Discovery of a Novel Induced Polymorphism in SD1 Gene Governing Semi-Dwarfism in Rice and Development of a Functional Marker for Marker-Assisted Selection

Genomic prediction and QTL analysis for grain Zn content and yield in Aus-derived rice populations

Zinc (Zn) biofortification of rice can address Zn malnutrition in Asia. Identification and introgression of QTLs for grain Zn content and yield (YLD) can improve the efficiency of rice Zn biofortification. In four rice populations we detected 56 QTLs for seven traits by inclusive composite interval mapping (ICIM), and 16 QTLs for two traits (YLD and Zn) by association mapping. The phenotypic variance (PV) varied from 4.5% (qPN 4.1 ) to 31.7% (qPH 1.1 ). qDF 1.1 , qDF 7.2 , qDF 8.1 , qPH 1.1 , qPH 7.1 , qPL 1.2 , qPL 9.1, qZn 5.1 , qZn 5.2 , qZn 6.1 and qZn 7.1 were identified in both dry and wet seasons; qZn 5.1 , qZn 5.2 , qZn 5.3, qZn 6.2, qZn 7.1 and qYLD 1.2 were detected by both ICIM and association mapping. qZn 7.1 had the highest PV (17.8%) and additive effect (2.5 ppm). Epistasis and QTL co-locations were also observed for different traits. The multi-trait genomic prediction values were 0.24 and 0.16 for YLD and Zn respectively. qZn 6.2 was co-located with a gene (OsHMA2) involved in Zn transport. These results are useful for Zn biofortificatiton of rice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13562-024-00886-0.

Important Factors Controlling Gibberellin Homeostasis in Plant Height Regulation

Plant height is an important agronomic trait that is closely associated with crop yield and quality. Gibberellins (GAs), a class of highly efficient plant growth regulators, play key roles in regulating plant height. Increasing reports indicate that transcriptional regulation is a major point of regulation of the GA pathways. Although substantial knowledge has been gained regarding GA biosynthetic and signaling pathways, important factors contributing to the regulatory mechanisms homeostatically controlling GA levels remain to be elucidated. Here, we provide an overview of current knowledge regarding the regulatory network involving transcription factors, noncoding RNAs, and histone modifications involved in GA pathways. We also discuss the mechanisms of interaction between GAs and other hormones in plant height development. Finally, future directions for applying knowledge of the GA hormone in crop breeding are described.

Upgrading the genome of an elite japonica rice variety Kongyu 131 for lodging resistance improvement

Developing a new rice variety requires tremendous efforts and years of input. To improve the defect traits of the excellent varieties becomes more cost and time efficient than breeding a completely new variety. Kongyu 131 is a high-performing japonica variety with early maturity, high yield, wide adaptability and cold resistance, but the poor-lodging resistance hinders the industrial production of Kongyu 131 in the Northeastern China. In this study, we attempted to improve the lodging resistance of Kongyu 131 from perspectives of both gene and trait. On the one hand, by QTL analysis and fine mapping we discovered the candidate gene loci. The following CRISPR/Cas9 and transgenic complementation study confirmed that Sd1 dominated the lodging resistance and favourable allele was mined for precise introduction and improvement. On the other hand, the Sd1 allelic variant was identified in Kongyu 131 by sequence alignment, then introduced another excellent allelic variation by backcrossing. Then, the two new resulting Kongyu 131 went through the field evaluation under different environments, planting densities and nitrogen fertilizer conditions. The results showed that the plant height of upgraded Kongyu 131 was 17%-26% lower than Kongyu 131 without penalty in yield. This study demonstrated a precise and targeted way to update the rice genome and upgrade the elite rice varieties by improving only a few gene defects from the perspective of breeding.

Harnessing hormone gibberellin knowledge for plant height regulation

Harnessing hormone GA knowledge is a potential means to develop plant height ideotypes. Plant height holds significance for natural beauty and agricultural revolution. The increased grain productivity during the Green Revolution of the 1960s is partly attributed to the reshaping of plant stature, which is conferred by changes in phytohormone gibberellin (GA) metabolism or signaling. GA fine-tunes multiple aspects of biological events and plays a pivotal role in plant height determinant. Harnessing hormone GA knowledge is a potential means to develop ideal plant height to meet the future demand. Here, we present an overview of characterized GA pathway genes for plant height regulation. Novel alleles of Green Revolution genes sd1 and Rht are specially delineated. Through interactome analysis, we uncover GA20ox and GA3ox family members as central hub modulators of GA pathway. Empowered by GA knowledge, we suggest ways towards design breeding of plant height ideotypes through harnessing the alterations of GA cascade. We highlight the utility of genome editing to generate weak alleles to circumvent side effects of GA pathway perturbation.

Untargeted Metabolite Profiling of Specialty Rice Grains Using Gas Chromatography Mass Spectrometry

With-ever increasing demand food grains for the increasing population, it has also increased the importance of quality rice with nutritional and therapeutic properties. The quality of rice includes nutritional value, therapeutic properties, and further generation of aroma. Initial studies on sensory analysis using potassium hydroxide (1.7% KOH) identified the presence of a distinct aroma of the traditional rice cultivar Chakhao Amubi in comparison with other aromatic rice varieties were conducted. The metabolomic profiling of aromatic rice grains Chakhao Amubi, Pusa Basmati 1, and nonaromatic rice, Improved White Ponni was attempted to use gas chromatography-mass spectrometry (GC-MS). A total of fifty volatile aromatic compounds, including aromatic hydrocarbons, alkanes, alkenes, ketones, and aromatic aldehydes, have been identified. Detected compounds include six crucial volatile i.e., pentanal, hexanal, 2-pentylfuran, pyridine, (Z)-7-Decenal, and Mesitylene for distinct flavor and presence of aroma in Chakhao Amubi. The findings showed a distinct difference in the metabolic profile of Chakhao Amubi compared to Pusa Basmati 1 and Improved White Ponni. Thus, this study paved the way for a new understanding of the aromatic aspects of traditional rice germplasm and its utilization in rice breeding programs to improve the aroma, therapeutic, and nutritional characteristics of rice.

Whole Genome Sequencing and Morphological Trait-Based Evaluation of UPOV Option 2 for DUS Testing in Rice

To evaluate the application potential of high-density SNPs in rice distinctness, uniformity, and stability (DUS) testing, we screened 37,929 SNP loci distributed on 12 rice chromosomes based on whole-genome resequencing of 122 rice accessions. These SNP loci were used to analyze the DUS testing of rice varieties based on the correlation between the molecular and phenotypic distances of varieties according to UPOV option 2. The results showed that statistical algorithms and the number of phenotypic traits and SNP loci all affected the correlation between the molecular and phenotypic distances of rice varieties. Relative to the other nine algorithms, the Jaccard similarity algorithm had the highest correlation of 0.6587. Both the number of SNPs and the number of phenotypes had a ceiling effect on the correlation between the molecular and phenotypic distances of varieties, and the ceiling effect of the number of SNP loci was more obvious. To overcome the correlation bottleneck, we used the genome-wide prediction method to predict 30 phenotypic traits and found that the prediction accuracy of some traits, such as the basal sheath anthocyanin color, glume length, and intensity of the green color of the leaf blade, was very low. In combination with group comparison analysis, we found that the key to overcoming the ceiling effect of correlation was to improve the resolution of traits with low predictive values. In addition, we also performed distinctness testing on rice varieties by using the molecular distance and phenotypic distance, and we found that there were large differences between the two methods, indicating that UPOV option 2 alone cannot replace the traditional phenotypic DUS testing. However, genotype and phenotype analysis together can increase the efficiency of DUS testing.

Detection of QTLs for Plant Height Architecture Traits in Rice (Oryza sativa L.) by Association Mapping and the RSTEP-LRT Method

Plant height (PH) and its component traits are critical determinants of lodging resistance and strongly influence yield in rice. The genetic architecture of PH and its component traits were mined in two mapping populations. In the natural population composed of 504 accessions, a total of forty simple sequence repeat (SSR) markers associated with PH and its component traits were detected across two environments via association mapping. Allele RM305-210 bp on chromosome 5 for PH had the largest phenotypic effect value (PEV) (−51.42 cm) with a reducing effect. Allele RM3533-220 bp on chromosome 9 for panicle length and allele RM264-120 bp on chromosome 8 for the length of upper first elongated internode (1IN) showed the highest positive PEV. Among the elongated internodes with negative effects being desirable, the allele RM348-130 bp showed the largest PEV (−7.48 cm) for the length of upper second elongated internode. In the chromosome segment substitution line population consisting of 53 lines, a total of nine QTLs were detected across two environments, with the phenotypic variance explained (PVE) ranging 10.07–28.42%. Among the detected QTLs, q1IN-7 explained the largest PVE (28.42%) for the 1IN, with an additive of 5.31 cm. The favorable allele RM257-125 bp on chromosome 9 for the 1IN increasing was detected in both populations. The favorable alleles provided here could be used to shape PH architecture against lodging.

Genome-Wide and Exome-Capturing Sequencing of a Gamma-Ray-Induced Mutant Reveals Biased Variations in Common Wheat

Induced mutagenesis is a powerful approach for the creation of novel germplasm and the improvement of agronomic traits. The evaluation of mutagenic effects and functional variations in crops is needed for breeding mutant strains. To investigate the mutagenic effects of gamma-ray irradiation in wheat, this study characterized genomic variations of wheat early heading mutant (eh1) as compared to wild-type (WT) Zhongyuan 9 (ZY9). Whole-genome resequencing of eh1 and ZY9 produced 737.7 Gb sequencing data and identified a total of 23,537,117 homozygous single nucleotide polymorphism (SNP) and 1,608,468 Indel. Analysis of SNP distribution across the chromosome suggests that mutation hotspots existed in certain chromosomal regions. Among the three subgenomes, the variation frequency in subgenome D was significantly lower than in subgenomes A and B. A total of 27.8 Gb data were obtained by exome-capturing sequencing, while 217,948 SNP and 13,554 Indel were identified. Variation annotation in the gene-coding sequences demonstrated that 5.0% of the SNP and 5.3% of the Indel were functionally important. Characterization of exomic variations in 12 additional gamma-ray-induced mutant lines further provided additional insights into the mutagenic effects of this approach. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) analysis suggested that genes with functional variations were enriched in several metabolic pathways, including plant-pathogen interactions and ADP binding. Kompetitive allele-specific PCR (KASP) genotyping with selected SNP within functional genes indicated that 85.7% of the SNPs were polymorphic between the eh1 and wild type. This study provides a basic understanding of the mechanism behind gamma-ray irradiation in hexaploid wheat.