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[学术文献 ] Creation of Two-Line Fragrant Glutinous Hybrid Rice by Editing the Wx and OsBADH2 Genes via the CRISPR/Cas9 System 进入全文
International Journal of Molecular Sciences
Global food security has benefited from the development and promotion of the two-line hybrid rice system. Excellent eating quality determines the market competitiveness of hybrid rice varieties based on achieving the fundamental requirements of high yield and good adaptability. Developing sterile and restorer lines with improved quality for two-line hybrid breeding by editing quality genes with clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 is an efficient and practical alternative to the lengthy and laborious process of conventional breeding to improve rice quality. We edited Wx and OsBADH2 using CRISPR/Cas9 technology to produce both homozygous male sterile mutant lines and homozygous restorer mutant lines with Cas9-free. These mutants have a much lower amylose content while having a significantly higher 2-acetyl-1-pyrroline aroma content. Based on this, a fragrant glutinous hybrid rice was developed without too much effect on most agronomic traits. This study demonstrates the use of CRISPR/Cas9 in creating two-line fragrant glutinous hybrid rice by editing the components of the male sterile and the restorative lines.
[学术文献 ] Breeding of the Long-Grain Restorer of Indica-Japonica Hybrid Rice by Using the Genetic Effects of Grain Shape QTLs 进入全文
Agronomy
Grain shape improvement, which determines grain yield, quality traits and commercial value, is an extremely important aspect of rice breeding. Grain size is controlled by multiple genes, and Maker Assistant Selection (MAS) breeding is effective for breeders in developing stable and efficient markers to aggregate these genes in order to speed up the selection of new lines with desirable traits during the breeding process. In this study, functional markers were developed based on the sequence differences of five grain-shaped genes (GL7, GW6a, GS6, GW5 and TGW6) between the long-grain japonica rice variety Zhendao and the indica-japonica restorer R2027. We then constructed a population of recombinant inbred lines (RILs) based on their cross. The newly designed functional markers were used to genotype grain-size genes, and a genetic effect analysis was conducted to screen high-quality long-grain restorers. Our results reveal diverse effects of different genes on grain size, and the five genotypes were distributed in the 36 selected BC1F8 lines. Specifically, gw5 positively regulates grain width and 1000-grain weight, gl7 and gs6 positively regulate grain length but negatively regulate grain width and 1000-grain weight, tgw6 positively regulates grain length and gw6a positively regulates 1000-grain weight. The most outstanding outcome is that 5 of the 36 lines achieved in this study showing an excellent performance of long grain and yield characters are ideal materials not only for studying the interaction and genetic effects between polygenes but also as restorers or donors for dominant genes in indica-japonica hybrid rice breeding.
[学术文献 ] Nitrogen Use Traits of Different Rice for Three Planting Modes in a Rice-Wheat Rotation System 进入全文
Agriculture
At present, there is a limited understanding of nitrogen (N) accumulation, translocation, and utilization in different types of rice grown using different planting methods in a rice–wheat rotation system. Systematic experiments were conducted with six rice cultivars, including two japonica-indica hybrids (JIHR), two japonica conventional rice (JCR) cultivars, and two indica hybrid rice (IHR) cultivars, to study the effects on N use of plants in three transplanting modes: (1) the pothole seedling machine transplanting mode (PM), (2) the carpet seedling machine transplanting mode (CM), and (3) the mechanical direct seeding mode (DM). Results showed that at stem elongation stage, for N content and uptake, the planting methods were ranked in the order PM < CM < DM, and at heading and maturity the order was PM > CM > DM. After stem elongation the rankings for N accumulation, ratio of N accumulation to total N, and N uptake rate were PM > CM >DM. Thus, on the basis of a certain amount of N accumulation in the early growth phase, increasing the N uptake rate and N accumulation in the middle and late growth phases are ways to increase total N uptake for the PM and CM modes compared to DM. In addition, the PM/JIHR treatment had the highest N uptake at maturity. The N contents of leaves, stem-sheaths, and panicles at heading and maturity for the three planting modes were ranked PM > CM > DM. Moreover, the N translocation amount, apparent N translocation rate, and translocation conversion rate of leaves under PM were significantly higher than for CM and DM, which would increase N accumulation in the grain. The N uptake per 100 kg grain and the partial factor productivity of applied N under PM were larger than for CM and DM, but the N use efficiency of grain yield and biomass were smaller for PM than for CM and DM. In conclusion, rice grown using PM, especially JIHR, had higher total N uptake and N utilization compared to the CM and DM modes, and cultivation measures to improve the N use efficiency of grain yield and biomass could be appropriately applied to further improve N use in a rice–wheat rotation system.
[学术文献 ] Optimized Management Practices Synergistically Improved Grain Yield and Nitrogen Use Efficiency by Enhancing Post-Heading Carbon and Nitrogen Metabolism in Super Hybrid Rice 进入全文
Agronomy
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.
[学术文献 ] Genomic revolution of US weedy rice in response to 21st century agricultural technologies 进入全文
COMMUNICATIONS BIOLOGY
Weedy rice is a close relative of cultivated rice that devastates rice productivity worldwide. In the southern United States, two distinct strains have been historically predominant, but the 21(st) century introduction of hybrid rice and herbicide resistant rice technologies has dramatically altered the weedy rice selective landscape. Here, we use whole-genome sequences of 48 contemporary weedy rice accessions to investigate the genomic consequences of crop-weed hybridization and selection for herbicide resistance. We find that population dynamics have shifted such that most contemporary weeds are now crop-weed hybrid derivatives, and that their genomes have subsequently evolved to be more like their weedy ancestors. Haplotype analysis reveals extensive adaptive introgression of cultivated alleles at the resistance gene ALS, but also uncovers evidence for convergent molecular evolution in accessions with no signs of hybrid origin. The results of this study suggest a new era of weedy rice evolution in the United States.
[学术文献 ] Transcriptome Analyses Indicate Significant Association of Increased Non-Additive and Allele-Specific Gene Expression with Hybrid Weakness in Rice (Oryza sativa L.) 进入全文
LIFE-BASEL
The heterosis in hybrid rice is highly affected by the environment and hybrid weakness occurs frequently depending on the genotypes of the hybrid and its parents. Hybrid weakness was also observed in our field experiments on nine rice hybrids produced by 3 x 3 incomplete diallel crosses. Among the nine hybrids, five displayed mid-parent heterosis (MPH) for grain yield per plant, while four showed mid-parent hybrid weakness (MPHW). A sequencing analysis of transcriptomes in panicles at the seed-filling stage revealed a significant association between enhanced non-additive gene expression (NAE) and allele-specific gene expression (ASE) with hybrid weakness. High proportions of ASE genes, with most being of mono-allele expression, were detected in the four MPHW hybrids, ranging from 22.65% to 45.97%; whereas only 4.80% to 5.69% of ASE genes were found in the five MPH hybrids. Moreover, an independence test indicated that the enhancements of NAE and ASE in the MPHW hybrids were significantly correlated. Based on the results of our study, we speculated that an unfavorable environment might cause hybrid weakness by enhancing ASE and NAE at the transcriptome level.
