain size based on prediction of regression equation model.

Rice yield potential is partially affected by grain size and weight, which associates with a great number of genes and QTLs. However, it is still unclear that how multiple alleles in different genes take a combined effect on grain shape/size. Here, we investigated seven core grain size-related functional genes (GL7, GS3, GW8, GS5, TGW6, WTG1, and An-1) and observed a wide phenotypic variation for five agronomic traits (grain length, grain width, grain length-width ratio, grain thickness and thousand-grain weight) in 521 rice germplasm. The correlation analysis showed a strong association among these grain traits which have distinct impacts on determining the final rice grain size. Genotyping analysis demonstrated that a relatively small number of allele combinations were preserved in the diverse population and these allele combinations were significantly associated with differences in grain size. Furthermore, alleles were regarded as individual variables to develop the multiple regression equation. We found that B and C allelic types of GS3 and conventional type of WTG1 played relevant roles in grain size and thousand-grain weight, separately. The models would conduceto devise instructive approaches by selecting appropriate candidate alleles, which could fuel further research for breeding preferred grain shape and high-yielding crop.

Measuring the Efficiency of Rice Production in Myanmar Using Data Envelopment Analysis

Rice production in Myanmar is constrained by biophysical and socioeconomic factors. Nonetheless, efficient farm practices can enhance productivity, farmers’ profit, and the price and quality of marketed rice. This study analyzed the profitability and efficiency of rice production in the Ayeyarwaddy Region of Myanmar and identified the influencing socioeconomic characteristics and farm-specific characteristics. Primary data from 130 randomly sampled farmers in the Ayeyarwaddy Region were collected. Data were analyzed using descriptive statistics, data envelopment analysis (DEA), and Tobit regression analysis. According to the average overall technical efficiency, farmers have an additional rice yield potential of 25 percent that can be attained by improving input utilization. The best practices benchmarked in the region showed that technical inefficiency is caused by excessive use of inputs, especially herbicides and animal power. Most rice farms in this study suffer from allocative and economic inefficiencies resulting from wrong combinations of input usages. The average economic efficiency level indicates that farmers can increase their profitability by 57 percent if they adapted to reduce input costs. Moreover, efficiency was significantly higher for farmers who were younger, better educated, more experienced, had access to agricultural extension services, and cultivated the Aye Yar Min variety. Efficiency can be improved by setting up farmers’ cooperatives to increase the scale of operations. Moreover, the government should intervene to reduce input prices, control the quality of input seeds, and install an appropriate financial crop insurance mechanism. Effective and systematic agricultural extension services should be widespread to improve the efficiency and decision-making skills of rice farmers in the study area.