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Summary: Grain yield is one of the most important and complex trait for genetic improvement in crops; it is known to be controlled by a number of genes known as quantitative trait loci (QTLs). In the past decade, many yield‐contributing QTLs have been identified in crops. However, it remains unclear whether those QTLs confer the same yield performance in different genetic backgrounds. Here, we performed CRISPR/Cas9‐mediated QTL editing in five widely‐cultivated rice varieties and revealed that the same QTL can have diverse, even opposing, effects on grain yield in different genetic backgrounds. [ABSTRACT FROM AUTHOR]

Summary Panicle architecture is one of the most important agronomical traits that directly contribute to grain yield in rice ( Oryza sativa L.). We report herein an in-depth characterization of two allelic larger panicle ( lp) mutants that show significantly increased panicle size as well as improved plant architecture. Morphological analyses reveal that panicles of two mutants produced more inflorescence branches, especially the primary branches, and contained more grains. Moreover, mutant plants also display more lodging resistance than the wild type. The grain yield per plant in mutants is also increased, suggesting that mutant plants have useful potential for high grain yield in rice breeding. Map-based cloning reveals that LARGER PANICLE (LP) encodes a Kelch repeat-containing F-box protein. RNA in situ hybridization studies display that LP expression was enriched in the branch primordial region. Subcellular localization analyses demonstrate that LP is an endoplasmic reticulum (ER) localized protein, suggesting that LP might be involved in ER-associated protein degradation (ERAD). Using yeast two-hybrid assay and bimolecular fluorescence complementation analysis, we confirm that LP is an F-box protein and could interact with rice SKP1-like protein in an F-box domain-dependent manner. Quantitative real-time PCR results show that OsCKX2, which encodes cytokinin oxidase/dehydrogenase, is down-regulated evidently in mutants, implying that LP might be involved in modulating cytokinin level in plant tissues. These results suggest that LP plays an important role in regulating plant architecture, particularly in regulating panicle architecture, thereby representing promising targets for genetic improvement of grain production plants. [ABSTRACT FROM AUTHOR]

Rice seed size is an important agronomic trait in determining the yield potential, and four seed size related genes ( GS3, GW2, qSW5/ GW5 and GIF1) have been cloned in rice so far. However, the relationship among these four genes is still unclear, which will impede the process of gene pyramiding breeding program to some extent. To shade light on the relationship of above four genes, gene expression analysis was performed with GS3-RNAi, GW2-RNAi lines and CSSL of qSW5 at the transcriptional level. The results clearly showed that qSW5 and GW2 positively regulate the expression of GS3. Meanwhile, qSW5 can be down-regulated by repression of GW2 transcription. Additionally, GIF1 expression was found to be positively regulated by qSW5 but negatively by GW2 and GS3. Moreover, the allelic effects of qSW5 and GS3 were detailedly characterized based on a natural population consisting of 180 rice cultivars. It was indicated that mutual interactions exist between the two genes, in which, qSW5 affecting seed length is masked by GS3 alleles, and GS3 affecting seed width is masked by qSW5 alleles. These findings provide more insights into the molecular mechanisms underlying seed size development in rice and are likely to be useful for improving rice grain yield. [ABSTRACT FROM AUTHOR]

Improving grain quality is an important goal in breeding new elite rice varieties, requiring effective tools for the identification of target genotypes. Molecular marker-aided selection (MAS), combined with conventional breeding approaches, enables us to precisely identify the individual genotypes that are associated with different grain quality features, which can dramatically improve the breeding efficiency. However, to date, the number of molecular markers used in MAS for grain quality improvement is still somewhat limited. In this study, based on our previous study that rice grain quality is strongly associated with starch synthesis in the endosperm, we developed 51 gene-tagged molecular markers according to sequence variations in 18 starch synthesis-related genes from 16 typical rice cultivars. These markers can discriminate the different alleles among rice germplasms. These novel markers will provide effective tools in improving grain quality via the breeding new elite rice varieties. [ABSTRACT FROM AUTHOR]

The semidwarf gene sd-g which has been used in indica rice breeding in southern China is a new one, nonallelic to sd-1. To map sd-g, an F2 population derived from the cross between Xinguiaishuangai and 02428 was constructed. The sd-g was roughly mapped between two microsatellite markers RM440 and RM163, with genetic distances of 0.5 and 2.5 cM, respectively. Then nine new polymorphic microsatellite markers were developed in this region. The sd-g was further mapped between two microsatellite markers SSR5-1 and SSR5-51, with genetic distances of 0.1 and 0.3 cM, respectively, while cosegregated with SSR418. A BAC contig was found to span the sd-g locus, the region being delimited to 85 kb. This result was very useful for cloning of the sd-g gene. [ABSTRACT FROM AUTHOR]