Abstract
Grain weight and size are important traits determining grain yield and influencing grain quality in rice. In a previous study, a quantitative trait locus controlling thousand-grain weight (TGW) in rice, qTGW10-20.8, was mapped in a 70.7 kb region on chromosome 10. Validation of the candidate gene for qTGW10-20.8, OsMADS56 encoding a MADS-box transcription factor, was performed in this study. In a near-isogenic line (NIL) population segregated only at the OsMADS56 locus, NILs carrying the OsMADS56 allele of IRBB52 were 1.9% and 2.9% lower in TGW than NILs carrying the OsMADS56 allele of Teqing in 2018 and 2020, respectively. Using OsMADS56 knock-out mutants and overexpression transgenic plants, OsMADS56 was validated as the causal gene for qTGW10-20.8. Compared with the recipients, the TGW of the knock-out mutants was reduced by 6.0–15.0%. In these populations, decreased grain weight and size were associated with a reduction in the expression of OsMADS56. In transgenic populations of OsMADS56 driven by a strong constitutive promoter, grain weight and size of the positive plants were significantly higher than those of the negative plants. Haplotype analysis showed that the Teqing-type allele of OsMADS56 is the major type presented in cultivated rice and used in variety improvement. Cloning of OsMADS56 provides a new gene resource to improve grain weight and size through molecular design breeding.
Highlights
Rice (Oryza sativa L.) is one of the most important food crops in China
Genetic Effect of OsMADS56 in near-isogenic line (NIL) Populations Derived from Teqing/IRBB52
The first experiment to confirm whether OsMADS56 is the target gene of qTGW1020.8 was conducted using two populations having the same segregating region that only involved one gene, OsMADS56 (Figure 1A)
Summary
Rice (Oryza sativa L.) is one of the most important food crops in China. Of the population relies on rice as the staple food. Thousand-grain weight (TGW) is one of the most important determinants of rice grain yield and is determined by grain length (GL), grain width (GW) and grain thickness. GL and GW are important indicators for evaluating the appearance quality of rice. Cloning of quantitative trait loci (QTLs) for grain weight and size has an important role in the molecular breeding of high-yield superior-quality rice varieties. Causal genes for 22 QTLs controlling grain weight and size have been cloned. Two of the genes regulated GL and GW without affecting TGW, including GL7/GW7 [1,2]
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