Abstract: Using the elite germplasm resources collected by the laboratory, B91 and B233 were used to analyze the key phenotypic traits affecting grain weight, and the genetic sites and candidate genes involved in grain weight correlation were explored to further understand the genetic basis of multi-gene regulation of grain traits, for applying it in the improvement of germplasm resources. Two indica parents B91 and B233 and the crossbreeding F₂ population were used as research materials. The scanning morphological observations of B91 and B233 grain hulls and endosperm were carried out to determine the parenteral filling rate. QTL-seq analysis was performed using the F₂ segregating population constructed by B91 and B233, and the grain weight candidate gene was further screened by annotating gene expression position and predictive function. The results showed that according to scanning electron microscopy of grain hulls and endosperm, the difference between B233 and B91 grain length, grain width and grain thickness was determined by cell size and cell number, and the grain fullness of B233 was worse than B91. Through the comparison of grouting parameters, the initial growth potential of B233, active grouting time, maximum grouting rate and other indicators were all greater than B91. A total of 430 762 effective SNP locis were obtained from QTL-seq analysis and a total of 8 QTLs were found on 6 chromosomes. This study mainly focused on the five QTLs in the positive threshold region, and screened SNP sites with △(SNP-index)>0.7 in the QTL sites of the positive threshold region. In the positive threshold region, 23 SNP mutations genes and 11 Indel mutation genes were selected, and six candidate genes for regulating grain weight traits were screened based on the NCBI website for transcriptional expression analysis and gene function prediction of the annotated genes. In the six candidate genes, the gene Os04g0617600, Os04g0619600 encoded protein acts as a protein kinase or transcriptional regulator; Os04g0624600, Os04g0631000 regulated the synthesis and decomposition of carbohydrates; Os04g0653100 regulated the transport of biological macromolecules and was also an important component of pollen wall cells; Os02g0611450 might regulate the synthesis and cell cycle of biological macromolecules. Comprehensively, rice grain length, grain width, grain thickness and fullness directly affected the grain weight of rice. By scanning electron microscopy, the filling rate investigation explained the difference in grain weight from the cell level and physiological level. Through QTL-seq combined with annotation gene transcriptional expression analysis and functional prediction, the candidate genes of grain weight could be screened more efficiently. Rice grain weight may be affected by protein phosphorylation and transcriptional regulation-related genes.

Key words: Rice, Grain weight gene, QTL-seq, Quantitative trait loci, SNP-index

CLC Number: 

• S511.4+2