Super Rice Research Articles

Developing super rice varieties resistant to rice blast with enhanced yield and improved quality.

Developing super rice varieties resistant to rice blast with enhanced yield and improved quality.

Differences in Grain Yield and Nitrogen Uptake between Tetraploid and Diploid Rice: The Physiological Mechanisms under Field Conditions.

Research indicates that, owing to the enhanced grain-filling rate of tetraploid rice, its yield has notably improved compared to previous levels. Studies conducted on diploid rice have revealed that optimal planting density and fertilization rates play crucial roles in regulating rice yield. In this study, we investigated the effects of different nitrogen application and planting density treatments on the growth, development, yield, and nitrogen utilization in tetraploid (represented by T7, an indica-japonica conventional allotetraploid rice) and diploid rice (Fengliangyou-4, represented by FLY4, a two-line super hybrid rice used as a reference variety for the approval of super rice with a good grain yield performance). The results indicated that the highest grain-filling rate of T7 could reach 77.8% under field experimental conditions due to advancements in tetraploid rice breeding. This is a significant improvement compared with the rate seen in previous research. Under the same conditions, T7 exhibited a significantly lower grain yield than FLY4, which could be attributed to its lower grain-filling rate, spikelets per panicle, panicle number m-2, and harvest index score. Nitrogen application and planting density displayed little effect on the grain yield of both genotypes. A higher planting density significantly enhanced the leaf area index and biomass accumulation, but decreased the harvest index score. Compared with T7, FLY4 exhibited a significantly higher nitrogen use efficiency (NUEg), which was mainly due to the higher nitrogen content in the straw. Increasing nitrogen application significantly decreased NUEg due to its minimal effect on grain yield combined with its significant enhancement of nitrogen uptake. Our results suggest that the yield and grain-filling rate of T7 have been improved compared with those of previously tested polyploid rice, but are still lower than those of FLY4, and the yield of tetraploid rice can be further improved by enhancing the grain-filling rate, panicle number m-2, and spikelets per panicle via genotype improvement.

Partial replacement of inorganic fertilizer with organic inputs for enhanced nitrogen use efficiency, grain yield, and decreased nitrogen losses under rice-based systems of mid-latitudes

In the rice-based system of mid-latitudes, mineral nitrogen (N) fertilizer serves as the largest source of the N cycle due to an insufficient supply of N from organic sources causing higher N losses due to varying soil and environmental factors. However, aiming to improve soil organic matter (OM) and nutrients availability using the best environmentally, socially, and economically sustainable cultural and agronomic management practices are necessary. This study aimed to enhance nitrogen use efficiency (NUE) and grain yield in rice-based systems of mid-latitudes by partially replacing inorganic N fertilizer with organic inputs. A randomized complete block design (RCBD) was employed to evaluate the effects of sole mineral N fertilizer (urea) and its combinations with organic sources—farmyard manure (FYM) and poultry compost—on different elite green super rice (GSR) genotypes and were named as NUYT-1, NUYT-2, NUYT-3, NUYT-4, NUYT-5, and NUYT-6. The study was conducted during the 2022 and 2023 rice growing seasons at the Rice Research Program, Crop Sciences Institute (CSI), National Agricultural Research Centre (NARC), Islamabad, one of the mid-latitudes of Pakistan. The key objective was to determine the most effective N management strategy for optimizing plant growth, N content in soil and plants, and overall crop productivity. The results revealed that the combined application of poultry compost and mineral urea significantly enhanced soil and leaf N content (1.36 g kg− 1 and 3.06 mg cm− 2, respectively) and plant morphophysiological traits compared to sole urea application. Maximum shoot dry weight (SDW) and root dry weight (RDW) were observed in compost-applied treatment with the values of 77.62 g hill− 1 and 8.36 g hill− 1, respectively. The two-year mean data indicated that applying 150 kg N ha⁻1, with half provided by organic sources (10 tons ha⁻1 FYM or poultry compost) and the remainder by mineral urea, resulted in the highest N uptake, utilization, and plant productivity. Thus, integrated management of organic carbon sources and inorganic fertilizers may sustain the productivity of rice-based systems more eco-efficiently. Further research is recommended to explore root and shoot morphophysiological, molecular, and biochemical responses under varying N regimes, aiming to develop N-efficient rice varieties through advanced breeding programs.

Resistance of Doubled Haploid Rice Lines with Green Super Rice Characters to Bacterial Leaf Blight

<p>Bacterial leaf blight (BLB), caused by <em>Xanthomonas oryzae</em> pv. <em>oryzae</em> (<em>Xoo</em>) is a significant disease attacking rice crops worldwide. This disease attacks at various stages of plant growth and causes significant yield loss. Breeding new varieties resistant to BLB is important to support sustainable agriculture in the future. This study aimed to identify new superior green super rice (GSR) lines resistant to BLB disease. The experiment evaluated the resistance of lowland rice lines obtained from anther culture using a factorial randomized complete block design. The 1<sup>st</sup> factor was genotype, consisting of 20 lines, 2 checks of commercial varieties (Inpari 42 Agritan GSR and Inpari 18), a resistant check (Conde), and a susceptible check (Taichung Native 1). The 2<sup>nd</sup> factor was BLB pathotypes (i.e., III, IV, and VIII). Quantitative data on disease severity and severity index were analyzed using analysis of variance and t-Dunnett test at 5% level. The results showed that the interaction between genotype and pathotype affected the disease severity and severity index in both growth phases. The tested lines exhibited varying resistance, from susceptible to resistant, to BLB. Four lines (SN 11, 13, 57, and 58) showed moderate to resistant criteria for BLB disease of 3 pathotypes in both growth phases. The selected lines can be used as a source of parents for breeders and candidates for new superior varieties with BLB resistance properties to support the reduction of synthetic chemical bactericide inputs and control BLB disease. However, further field evaluations are necessary to assess their performance.</p>

Yield Difference between Different Cultivation Techniques under Ultrasonic Treatment Driven by Radiation Use Efficiency.

Ultrasonic treatment and optimal cultivation techniques are both conducive to the high yield of super rice in South China. Many previous studies have shown that the increase in intercepted photosynthetically active radiation (IPAR) and radiation use efficiency (RUE) is an important reason for high rice yield. Field experiments were conducted over two years to evaluate the effects of IPAR and RUE on the yield under different treatments (CK: conventional cultivation technique without ultrasonic treatment; T1: conventional cultivation technique with ultrasonic treatment; T2: super rice-specific cultivation technique without ultrasonic treatment and T3: super rice-specific cultivation technique with ultrasonic treatment), with two representative rice varieties, Wufengyou-615 (WFY) and Jingnongsimiao (JNSM) during the late seasons of rice cultivation in South China. The super rice-specific cultivation technique and the ultrasonic treatment could significantly increase the yield, which was significantly (p < 0.01) and positively correlated with panicle number, grain-filling rate, and aboveground total dry weight. The higher grain yield depended more highly on higher RUE in the mid-tillering stage and maturity stage. The results of multiple-regression models also showed that the contributions of IPAR and RUE to yield were significant (p < 0.01). Conclusively, IPAR and RUE contributed a lot to yield progress of super rice in both super rice-specific cultivation techniques with fewer times of topdressing and ultrasonic treatment in South China. It is worth further studying how to reasonably improve the RUE of high-RUE varieties through other means.

Rice breeding for higher crop productivity (a review)

The main global trends in the breeding of rice cultivars and hybrids are higher plant productivity, adaptability to cultivation conditions, quality of products, and resistance to environmental stressors, including diseases.Efforts of leading breeding centers in the Philippines and China to further increase the rice yield are associated with a change in the plant morphotype: shorter plants with erectoid leaves and large panicles with a high number of grains.The International Rice Research Institute (IRRI) has developed rice cultivars that under favorable conditions in the tropical zone produce a grain yield of up to 10–11 t/ha, with Kecon = 0.5. A heterotic hybrid of rice was obtained in China with a yield of 13.9 t/ha; it has a new plant morphotype (New Plant Type) and a growing season of 163 days. The hybrid is classified as “super rice”.Modern breeding programs are aimed at producing cultivars of “Green Super Rice” using pedigree methods and backcrossing for introgression of target genes through DNA markers, QTL mapping, pyramiding, and recurrent selection.Russian breeders have traditionally produced rice cultivars adapted to local conditions, with a growing season of no more than 125 days. In the 1980s, a program was launched to develop a high-yielding rice cultivar with erectoid leaves for condensed planting. As a result of multiple stepwise hybridization and targeted selection, new source material with target traits of “super rice” was released. Cv. ‘Polyus-5’ with a new plant morphotype was obtained on its basis. This cultivar was included in the State Register and from 2023 approved for commercial production. During the field trials, ‘Polyus-5’ yielded a maximum of 1380 g/m2 over 120 days of the growing season, under the conditions of condensed sowing and increased mineral nutrition.

The Effect of Aminocyclopropane Carboxylic Acid (ACC) and Silver Nitrate (AGNO3) on Green Super Rice Seedlings for Submergence Tolerance

This internship reported titled as “The effect of Aminocyclopropane Carboxylic acid (ACC) and Silver Nitrate (AGNO3) on green super rice seedlings for submergence tolerance” aimed to identify submergence tolerant rice genotypes and the role of two chemicals i.e. Aminocyclopropane Carboxylic acid (ACC) and Silver Nitrate (AGNO3) in enhancing submergence tolerance of rice. The trial comprised a pot experiment that was conducted at the experimental field of National Agriculture Research Council (NARC) to evaluate the effect on various newly developed lines of green super rice for submergence tolerance. The experiment was designed in randomized complete block within three replications. The treatments consisted of eleven rice genotypes and two chemicals. Five plants of each genotype were transplanted in to pots which were then treated with ACC, AGNO3 or control (without any chemical). Both these chemicals were applied after one week of transplantation. The data were collected before submergence, after seven days of submergence and after fourteen days of submergence on various agronomic parameters including plant height, leaf length and number of leaves. The results indicated that plant height of genotype NRPC-7 resulted in the tallest plants among all the tested genotypes. Greater leaf length was observed in NRPC-9 in control treatments while maximum number of leaves under the treatment of ACC was observed in genotype NRPC-8. It was concluded that the above-mentioned genotypes were highly tolerated to submergence and can be used in breeding program for submergence tolerant variety development

Country-wide, multi-location trials of Green Super Rice lines for yield performance and stability analysis using genetic and stability parameters

Rice (Oryza sativa L.) is an important member of the family Poaceae and more than half of world population depend for their dietary nutrition on rice. Rice cultivars with higher yield, resilience to stress and wider adaptability are essential to ensure production stability and food security. The fundamental objective of this study was to identify higher-yielding rice genotypes with stable performance and wider adaptability in a rice growing areas of Pakistan. A triplicate RCBD design experiment with 20 Green Super Rice (GSR) advanced lines was conducted at 12 rice growing ecologies in four Provinces of Pakistan. Grain yield stability performance was assessed by using different univariate and multivariate statistics. Analysis of variance revealed significant differences among genotypes, locations, and G x E interaction for mean squares (p < 0.05) of major yield contributing traits. All the studied traits except for number of tillers per plant revealed higher genotypic variance than environmental variance. Broad sense heritability was estimated in the range of 44.36% to 98.60%. Based on ASV, ASI, bi, Wi2, σ2i and WAAS statistics, the genotypes G1, G4, G5, G8, G11 and G12 revealed lowest values for parametric statistics and considered more stable genotypes based on paddy yield. The additive main effects and multiplicative interaction (AMMI) model revealed significant variation (p < 0.05) for genotypes, non-signification for environment and highly significant for G × E interaction. The variation proportion of PC1 and PC2 from interaction revealed 67.2% variability for paddy yield. Based on ‘mean verses stability analysis of GGE biplot’, ‘Which-won-where’ GGE Biplot, ‘discriminativeness vs. representativeness’ pattern of stability, ‘IPCA and WAASB/GY’ ratio-based stability Heat-map, and ranking of genotypes, the genotypes G1, G2, G3, G5, G8, G10, G11 and G13 were observed ideal genotypes with yield potential more than 8 tons ha−1. Discriminativeness vs. representativeness’ pattern of stability identifies two environments, E5 (D.I Khan, KPK) and E6 (Usta Muhammad, Baluchistan) were best suited for evaluating genotypic yield performance. Based on these findings we have concluded that the genotypes G1, G2, G3, G5, G8, G10, G11 and G13 could be included in the commercial varietal development process and future breeding program.

A historical review of hybrid rice breeding.

The development of germplasm resources and advances in breeding methods have led to steady increases in yield and quality of rice (Oryza sativa L.). Three milestones in the recent history of rice breeding have contributed to these increases: dwarf rice breeding, hybrid rice breeding, and super rice breeding. On the 50th anniversary of the success of three-line hybrid rice, we highlight important scientific discoveries in rice breeding that were made by Chinese scientists and summarize the broader history of the field. We discuss the strategies that could be used in the future to optimize rice breeding further in the hope that China will continue to play a leading role in international rice breeding.

Marker-assisted breeding accelerates the development of multiple-stress-tolerant rice genotypes adapted to wider environments.

Rice, one of the major staple food crops is frequently affected by various biotic/abiotic stresses including drought, salinity, submergence, heat, Bacterial leaf blight, Brown plant hopper, Gall midge, Stem borer, Leaf folder etc. Sustained increase of yield growth is highly necessary to meet the projected demand in rice production during the year 2050. Hence, development of high yielding and multiple stress tolerant rice varieties adapted to wider environments will serve the need. A systematic MAB approach was followed to pyramid eight major QTLs/genes controlling tolerance to major abiotic/biotic stresses viz., drought (qDTY1.1 and qDTY2.1), salinity (Saltol), submergence (Sub1), bacterial leaf blight (xa13 and Xa21), blast (Pi9) and gall midge (Gm4) in the genetic background of an elite rice culture CBMAS 14065 possessing high yield and desirable grain quality traits. Two advanced backcross derivatives of CBMAS 14065 possessing different combinations of target QTLs namely #27-1-39 (qDTY1.1+qDTY2.1+Sub1+xa13+Xa21+Gm4+Pi9) and #29-2-2 (qDTY1.1+qDTY2.1+Saltol+Xa21+Gm4+Pi9) were inter-mated. Inter-mated F1 progenies harboring all the eight target QTLs/genes were identified through foreground selection. Genotyping of the inter-mated F4 population identified 14 progenies possessing all eight target QTLs/genes under homozygous conditions. All the fourteen progenies were forwarded up to F8 generation and evaluated for their yield and tolerance to dehydration, salinity, submergence, blast and bacterial leaf blight. All the 14 progenies exhibited enhanced tolerance to dehydration and salinity stresses by registering lesser reduction in their chlorophyll content, relative water content, root length, root biomass etc., against their recurrent parent Improved White Ponni/CBMAS 14065. All the 14 progenies harboring Sub1 loci from FR13A exhibited enhanced survival (90 - 95%) under 2 weeks of submergence /flooding when compared to their recurrent parent CBMAS 14065 which showed 100% susceptibility The inter-mated population showed a enhanced level of resistance to bacterial leaf blight (Score = 0 to 2) against blast (Score - 0) whereas the susceptible check CO 39 and the recurrent parent CBMAS 14065 recorded high level of susceptibility (Score = 7 to 9). Our study demonstrated the accelerated development of multiple stress tolerant rice genotypes through marker assisted pyramiding of target QTLs/genes using tightly linked markers. These multiple stress tolerant rice lines will serve as excellent genetic stocks for field testing/variety release and also as parental lines in future breeding programs for developing climate resilient super rice varieties.

Variability and Correlation Study on Lowland Green Super Rice in Western Ethiopia

Abstract The success of plant breeding activities entirely depends on the existence of genetic variability with respect to desired traits and selection skills of plant breeders. A field experiment was conducted to evaluate the extent of variability, heritability genetic advance, and character association among yield and yield-related traits in lowland GSR. The experiment was conducted using 20 low-land green supper rice genotypes in the Northwestern part of Ethiopia at Pawe agricultural research center for three consecutive years from 2016-2018 main cropping seasons. A randomized complete block design with three replications was used. The results of the analysis of variance for yield and yield-related characters revealed that highly significant mean square due to genotypes observed for all traits studied, Higher phenotypic co-efficient of variation, compared to genotypic co-efficient of variation was recorded for all the traits studied indicating the variation is not only genetic but also influence of growing environment. The highest PCV was recorded for the trait plant height (32.6) followed by panicle length (23.3). Broad sense heritability analysis showed that days to heading (56.3), plant height (49.8), Days to maturity (42.4%), and panicle length (42.3%) were high. High heritability with the high genetic advance in percent of mean was recorded by plant height (49.8 & 33.54) followed by Panicle length (42.3 & 36.55) which confirms their additive gene action and direct selection of these traits depending on phenotypic expression would be effective for yield improvement. The positive and highly significant phenotypic correlation was observed between days to heading and days to maturity (r = 9385***) plant height was positively correlated with thousand-grain weight (0.50436*) and Panicle length (0.48312*). Grain yield showed negative correlation between Days to maturity (-0.044662*), but weak positive correlation was observed for days to heading (r = 0.33472), plant height (r = 0.18729) and panicle length (r = 0.08771). Therefore, the traits recorded high heritability and higher genetic advance; and the traits showed positive correlation and could be considered as suitable traits for selection and improvement to achieve high-yielding green super rice varieties in rain-fed environments.

The comparative transcriptome analysis of two green super rice genotypes with varying tolerance to salt stress.

Salinity is one of the main abiotic factors that restrict plant growth, physiology, and crop productivity is salt stress. About 33% of the total irrigated land suffers from severe salinity because of intensive underground water extraction and irrigation with brackish water. Thus, it is important to understand the genetic mechanism and identify the novel genes involved in salt tolerance for the development of climate-resilient rice cultivars. In this study, two rice genotypes with varying tolerance to salt stress were used to investigate the differential expressed genes and molecular pathways to adapt under saline soil by comparative RNA sequencing at 42 days of the seedling stage. Salt-susceptible (S3) and -tolerant (S13) genotypes revealed 3982 and 3463 differentially expressed genes in S3 and S13 genotypes. The up-regulated genes in both genotypes were substantially enriched in different metabolic processes and binding activities. Biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, and plant signal transduction mechanisms were highly enriched. Salt-susceptible and -tolerant genotypes shared the same salt adaptability mechanism with no significant quantitative differences at the transcriptome level. Moreover, bHLH, ERF, NAC, WRKY, and MYB transcription factors were substantially up-regulated under salt stress. 391 out of 1806 identified novel genes involved in signal transduction mechanisms. Expression profiling of six novel genes further validated the findings from RNA-seq data. These findings suggest that the differentially expressed genes and molecular mechanisms involved in salt stress adaptation are conserved in both salt-susceptible and salt-tolerant rice genotypes. Further molecular characterization of novel genes will help to understand the genetic mechanism underlying salt tolerance in rice.

Culturomics and Amplicon-Based Metagenomic Insights into the Bacteria of Soils with High Yield of Oryza sativa L. subsp. Japonica

The bacterial community in the paddy field agroecosystem has a pivotal role in the growth adaptability strategy of rice. Here, we studied the bacterial community structure composition of rhizosphere and non-rhizosphere soil samples from super rice in high-yield (920.99 kg/mu) and low-yield (785.30 kg/mu) fields of Japonica Chu 54 using both culturomics and amplicon-based metagenomics approaches. Using amplicon sequencing, a total of 54 phyla and 1167 genera of high-yield field bacteria were detected, while the low-yield field bacteria were distributed in 49 phyla and 865 genera. In addition, compared with low-yielding fields, there were significant differences in the composition and abundance of the same members in high-yielding fields. The node microorganisms in high-yield and low-yield fields were Anaeromyxobacterium and HSB_OF53-F07, respectively. Culturomics analysis unveiled a diverse array of bacterial taxa, encompassing four phyla, 113 genera, and 331 species, including 33 new undescribed lineages. The culturomics and high-throughput sequencing results indicate a widely adapted and highly abundant group of Exiguobacterium, which has broad prospects for application due to its extensive survival characteristics and plant growth-promoting functions. In summary, we analyze the bacterial community structure composition of rhizosphere and non-rhizosphere soil samples from super rice in high-yield and low-yield fields of Japonica Chu 54 using culturomics and amplicon sequencing techniques to better develop positive promotion strategies that adapt to its unique ecological environment.

Synergistic Effects of N Fertilization and Irrigation on Soil Bacterial Community in Super Rice Paddies

Nitrogen reduction, in association with increased planting density and irrigation management, has been widely adopted in super rice cultivation systems to pursue higher yield with lower input. Here, soil microbial community structures under accurate N and water management were investigated after four years of experiments. Plot experiments were conducted with three treatments, including conventional farming practice (CF), reduced nitrogen with increased plant density (RNID), and reduced nitrogen with increased plant density and precise irrigation (RNIDPI). The results showed that RNID treatment increased soil bacterial diversity, enriched biomarker bacterial taxa, and altered bacterial community structure, with pH as the influential factor. The phylum Chloroflexi was enriched in the treatment of N reduction, while a higher ratio of Firmicutes was present in CF treatments. RNID treatment witnessed a low proportion of bacterial functional groups involved in nitrification and nitrate reduction. N fertilizer reduction with irrigation management increased rice yield (up to 22%) without changing the major soil fertility properties except for the increased pH and decreased ammonium N. The results suggest that N reduction, in association with increased plant density and accurate irrigation, is beneficial for super rice production.

Design and Experimental Investigation of a Transplanting Mechanism for Super Rice Pot Seedlings

Super rice contains a variety of advantageous characteristics. However, current rice seedling transplanting machines fail to achieve the necessary trajectory and distance required for super rice mechanized transplanting. To address this issue, this study introduces a differential-speed rotary mechanism for transplanting super rice pot seedlings. The developed mechanism operates using a non-uniform speed differential gear train, which enables the transplanting arm components to mimic the specific trajectory and posture necessary for transplanting super rice pot seedlings. The kinematic model of the differential-speed rotary super rice pot seedling transplanting mechanism (PSTM) was established, and optimization design software was developed. This software facilitated the determination of a set of mechanism parameters optimized for super rice pot seedling transplantation. The results obtained from virtual simulations were found to be in alignment with those from the optimization software, thereby verifying the accuracy of the theoretical analysis and simulation. A testing bench for the rice PSTM was also developed and used for pot seedling pickup experiments. The bench tests demonstrated that the designed super rice PSTM yielded a seedling pickup success rate of 97% and a seedling injury rate of 1.8% when operating at an efficiency of 200 times/min.

Influence of Chemical, Organic, and Biological Silicon Fertilization on Physiological Studies of Egyptian Japonica Green Super Rice (Oryza sativa L.)

Rice plants are known to be silicon (Si) accumulators, hence farmers often use specific commercial chemical fertilizers to meet the nutrient needs of plants. Farmers commonly use fertilizers that are expensive and produce immediate effects, yet they contaminate the soil, water, and air. We should reduce the use of chemical fertilizers by combining a part of them with alternative organic and biological sources of Si, such as rice husk and Bacillus mucilaginosus (Si-solubilizing bacteria). Furthermore, it rationalizes chemical fertilizer consumption, reduces environmental pollution, and improves nutrient use efficiency to achieve rationalization of consumption with economic benefits in spending and rationalization of consumption of chemicals polluting the environment. In two successive growth seasons, 2021 and 2022, a field experiment was conducted to determine the effects of chemical, organic, and biological silicon fertilization in physiological studies of Egyptian Japonica green super rice. A randomized complete block design was used, with four replications, and the following treatments were used: T1, recommended dose of silica gel (SG; chemical Si); T2, recommended dose of rice husk (RH; organic Si); T3, recommended dose of Si-solubilizing bacteria (SSB; Bacillus mucilaginosus; biological Si); T4, ½ SG + ½ RH; T5, ½ SG + ½ SSB; T6, ½ RH + ½ SSB; T7, 1/3 SG + 1/3 RH + 1/3 SSB; T8, zero chemical, organic, and biological Si (control). The results showed that the application of silica gel as a chemical Si fertilizer, rice husk as an organic Si fertilizer, and Bacillus mucilaginosus as a Si-solubilizing bacteria or biological Si fertilizer source resulted in significantly higher yields of grain (10.71 and 10.53) t ha−1 and straw (12.66 and 12.37) t ha−1 in 2021 and 2022, respectively. Following that, silica gel, when combined with Si-solubilizing bacteria, led to increases in grain yield output of 10.32 and 10.39 t ha−1 and straw yield of 12.16 and 12.05 t ha−1 in 2021 and 2022, respectively. In addition, yield attributes, chlorophyll content in leaves, flag leaf area, flag leaf weight, chlorophyll in flag leaf, crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), and silicon uptake in grain and straw were determined as follows: The application of silica gel as a chemical Si fertilizer, rice husk as an organic Si fertilizer, and Bacillus mucilaginosus as a Si-solubilizing bacteria or biological Si fertilizer source had a substantial impact on all examined characteristics. According to the optimal treatment, one part of the three parts of Si fertilization utilized just chemical Si fertilizer and the other two parts organic and biological Si. So we can minimize chemical fertilizer use and reduce soil pollution. The findings of this study will be valuable for future research, such as the usage of alternative organic and biological sources of Si in rice.

An optimized strategy of nitrogen-split application based on the leaf positional differences in chlorophyll meter readings

Modern rice production faces the dual challenges of increasing grain yields while reducing inputs of chemical fertilizer. However, the disequilibrium between the nitrogen (N) supplement from the soil and the demand for N of plants is a serious obstacle to achieving these goals. Plant-based diagnosis can help farmers make better choices regarding the timing and amount of topdressing N fertilizer. Our objective was to evaluate a non-destructive assessment of rice N demands based on the relative SPAD value (RSPAD) due to leaf positional differences. In this study, two field experiments were conducted, including a field experiment of different N rates (Exp. I) and an experiment to evaluate the new strategy of nitrogen-split application based on RSPAD (Exp. II). The results showed that higher N inputs significantly increased grain yield in modern high yielding super rice, but at the expense of lower nitrogen use efficiency (NUE). The N nutrition index (NNI) can adequately differentiate situations of excessive, optimal, and insufficient N nutrition in rice, and the optimal N rate for modern high yielding rice is higher than conventional cultivars. The RSPAD is calculated as the SPAD value of the top fully expanded leaf vs. the value of the third leaf, which takes into account the non-uniform N distribution within a canopy. The RSPAD can be used as an indicator for higher yield and NUE, and guide better management of N fertilizer application. Furthermore, we developed a new strategy of nitrogen-split application based on RSPAD, in which the N rate was reduced by 18.7%, yield was increased by 1.7%, and the agronomic N use efficiency was increased by 27.8%, when compared with standard farmers’ practices. This strategy of N fertilization shows great potential for ensuring high yielding and improving NUE at lower N inputs.

Agronomic performance and selection of green super rice doubled haploid lines from anther culture

Abstract. Nurhidayah S, Purwoko BS, Dewi IS, Suwarno WB, Lubis I. 2023. Agronomic performance and selection of green super rice doubled haploid lines from anther culture. Biodiversitas 24: 819-826. Rice is the staple food of most Asian, including Indonesian people. Plant breeding plays an important role in producing high-yielding varieties of rice to meet national carbohydrate sufficiency. Green Super Rice (GSR) is an alternative for rice variety development that has the advantages of high yield, good quality, pest resistance, and efficient fertilizer use to support sustainable agriculture. This study aimed to evaluate the agronomic character of GSR doubled haploid (DH) lines derived from anther culture and determine the best GSR rice lines based on index selection. The treatment was 65 genotypes consisting of 60 DH of GSR lines from anther culture of 5 combinations of crosses and 5 check varieties. The study used a randomized complete block design with three replications. The results showed that most of the tested lines had similar agronomic performances to the check variety Inpari 42 Agritan GSR. Almost all agronomic characters of the GSR DH lines had high genetic variability. Most characters had a high category of broad-sense heritability except panicle length. Line selection using index selection for economically important agronomic characters yielded 27 GSR DH lines having high productivity, number of productive tillers per hill, number of total grains per panicle, and percentage of filled grains per panicle.

Identification of photosynthetic parameters for superior yield of two super hybrid rice varieties: A cross-scale study from leaf to canopy.

Enhancing photosynthetic capacity is widely accepted as critical to advancing crop yield. Therefore, identifying photosynthetic parameters positively related to biomass accumulation in elite cultivars is the major focus of current rice research. In this work, we assessed leaf photosynthetic performance, canopy photosynthesis, and yield attributes of super hybrid rice cultivars Y-liangyou 3218 (YLY3218) and Y-liangyou 5867 (YLY5867) at tillering stage and flowering stage, using inbred super rice cultivars Zhendao11(ZD11) and Nanjing 9108 (NJ9108) as control. A diurnal canopy photosynthesis model was applied to estimate the influence of key environmental factors, canopy attributes, and canopy nitrogen status on daily aboveground biomass increment (AMDAY). Results showed that primarily the light-saturated photosynthetic rate at tillering stage contributed to the advancing yield and biomass of super hybrid rice in comparison to inbred super rice, and the light-saturated photosynthetic rate between them was similar at flowering stage. At tillering stage, the higher CO2 diffusion capacity, together with higher biochemical capacity (i.e., maximum carboxylation rate of Rubisco, maximum electron transport rate (J max), and triose phosphate utilization rate) favored leaf photosynthesis of super hybrid rice. Similarly, AMDAY in super hybrid rice was higher than inbred super rice at tillering stage, and comparable at flowering stage partially due to increased canopy nitrogen concentration (SLNave) of inbred super rice. At tillering stage, model simulation revealed that replacement of J max and g m in inbred super rice by super hybrid rice always had a positive effect on AMDAY, and the averaged AMDAY increment was 5.7% and 3.4%, respectively. Simultaneously, the 20% enhancement of total canopy nitrogen concentration through the improvement of SLNave (TNC-SLNave) resulted in the highest AMDAY across cultivars, with an average increase of 11.2%. In conclusion, the advancing yield performance of YLY3218 and YLY5867 was due to the higher J max and g m at tillering stage, and TCN-SLNave is a promising target for future super rice breeding programs.

Optimizing Agronomy Improves Super Hybrid Rice Yield and Nitrogen Use Efficiency through Enhanced Post-Heading Carbon and Nitrogen Metabolism

The super hybrid rice breeding program in China has raised genetic yield ceilings through morphological improvements and inter-subspecific heterosis. Despite this, little information on the physiological basis underlying this yield transformation exists, and less so on the genotype x environment x management conditions enabling consistent yield gains. Here, we assess grain yield, photosynthetic physiology, and leaf carbon and nitrogen (N) metabolic properties of super rice (Y-liangyou900) under four management practices (i.e., zero-fertilizer control, CK; farmers’ practice, FP; high-yield and high-efficiency management, OPT1; and super-high-yield management, OPT2) using a field experiment conducted over five years. Grain yield and agronomic N use efficiency (AEN) of OPT2 were 15% and 10% higher than OPT1, and 30% and 78% higher than FP, respectively. The superior yields of OPT2 were attributed to higher source production capacity, that is, higher leaf photosynthetic rate, carbon metabolic enzyme activity (i.e., AGP and SPS), nitrogen metabolic enzyme activity (i.e., NR, GS, and GOGAT), soluble protein and sugar content, and delayed leaf senescence (the latter due to elevated activity of protective enzyme systems) during grain filling. The higher AEN of OPT2 was associated with higher activity of leaf carbon metabolic enzyme (i.e., AGP and SPS), nitrogen metabolic enzyme (i.e., NR, GS, GDH, and GOGAT) and protective enzyme (POD) after heading, and lower C/N ratio in grains. We conclude that optimized management (optimized water and fertilizer management with appropriate dense planting) improved grain yield and N use efficiency simultaneously by enhancing post-heading leaf carbon and N metabolism and delayed leaf senescence.