Grain size is a quantitative trait that is controlled by multiple genes. It is not only a yield trait, but also an important appearance quality of rice. In addition, grain size is easy to be selected in evolution, which is also a significant trait for studying rice evolution. In recent years, many quantitative trait loci (QTL)/genes for rice grain size were isolated by map-based cloning or genome-wide association studies, which revealed the genetic and molecular mechanism of grain size regulation in part. Here, we summarized the QTL/genes cloned for grain size and the regulation mechanism with a view to provide the theoretical basis for improving rice yield and breeding superior varieties.

Lesion mimic mutants refer to a class of mutants that naturally form necrotic lesions similar to allergic reactions on leaves in the absence of significant stress or damage and without being harmed by pathogens. Mutations in most lesion mimic genes, such as OsACL-A2 and OsSCYL2, can enhance mutants’ resistance to pathogens. Lesion mimic mutants are ideal materials for studying programmed cell death (PCD) and plant defense mechanisms. Studying the genes responsible for the rice disease-like phenotype is of great significance for understanding the disease resistance mechanism of rice. In this paper, the nomenclature, occurrence mechanism, genetic characteristics, regulatory pathways, and the research progress on the cloning and disease resistance of rice lesion mimic mutant genes were reviewed, in order to further analyze the various lesion mimic mutants of rice. The mechanism lays a theoretical foundation and provides a reference for rice breeding.

Anther culture (AC) is a valuable technique in rice breeding. However, the genetic mechanisms underlying anther culturability remain elusive, which has hindered its widespread adoption in rice breeding programs. During AC, microspores carrying favorable alleles for AC are selectively regenerated, leading to segregation distortion (SD) of chromosomal regions linked to these alleles in the doubled haploid (DH) population. Using the AC method, a DH population was generated from the japonica hybrid rice Shenyou 26. A genetic map consisting of 470 SNPs was constructed using this DH population, and SD analysis was performed at both the single- and two-locus levels to dissect the genetic basis underlying anther culturability. Five segregation distortion loci (SDLs) potentially linked to anther culturability were identified. Among these, SDL5 exhibited an overrepresentation of alleles from the female parent, while SDL1.1, SDL1.2, SDL2, and SDL7 displayed an overrepresentation of alleles from the male parent. Furthermore, six pairs of epistatic interactions (EPIs) that influenced two-locus SDs in the DH population were discovered. A cluster of genetic loci, associated with EPI-1, EPI-3, EPI-4, and EPI-5, overlapped with SDL1.1, indicating that the SDL1.1 locus may play a role in regulating anther culturability via both additive and epistatic mechanisms. These findings provide valuable insights into the genetic control of anther culturability in rice and lay the foundation for future research focused on identifying the causal genes associated with anther culturability.

The development of a new salt–alkaline-tolerant hybrid japonica rice is crucial for enhancing japonica rice supply and ensuring national food security. Utilizing molecular marker-assisted selection (MAS) technology combining Kompetitive Allele-Specific PCR (KASP) markers and a gene breeding chip, the salt-tolerant gene SKC1 was introgressed into a rice genotype Fan 14. This led to the development of Shenyanhui 1, a new high-quality, strongly heterotic, and salt-tolerant japonica restorer line. Subsequently, the high-quality, salt-tolerant japonica three-line hybrid rice variety Shenyanyou 1 was developed by crossing the BT-type japonica cytoplasmic male sterile (CMS) line Shen 21A with the restorer line Shenyanhui 1. Shenyanyou 1 carries the major salt tolerance gene SKC1, exhibiting excellent salt tolerance with seedling stage salt tolerance reaching level 5. Under precise salt tolerance evaluation throughout its growth cycle, Shenyanyou 1 achieved a yield of 3640.5 kg/hm², representing an extremely significant increase of 20.7% over the control variety Yandao 21. Shenyanyou 1 exhibits superior grain quality, meeting the Grade 3 high-quality rice standards issued by the Ministry of Agriculture. Shenyanyou 1 has good comprehensive resistance, aggregating rice blast resistance genes such as Pi2, Pita, Pizt and LHCB5, bacterial blight resistance genes Xa26/Xa3, stripe blast resistance gene STV11, semi-dwarf gene Sdt97, nitrogen-efficient utilization gene NRT1.1B, the light repair activity enhancement gene qUVR-10, the cold resistance gene qLTG3-1, and the iron tolerance gene OsFRO1. It has good resistance to biotic and abiotic stresses. This paper details the breeding process, key agronomic traits, salt tolerance, yield performance, and grain quality characteristics of Shenyanyou 1.

Fusarium fujikuroi is the primary causal agent of rice bakanae disease, which can lead to substantial yield losses. Developing a rapid, highly specific, and accurate method for detecting F. fujikuroi is crucial for effective surveillance, prevention, and control of rice bakanae disease. In this study, a novel detection assay, RPA-Cas12a-F, was developed by integrating recombinase polymerase amplification (RPA) and Cas12a for the detection of F. fujikuroi. This assay demonstrated a limit of detection (LOD) of 1 copy/μL of reference plasmid or 0.1 fg/μL of F. fujikuroi genomic DNA (gDNA). Furthermore, to enable on-site detection, the RPA-Cas12a technique was combined with a lateral flow strip (LFS) for visual readout, thereby developing the RPA-Cas12a-LFS assay. The LOD of the RPA-Cas12a-LFS assay was 1000 copies/μL of plasmid or 10 fg/μL of F. fujikuroi gDNA. The RPA-Cas12a-based assays developed in this study enable rapid, highly accurate, sensitive, and specific detection of F. fujikuroi, making them a promising tool for on-site detection without the need for expensive equipment and time-consuming methodologies.

Chloroplasts are critical organelles for photosynthesis and play significant roles in plant growth and metabolism. High temperature is one of abiotic stresses affecting the growth and development of plants, involving chlorophyll biosynthesis and chloroplast development. It is well known that the methyl erythritol 4-phosphate (MEP) pathway is vital to photosynthesis and plant growth, and 1-deoxy-D-xylulose-5-phosphate synthase (DXS) is the enzyme that catalyze the first step of the MEP pathway. Although DXS has been widely studied in microbes and plants, no DXS gene has been identified in rice. Here, a novel thermo-sensitive chlorophyll-deficient 5 (tscd5) mutant was isolated in rice with decreased chlorophyll contents, impaired chloroplasts, and albino leaves at high temperature (35 °C). Fine mapping and DNA sequencing of TSCD5 found a missense mutation (G to A) in the sixth exon of LOC_Os05g33840 in tscd5. The TSCD5 gene encodes a 1-deoxy-D-xylulose-5-phosphate synthase 1 (OsDXS1) localized in chloroplast. Complementation tests and overexpression assay demonstrated that the mutation in LOC_Os05g33840 caused the tscd5 phenotype. qRT-PCR of TSCD5 showed it was constitutively expressed in all tissues, and its transcript amounts were reduced in tscd5 under high temperature. Here, TSCD5 is verified to be crucial to chloroplast development under high temperature in rice, which may facilitate the elucidation of the molecular mechanisms which underlie acclimation to high temperature stress in plants.