Background: Flag leaf is the most essential organ for photosynthesis in rice and its size plays an important role in rice breeding for ideal plant-type. Flag leaf size affect photosynthesis to a certain extent, thereby influencing rice production. Several genes controlling leaf size and shape have been identified with mutants. Although a number of quantitative trait loci (QTLs) for leaf size and shape have been detected on 12 chromosomes with different populations of rice, few of them were cloned. Results: The pair-wise correlation analysis was conducted on length, width and length-width ratio of the flag leaf, and yield per plant in the core recombinant inbred lines of Liang-You-Pei-Jiu (LYP9) developed in Hainan and Hangzhou. There were significant correlations among the three flag leaf size and shape traits. Interestingly, a positive correlation was found between flag leaf width and yield per plant. Based on the high-resolution linkage map we constructed before, 43 QTLs were detected for three flag leaf size and shape traits and yield per plant, among which 31 QTLs were unreported so far. Seven QTLs were identified common in two environments. And qFLW7.2, a new major QTL for flag leaf width, was fine mapped within 27.1 kb region on chromosome 7. Both qFLW7.2 and qPY7 were located in the interval of 45.30 ~ 53.34 cM on chromosome 7, which coincided with the relationship between yield per plant (PY) and flag leaf width (FLW). Conclusion: qFLW7.2, which explained 14% of the phenotypic variation, increased flag leaf width with 93–11 allele. Two candidate genes were selected based on sequence variation and expression difference between two parents, which facilitated further QTL cloning and molecular breeding in super rice.

Background: Flowering time, which is often associated with the length of the growth period in rice, determines the adaptability of a plant to various environments. However, little is known about how flowering-time genes affect panicle development and yield formation potential in rice after inducing the transition from vegetative growth to reproductive growth. Results: To explore the relationship between floral induction and yield formation and the molecular mechanism of panicle development in rice, a novel mutant, ghd10, was identified from japonica variety Wuyunjing 7 plants subjected to ethyl methane sulfonate (EMS) treatment. The ghd10 mutant exhibited delayed flowering time, tall stalks and increased panicle length and primary branch number. Map-based cloning revealed that Ghd10 encodes a transcription factor with Cys-2/His-2-type zinc finger motifs. Ghd10 is orthologous to INDETERMINATE1 (ID1), which promotes flowering in maize (Zea mays) and is identical to the previously cloned genes Rice Indeterminate1 (RID1), Early heading date2 (Ehd2) and OsId1. Transient expression analysis of the Ghd10-GFP fusion protein in tobacco mesophyll cells showed that this protein is expressed in the nucleus. Ghd10 mRNA accumulated most abundantly in developing leaves and panicle structures, but rarely in roots. Expression analysis revealed that the expression levels of Ehd1, Hd1, RFT1, Hd3a and OsMADS15 decreased dramatically under both short-day and long-day conditions in ghd10. Conclusion: These results indicate that Ghd10, which encodes a promoter of flowering, influences plant height and panicle development by regulating the expression levels of some flowering-related genes, such as Ehd1, Hd1, OsMADS15 and others. The ghd10 allele is a useful resource for improvement of panicle traits in rice grown in tropical and low-latitude areas.

Hybrid rice has contributed substantially to the improvement of grain production worldwide, yet its poor cooking and tasting characteristics have long been recognized. In this study, 132 recombinant inbred lines derived from LYPJ were used to identify quantitative trait loci (QTLs) for 12 cooking traits with the high-density SNP linkage map recently developed by our team. We identified 17 QTLs on chromosomes 1, 2, 4, 5, 6, 7, 8, 9 and 11, which accounted for 7.50% to 23.50% of the phenotypic variations. A novel major QTL qBGL7 for boiled grain length was further fine-mapped to an interval of 440 Kb between the two markers RM21906 and gl3 using a BC₃F₂ population. Two near-isogenic lines with extreme boiled grain length, GX5-176 and GX5-101, could be directly used in improving cooking quality. We also identified a QTL for soaked grain width expansion rate, qSGWE6, in the Wx gene region on chromosome 6. The Wx differential regulation coincided with sequential variation between the two parents. Our work offered a theoretical basis for molecular breeding of high-quality hybrid rice.

Summary: Roots act as the plants' primary determinants of the uptake of water and nutrients, while the root structure largely depends on the repeated formation of new lateral roots (LR). Lateral root primordium (LRP) formation defines the organization and function of LRs. Therefore, lateral root formation is quite related to proper LRP morphogenesis to a great extent. Here, we identified the Arabidopsis TERMINAL FLOWER1 (TFL1) ortholog gene Dt1, which mediates soybean LRP development. The dt1 knock‐out mutants showed reduced LRs with decreased LRPs. Further experiments proved that Dt1 interacted with the homeodomain‐leucine zipper (HD‐Zip) I family transcription factor HB40 to regulate Cell Division Control protein 48 (CDC48) expression and thus affect soybean LRP development. In summary, this study identified the Dt1‐HB40‐CDC48 regulatory modules to intricately control LRP development.