Yield Traits In Rice Research Articles

Chitosan-based NPK nanostructure for reducing synthetic NPK fertilizers and improving rice productivity and nutritional indices

Researchers have repeatedly emphasized how urgently we have to decrease the massive nitrogen fertilizer consumption to support agricultural productivity and maintain a sustainable ecosystem. Using chitosan (CS) as a carrier for slow release is considered a potential tool for reducing synthetic fertilizer and improving crop productivity. Therefore, two field experiments were arranged in a randomized complete block design to investigate the effects of seven treatments including synthetic fertilizer and exogenous application of chitosan-based NPK nano-structure (Ch/NPs-NPK) on growth, productivity, and nutrient uptake traits of rice as a worldwide strategy crop during 2022 and 2023 growing seasons. The experimental treatments were: T1 = full recommended synthetic NPK (recommended urea, superphosphate, potassium sulfate; control treatment), T2 = 70% of T1 + Ch/NPs-NPK 100 ppm, T3 = 70% of T1+ Ch/NPs-NPK 200 ppm, T4 = 70% of T1+ Ch/NPs-NPK 300 ppm, T5 = 30% of T1+ Ch/NPs-NPK 100 ppm, T6 = 30% of T1+ Ch/NPs-NPK 200 ppm, and T7 = 30% of T1 + Ch/NPs-NPK 300 ppm. The results revealed that T4 (i.e., 70% of recommended NPK+ Ch/NPs-NPK 300 ppm) and T1 (full recommended synthetic NPK) resulted in the highest and most significant growth and yield traits of rice as well as nutrient grain contents compared to other treatments. Therefore, combining 70% of recommended NPK with Ch/NPs-NPK 300 ppm as an exogenous application can be a smart choice for reducing synthetic NPK fertilizers by 30% in paddy fields without producing a significant decline in terms of growth, yield characteristics, or nutrient grain contents when applying the full recommended synthetic NPK.

Limonene enhances rice plant resistance to a piercing-sucking herbivore and rice pathogens.

Terpene synthases (TPSs) are key enzymes in terpenoids synthesis of plants and play crucial roles in regulating plant defence against pests and diseases. Here, we report the functional characterization of OsTPS19 and OsTPS20, which were upregulated by the attack of brown planthopper (BPH). BPH female adults performed concentration-dependent behavioural responses to (S)-limonene showing preference behaviour at low concentrations and avoidance behaviour at high concentrations. Overexpression lines of OsTPS19 and OsTPS20, which emitted higher amounts of the monoterpene (S)-limonene, decreased the hatching rate of BPH eggs, reduced the lesion length of sheath blight caused by Rhizoctonia solani and bacterial blight caused by Xanthomonas oryzae. While knockout lines of OsTPS19 and OsTPS20, which emitted lower amounts of (S)-limonene, were more susceptible to these pathogens. Overexpression of OsTPS19 and OsTPS20 in rice plants had adverse effects on the incidence of BPH, rice blast, and sheath blight in the field and had no significant impacts on rice yield traits. OsTPS19 and OsTPS20 were found to be involved in fine-tuning the emission of (S)-limonene in rice plants and play an important role in defence against both BPH and rice pathogens.

A Study on the Impacts of Fertilizer Crisis on Paddy Cultivation in Five Selected Divisional Secretariat Divisions of Trincomalee District During Maha 2021/22

Rice is one of the most important cereal crops in the world. With population growth, farmers have to increase paddy production to meet existing as well as future demand. Fertilizer is the major input in rice production. Growth and yield traits of rice are affected by improper and imbalanced application of plant nutrients. Hence, suitable practices of adequate rate and timing of fertilizer application are needed to increase the rice yield. In May 2021, Imports & Exports (Control) Regulation No 07 of 2021 was issued, banning the importation of chemical fertilizers, pesticides, & herbicides in Sri Lanka. Low fertility of paddy soil created the need for adequate and constant supply of chemical fertilizers in paddy cultivation, which is a major threat to production and endangers the national food security and economy of Sri Lanka, especially in the major cropping season of Maha 2021/22. Therefore, a questionnaire survey was conducted to investigate the impact of the fertilizer crisis in major paddy-cultivating Divisional Secretariat divisions of the Trincomalee district. The random sampling method was used to select respondents for the survey, and the collected data were statistically analyzed by SPSS version 26.0 software. The results revealed that the majority of the farmers experienced a 50% yield reduction compared to the last cropping season of Maha 2020/21 in the entire five DS divisions. The seedling stage was highly affected during the fertilizer crisis in paddy cultivation in all five DS divisions. Further, the cost of production in paddy cultivation increased by more than 50% during the fertilizer crisis compared to the cost involved in Maha 2020/21. The potential for organic manure production is very poor, while the majority of farmers are interested in adopting the sustainable farming system of the Integrated Plant Nutrient System through the judicious application of chemical and organic fertilizers received on a subsidy basis, according to the present government’s fertilizer policy, which emphasizes 70% of inorganic fertilizers and 30% of organic manure application to improve sustainability in paddy cultivation in the country.

OsEXPA7 Encoding an Expansin Affects Grain Size and Quality Traits in Rice (Oryza sativa L.)

BackgroundYield and quality are the two most important traits in crop breeding. Exploring the regulatory mechanisms that affect both yield and quality traits is of great significance for understanding the molecular genetic networks controlling these key crop attributes. Expansins are cell wall loosening proteins that play important roles in regulating rice grain size.ResultsWe investigated the effect of OsEXPA7, encoding an expansin, on rice grain size and quality. OsEXPA7 overexpression resulted in increased plant height, panicle length, grain length, and thousand-grain weight in rice. OsEXPA7 overexpression also affected gel consistency and amylose content in rice grains, thus affecting rice quality. Subcellular localization and tissue expression analyses showed that OsEXPA7 is localized on the cell wall and is highly expressed in the panicle. Hormone treatment experiments revealed that OsEXPA7 expression mainly responds to methyl jasmonate, brassinolide, and gibberellin. Transcriptome analysis and RT-qPCR experiments showed that overexpression of OsEXPA7 affects the expression of OsJAZs in the jasmonic acid pathway and BZR1 and GE in the brassinosteroid pathway. In addition, OsEXPA7 regulates the expression of key quantitative trait loci related to yield traits, as well as regulates the expression levels of BIP1 and bZIP50 involved in the seed storage protein biosynthesis pathway.ConclusionsThese results reveal that OsEXPA7 positively regulates rice yield traits and negatively regulates grain quality traits by involving plant hormone pathways and other trait-related pathway genes. These findings increase our understanding of the potential mechanism of expansins in regulating rice yield and quality traits and will be useful for breeding high-yielding and high-quality rice cultivars.

New insights into QTNs and potential candidate genes governing rice yield via a multi-model genome-wide association study

BackgroundRice (Oryza sativa L.) is one of the globally important staple food crops, and yield-related traits are prerequisites for improved breeding efficiency in rice. Here, we used six different genome-wide association study (GWAS) models for 198 accessions, with 553,229 single nucleotide markers (SNPs) to identify the quantitative trait nucleotides (QTNs) and candidate genes (CGs) governing rice yield.ResultsAmongst the 73 different QTNs in total, 24 were co-localized with already reported QTLs or loci in previous mapping studies. We obtained fifteen significant QTNs, pathway analysis revealed 10 potential candidates within 100kb of these QTNs that are predicted to govern plant height, days to flowering, and plot yield in rice. Based on their superior allelic information in 20 elite and 6 inferior genotypes, we found a higher percentage of superior alleles in the elite genotypes in comparison to inferior genotypes. Further, we implemented expression analysis and enrichment analysis enabling the identification of 73 candidate genes and 25 homologues of Arabidopsis, 19 of which might regulate rice yield traits. Of these candidate genes, 40 CGs were found to be enriched in 60 GO terms of the studied traits for instance, positive regulator metabolic process (GO:0010929), intracellular part (GO:0031090), and nucleic acid binding (GO:0090079). Haplotype and phenotypic variation analysis confirmed that LOC_OS09G15770, LOC_OS02G36710 and LOC_OS02G17520 are key candidates associated with rice yield.ConclusionsOverall, we foresee that the QTNs, putative candidates elucidated in the study could summarize the polygenic regulatory networks controlling rice yield and be useful for breeding high-yielding varieties.

Genome-wide association studies for a comprehensive understanding of the genetic architecture of culm strength and yield traits in rice.

Lodging resistance in rice is a complex trait determined by culm morphological and culm physical strength traits, and these traits are a major determinant of yield. We made a detailed analysis of various component traits with the aim of deriving optimized parameters for measuring culm strength. Genotyping by sequencing (GBS)-based genome-wide association study (GWAS) was employed among 181 genotypes for dissecting the genetic control of culm strength traits. The VanRaden kinship algorithm using 6,822 filtered single-nucleotide polymorphisms (SNPs) revealed the presence of two sub-groups within the association panel with kinship values concentrated at<0.5 level, indicating greater diversity among the genotypes. A wide range of phenotypic variation and high heritability for culm strength and yield traits were observed over two seasons, as reflected in best linear unbiased prediction (BLUP) estimates. The multi-locus model for GWAS resulted in the identification of 15 highly significant associations (p< 0.0001) for culm strength traits. Two novel major effect marker-trait associations (MTAs) for section modulus and bending stress were identified on chromosomes 2 and 12 with a phenotypic variance of 21.87% and 10.14%, respectively. Other MTAs were also noted in the vicinity of previously reported putative candidate genes for lodging resistance, providing an opportunity for further research on the biochemical basis of culm strength. The quantitative trait locus (QTL) hotspot identified on chromosome 12 with the synergistic association for culm strength trait (section modulus, bending stress, and internode breaking weight) and grain number can be considered a novel genomic region that can serve a dual purpose of enhancing culm strength and grain yield. Elite donors in the indica background with beneficial alleles of the identified major QTLs could be a valuable resource with greater significance in practical plant breeding programs focusing on improving lodging resistance in rice.

Identification of NADPH Oxidase Genes Crucial for Rice Multiple Disease Resistance and Yield Traits

Reactive oxygen species (ROS) act as a group of signaling molecules in rice functioning in regulation of development and stress responses. Respiratory burst oxidase homologues (Rbohs) are key enzymes in generation of ROS. However, the role of the nine Rboh family members was not fully understood in rice multiple disease resistance and yield traits. In this study, we constructed mutants of each Rboh genes and detected their requirement in rice multiple disease resistance and yield traits. Our results revealed that mutations of five Rboh genes (RbohA, RbohB, RbohE, RbohH, and RbohI) lead to compromised rice blast disease resistance in a disease nursery and lab conditions; mutations of five Rbohs (RbohA, RbohB, RbohC, RbohE, and RbohH) result in suppressed rice sheath blight resistance in a disease nursery and lab conditions; mutations of six Rbohs (RbohA, RbohB, RbohC, RbohE, RbohH and RbohI) lead to decreased rice leaf blight resistance in a paddy yard and ROS production induced by PAMPs and pathogen. Moreover, all Rboh genes participate in the regulation of rice yield traits, for all rboh mutants display one or more compromised yield traits, such as panicle number, grain number per panicle, seed setting rate, and grain weight, resulting in reduced yield per plant except rbohb and rbohf. Our results identified the Rboh family members involved in the regulation of rice resistance against multiple pathogens that caused the most serious diseases worldwide and provide theoretical supporting for breeding application of these Rbohs to coordinate rice disease resistance and yield traits.

Identification of candidate genes and favourable haplotypes for yield traits in rice based on a genome-wide association study

Identification of candidate genes and favourable haplotypes for yield traits in rice based on a genome-wide association study

Functional characterization and allelic mining of OsGLR genes for potential uses in rice improvement.

Glutamate-like receptor (GLR) genes are a group of regulatory genes involved in many physiological processes of plants. With 26 members in the rice genome, the functionalities of most rice GLR genes remain unknown. To facilitate their potential uses in rice improvement, an integrated strategy involving CRISPR-Cas9 mediated knockouts, deep mining and analyses of transcriptomic responses to different abiotic stresses/hormone treatments and gene CDS haplotype (gcHap) diversity in 3,010 rice genomes was taken to understand the functionalities of the 26 rice GLR genes, which led us to two conclusions. First, the expansion of rice GLR genes into a large gene family during evolution had gone through repeated gene duplication events occurred primarily in two large GLR gene clusters on rice chromosomes 9 and 6, which was accompanied with considerable functional differentiation. Secondly, except for two extremely conserved ones (OsGLR6.2 and OsGLR6.3), rich gcHap diversity exists at the remaining GLR genes which played important roles in rice population differentiation and rice improvement, evidenced by their very strong sub-specific and population differentiation, by their differentiated responses to day-length and different abiotic stresses, by the large phenotypic effects of five GLR gene knockout mutants on rice yield traits, by the significant association of major gcHaps at most GLR loci with yield traits, and by the strong genetic bottleneck effects and artificial selection on the gcHap diversity in populations Xian (indica) and Geng (japonica) during modern breeding. Our results suggest the potential values of the natural variation at most rice GLR loci for improving the productivity and tolerances to abiotic stresses. Additional efforts are needed to determine the phenotypic effects of major gcHaps at these GLR loci in order to identify 'favorable' alleles at specific GLR loci specific target traits in specific environments to facilitate their application to rice improvement in future.

Genetic Variability for Growth and Yield Traits in Rice

Genetic variability is necessary for any crop breeding program to develop superior varieties. The objective was to estimate the genetic variability for growth and yield traits. The experiment was carried out at Baijanath-4, Banke district, Province no. 5 Nepal during June to November, 2019. Eleven rice genotypes were evaluated in a randomized complete block design with three replications. Days to flowering, days to maturity, panicle length, plant height, number of panicle per hill, number of tiller perhill, grain yield and thousand grain weights were found significant. Moreover, number of panicle perhill having high heritability (79%) have maximum genotypic coefficient of variation (29.03). Further, thousand grain weight, grain yield, plant height need to be considered as effective traits for breeding material selection. PB 1509 was declared superior genotype among aromatic genotype and also found as effective genotype with short height, more thousand grain weight, higher yield potential than compare to check HH1. Thus, the exploitation of PB1509 in further yield trial will contribute to National Rice Breeding Programs of Nepal.

Advances in cloning functional genes for rice yield traits and molecular design breeding in China.

Rice, a major food crop in China, contributes significantly to international food stability. Advances in rice genome sequencing, bioinformatics, and transgenic techniques have catalyzed Chinese researchers' discovery of novel genes that control rice yield. These breakthroughs in research also encompass the analysis of genetic regulatory networks and the establishment of a new framework for molecular design breeding, leading to numerous transformative findings in this field. In this review, some breakthroughs in rice yield traits and a series of achievements in molecular design breeding in China in recent years are presented; the identification and cloning of functional genes related to yield traits and the development of molecular markers of rice functional genes are summarized, with the intention of playing a reference role in the following molecular design breeding work and how to further improve rice yield.

Spinel nanocomposite (nMnZnFe2O4) synchronously promotes grain yield and Fe–Zn biofortification in non-aromatic rice

Soils deficient in essential micro-nutrients produce nutritionally starved crops that do not fulfill human nutritional requirements. This is getting serious since progressively increasing nutritional disorders are being diagnosed in residents of third-world countries like Pakistan. During this study, we synthesized a spinel nanocomposite (nMnZnFe2O4) and investigated its effectiveness in improving the micronutrient status and yield traits of rice. The nMnZnFe2O4 exhibited a cubic structure at the most prominent peak (311); a crystallite size of 44 nm, and an average grain size ranging from 7 to 9 μm. Foliar application of this nanocomposite was performed to 45 days old plants at concentrations 0, 10, 20, 30, 40, and 50 mg L−1, and data from rice plant parts (straw, husk, and grain) was recorded at maturity. Agronomic traits like the number of tillers, straw dry weight, root dry biomass, and grain yield per plant were improved by nMnZnFe2O4 application (+34.4% yield). Whereas some biochemical traits like amino acids, soluble sugars, flavonoids, and phenolics varied significantly in rice plant parts compared to the control. Above all, the maximum Zn and Fe concentrations in rice grain were recorded through foliar application of spinel nanocomposite (40 and 50 mg L−1). Therefore, results indicated that micronutrient supply in the form of a nanocomposite could positively regulate nutritional quality and rice grain yield.

A novel method for intelligent analysis of rice yield traits based on LED transmission imaging and cloud computing

Rice yield traits extraction is necessary for rice breeding and genetic analysis, in which the discrimination of filled and unfilled grain was the bottleneck. The traditional methods including wind separating and water sinking are inefficient, unreliable, and poorly reproducible, meanwhile the machine vision methods based on X-ray and 3D structured imaging have the disadvantages of high cost, ionizing radiation, and poor scalability. To address the above problems, this study has proposed a novel method for intelligent analysis of rice yield traits based on LED transmission imaging and cloud application. The study has found that the red-light LED transmission imaging was able to obtain high-contrast images of filled and unfilled grains and had the advantages of radiation-free, low-cost, and high-efficiency imaging. Using 3,200 rice grain images as the training set, the results showed that the YOLOv5 model outperformed the Faster RCNN, RetinaNet, SSD, and Cascade RCNN models, and its filled and unfilled grain recognition precision was 98.94% and 90.96% on the 800 test sets, while the recall rate was 97.91% and 94.94%. To further improve the recognition accuracy of the YOLOv5 model, five model optimization methods were adopted in the study, including TPH, CBAM, adding a small target detection layer, using Bi-FPN and Multi-NMS. The results proved that the accuracy of unfilled grain recognition had significantly improved, the recognition precision increased by 4.54% to 95.44%, and the recall rate increased by 0.77% to 95.71%. Finally, this study has designed the specified algorithms based on the recognized rectangular box, which could accurately measure filled and unfilled grain numbers, seed setting rate and grain shape parameters. Moreover, the study has designed a local Qt software and a cloud-based website, which can support the simultaneous input of multiple images with high real-time performance and good scalability, providing a practical novel tool for rice breeding and genetic analysis.

Effects of prohexadione calcium spraying during the booting stage on panicle traits, yield, and related physiological characteristics of rice under salt stress.

Prohexadione calcium (Pro-Ca), as a growth retardant, can effectively alleviate the damage of salt stress to plants. In order to explore the effects of NaCl stress on the physiological characteristics and panicle traits of rice plants as well as the alleviating effect of Pro-Ca at the booting stage, we performed pot experiments on two rice cultivars: conventional rice 'Huanghuazhan' and hybrid rice 'Xiangliangyou900'. Rice plants were treated with 0.3% NaCl 48 hours after Pro-Ca (100 mg L-1) treatment to study the effects of Pro-Ca on the physiological characteristics of the leaves and panicles, as well as the panicle and yield traits of rice under salt stress. Our analysis indicated that NaCl treatment inhibited the morphological growth parameters and photosynthetic efficiency, destroyed the antioxidant defense systems of leaves and panicles, increased soluble protein and proline in both rice cultivars. Foliar application of Pro-Ca significantly increased the leaf area, uppermost internode length, panicle length, panicle weight, number of primary branches, number of grains per panicle, seed setting rate and yield under salt stress. Pro-Ca application significantly affected chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and apparent mesophyll conductance (AMC) in NaCl-treated rice cultivars compared with NaCl treatment alone. Moreover, Pro-Ca also increased ascorbic acid (AsA) content, enhanced superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity, and further increased the accumulation of soluble protein and proline in leaves and panicles. These results illustrated that foliar application of Pro-Ca at the booting stage could alleviate the damage caused by NaCl stress by regulating the physiological and metabolic processes of rice plants, thereby enhancing the stress resistance of the plants, increasing total rice yield in salt stress conditions.

Leaf-colour modification affects canopy photosynthesis, dry-matter accumulation and yield traits in rice

Recent research has proposed to modify leaf-colour traits to improve canopy photosynthesis ( A c ) by allowing light penetration to lower layers of a dense canopy. Whether and how enhanced light penetration can really increase A c and whether leaf-colour modification influences other growth-related traits remain unclear. Canopy light and nitrogen profile parameters (i.e., the extinction coefficient for light, K L ; and for nitrogen, K N ; and their ratio, K N / K L ), A c , and agronomic yield traits were examined in nine rice genotypes comprising different genetic backgrounds and their leaf-colour variants. Compared with stay-green (G) variants, yellow-leaf (Y) variants caused larger effects on crop growth and development: altered growth duration (increased in one genetic background while decreased in the other), lower tiller number, and reduced leaf area. As with G traits, a delayed senescence at the post-flowering stage was observed in Y variants, which was associated with nitrogen dynamics in plants. Although Y variants expectedly allowed more light penetration into lower layers of the canopy (i.e., lower K L ), the leaf-nitrogen profile, and thus, the leaf photosynthetic capacity (i.e., A max ) profile, did not necessarily follow more closely the light profile. Improved A c and higher daily crop growth rate (CGR) were observed in the Y variant of one genetic background but not of the other, and the higher A c or CGR were associated with improved leaf photosynthetic nitrogen use efficiency and higher canopy K N values. The higher CGR during the grain-filling phase and resulting increased harvest index of this Y variant contributed to its greater grain productivity. Multiple regression analysis of the data of all nine genotypes indicated that the K N : K L ratio was the most important factor determining A c and CGR. Leaf-colour modification can improve A c , CGR and crop productivity only if other traits (especially N profile in the canopy) are adjusted synergistically. However, the observed diversity in phenotypic variations of multiple traits caused by leaf-colour modification implies the potential of exploiting breeding or crop management to improve rice biomass and yield. • Effects of leaf-colour modification on rice photosynthesis and yield were assessed. • Importance of relative nitrogen: light profile to canopy photosynthesis was shown. • Leaf-colour modification also altered phenological and morpho-physiological traits. • These traits can be co-exploited to maximise benefits from leaf-colour alteration.

Effect of Integrated Use of Farmyard Manure and Chemical Fertilizers on Soil Properties and Productivity of Rice in Chitwan

The effect of sole application of farm yard manure (FYM) and combined application of chemical fertilizers and FYM on soil properties and growth and yield traits of rice (Variety: Ramdhan) was studied on sandy loam soil at Rambagh, Chitwan, Nepal from June to November 2019. The seven treatments were studied in a randomized complete block design with four replications: T1: 100% recommended dose of inorganic fertilizer (RDIF) (i.e., 100:60:40 NPK kg ha-1); T2: 50% RDIF+ FYM @ 9.9 Mt ha-1; T3: 50% RDIF+ FYM @ 31.3 Mt ha-1; T4: 50% RDIF+ FYM @ 11.05 Mt ha-1; T5: FYM @ 19.83 Mt ha-1. The results indicated that combined application of chemical fertilizers and farmyard manure was found to have a significant effect on the number of effective tillers per m-2 and grain yield of rice. There was no significant interaction between thousand grain weight and sterility percent. The highest grain yield of 3,453.69 kg ha-1 and the highest number of effective tillers per m-2 (299) were found in the application of 50% RDIF+ FYM @ 31.3 Mt ha-1. The application of the highest level of FYM alone improved the soil properties. The highest values of available soil organic carbon (34.67 Mt ha-1), available soil nitrogen (1.24 Mt ha-1), and available soil phosphorus (39.57 kg ha-1) at a depth of 0–15 cm were found with the application of FYM @ 62.5 Mt ha-1. The findings of this study suggest that farmers can apply FYM @ 62.5 Mt ha-1 to improve soil properties and 50% RDIF + FYM @ 31.3 Mt ha-1 to have the higher grain yield of rice.

Assessing the genetic diversity for yield traits in rice (Oryza sativa L.) genotypes using multivariate analysis under controlled and water stress conditions

The genetic diversity of yield and yield attributing characteristics was explored in this research. In the topical study, fifty-two rice genotypes including four checks were used under three environmental conditions i.e. irrigated (IR), rainfed (RF) and terminal stage drought (TSD) conditions. The prevalence of genetic divergence was evaluated using clustering and Principal component analysis (PCA) was used to determine the relative contribution of various traits. To fulfill the aim of the study, fifty-two genotypes were grouped into three distinct and non-overlapping clusters among these 3 clusters, cluster-I was the largest with the highest number of genotypes i.e. 47, 49 and 49 under IR, RF and TSD conditions, respectively. The highest average intra-cluster distance was observed in cluster-I, also the genotypes showed high variability under all three conditions. The highest inter-cluster distance between the cluster-II and cluster-III (IR and TSD) and cluster-I and cluster-II (RF) was observed, indicated that genotypes from the group should be considered for direct use as parents in hybridization programme to produce high yield. Only five of the 13 principal components (PCs) have been considered in the study based on the Eigen values and variability criteria. From the complex matrix it was revealed that the first-PC accounted for the highest variability. Genotypes which fall under a common PC were observed to be the most important factor for grain yield.

Genetic Association between Blast Resistance and Yield Traits in Rice Detected Using a High-Density Bin Map

Avoiding linkage drag of the resistance genes will facilitate the use of gene resources for rice breeding. This study was conducted to confirm the avoidance of linkage drag due to Pi26 and Pi25 blast resistance genes, and to analyze the association of Pi26, Pi25, Pib and Pita with quantitative trait loci (QTL) for yield traits. A recombinant inbred line population was derived from an indica rice cross Dan 71/Zhonghui 161. A linkage map consisting of 1219 bin markers, 22 simple sequence repeats and five gene markers was constructed. A total of 75 QTL were identified, including 2 for leaf blast resistance and 73 for eight yield traits. The two QTL for blast resistance were closely linked and located in the Pi26 and Pi25 regions, explaining 69.06 and 12.73% of the phenotypic variance, respectively. In a region covering Pi26 and Pi25, QTL were detected for grain yield and its key components. The alleles for enhancing blast resistance and grain yield were all from Dan 71. Not only was the linkage drag due to Pi26 and Pi25 avoided, but the results also indicate that these resistance genes may be used for simultaneously enhancing blast resistance and grain yield in rice. In the Pib and Pita regions, QTL was not detected for blast resistance, but was for yield traits. In each region, the allele for improving trait performance was derived from the parent carrying the resistance allele. In addition, four QTL clusters for grain weight and size, qGL4/qGW4.1, qGL11.2/qRLW11, qTGW11/qGW11 and qGL12/qGW12/qRLW12, were shown to be promising candidates for map-based cloning.

The power of selection: Dissecting phenotypic plasticity and linkage drag underlying yield traits of rice (Oryza sativa) using selective introgression

AbstractThe power of selection and phenotypic plasticity of seven rice grain yield (GY) traits was dissected using DNA markers and 226 Minghui86 introgression lines (ILs) phenotyped across four contrast environments of long‐day versus short‐day and drought versus irrigated conditions. Linkage mapping identified 77 main‐effect quantitative trait loci (QTLs) plus 15 groups of epistatic QTLs affecting the GY traits. By characterizing genomic introgression patterns of the donor alleles in ILs selected for high‐ and low‐trait values based on replicated progeny testing across each of the four environments and for high‐ and low‐GY across nine different environmental scenarios, 246 QTLs affecting the seven yield traits were identified. Genetic drag from tight repulsive linkage of genes with opposite effects on the same traits was detected in 45 cases involving 90 (35.8%) QTLs, indicating its wide presence in superior Chinese hybrid parents. The demonstrated selective introgression strategy, including the developed ILs plus the genetic information on the associations of introgressed donor alleles with the yield traits in the ILs would provide a useful platform for future breeding by design.

Impact of Government Policies on Seed Innovation in China

Seed innovation is of great importance for more sustainable agriculture and food systems. Using data on nationally approved rice varieties and farmers’ adopted varieties, this study examined rice varietal trait changes in China over the past four decades and explored the impact of national crop varietal approval policies on approved rice traits as well as the effect of seed subsidies on adopted rice trait changes. The results showed that the yield of approved varieties and adopted varieties showed an upward trend over the past decades, and the yield of approved varieties was slightly higher than that of adopted varieties in most years. The rice quality of approved rice varieties showed a trend of continuous improvement but the adopted varieties showed a downward trend. The disease resistance of the approved varieties failed to show an increasing trend overall while the adopted varieties remained unchanged. National crop variety approval policies seemed to exert a significant positive impact on approved rice yield traits but exert a negative influence on disease resistance. Subsidies for superior seed varieties significantly increased adopted rice quality but decreased yield. The results suggest that national crop variety approval policies are the gatekeeper of improved rice, so the government can improve the policies to more meet farmers’ and consumers’ needs.