Development and high-throughput genotyping of substitution lines carting the chromosome segments of indica 9311 in the background of japonica Nipponbare

Chromosome segment substitution lines（CSSLs） are useful for the precise mapping of quantitative trait loci（QTLs） and dissection of the genetic basis of complex traits.In this study,two whole-genome sequenced rice cultivars,the japonica Nipponbare and indica 9311 were used as recipient and donor,respectively.A population with 57 CSSLs was developed after crossing and back-crossing assisted by molecular markers, and genotypes were identified using a high-throughput resequencing strategy.Detailed graphical genotypes of 38 lines were constructed based on resequencing data.These CSSLs had a total of 95 substituted segments derived from indica 9311,with an average of about 2.5 segments per CSSL and eight segments per chromosome,and covered about 87.4%of the rice whole genome.A multiple linear regression QTL analysis mapped four QTLs for 1000-grain weight.The largest-effect QTL was located in a region on chromosome 5 that contained a cloned major QTL GW5/qSW5 for grain size in rice.These CSSLs with a background of Nipponbare may provide powerful tools for future whole-genome

Clustered spikelets 4,encoding a putative cytochrome P450 protein CYP724B1,is essential for rice panicle development

Rice(Oryza sativa L.)inflorescence(panicle)architecture is an important agronomic trait,serving as one of the determinants of rice yield.A number of genes related to panicle development have been cloned and functionally characterized so far.However,more information is needed for fully understanding of the mechanism underlying the panicle development.In the present study,we identified a clustered spikelets 4(cl4)mutant in the 93-11 genetic background.Compared to its wild-type 93-11,cl4 mutant has a typical clustered spikelets phenotype with all primary branches clustered on the base of the main rachis and 2–3abnormal spikelets clustered on the primary branches.Moreover,cl4 mutant also shows shorter plant height than that of the wild type.Map-based cloning strategy is performed to clone the CL4 gene.As a result,CL4 is demonstrated to encode a putative cytochrome P450 protein CYP724B1,which is involved in brassinosteroid biosynthesis.To confirm our mapping result,the CL4 RNAi transgenic plants are generated.And the transgenic plants also show similar phenotype as the cl4 mutant.These results provide strong evidence that CL4 plays an important role in rice panicle development as well as plant height regulation.