| Plant height is an important agronomical trait related to plant architecture and yield potential in bread wheat.Reducing plant height appropriately can not only increase the lodging capacity for a stable production,but also can improve the harvest index,so it is an important targeting trait in wheat breeding.We previously identified a major quantitative trait locus(QTL)QPH.caas-6A flanked by simple sequence repeat markers Xbarc103 and Xwmc256 on chromosome 6AL,which could reduce plant height by 8.0–10.4%.In this study,QPH.caas-6A was confirmed using 256 recombinant inbred lines(RILs)derived from the Jingdong 8/Aikang 58 cross and narrowed down by a combination of SNP chip genotyping assays and genomic mining approaches.The efficacy of the newly developed markers was validated by testing 242 wheat varieties.The combining analysis of Rht24 with Rht1,Rht2 and Rht8 further indicated the distribution of Rht 24 and the predominant combination of wheat dwarfing genes.The main results are listed as follows:1.Confirmation of QPH.caas-6AQPH.caas-6A was previously mapped into an 8.2 cM interval flanked by Xbarc103 and Xwmc256.QPH.caas-6A was validated using 256 recombinant inbred lines(RILs)derived from the Jingdong 8/Aikang 58 cross with two SSR markers,designated as Rht24.2.Narrow-down of Rht24 by the genome mining approachXbarc103 and Xwmc256 were identified as the closest markers flanking Rht24.The target sequences of Xbarc103 and Xwmc256 were used as queries to BLAST against the International Wheat Genome Sequence Consortium database and hitted a super scaffold of approximately 208 Mb.Based on gene annotation of the scaffold,20 genes related to plant morphogenesis and hormone regulation were selected for developing gene-specific markers.Of them,only three gene-specific markers were polymorphic between the two partents,Jingdong 8 and Aikang 58.Then Rht24 was delimited to a 1.85 cM interval between TaAP2 and TaFAR.3.Enriching molecular markers in the Rht24 region by a combination of SNP genotyping assays and genomic identificationIn total,794 SNPs were identified from chromosome 6AL by SNP chip-based screening in combination with bulked segregant analysis.Based on the annotation information of SNP target sequences,ten SNPs were selected for developing molecular markers.Three of them were mapped within the region of Rht24.However,they did not further narrow down the target region of Rht24.4.Validation of molecular markers closely linked to Rht24Among 242 wheat varieties genotyped by markers TaFAR and TaAP2,Rht24 was present in 185(76.4%)varieties.Correlation analysis showed a significant association between Rht24 and plant height.Rht24 reduced plant height by an averaged 6.0–7.9 cm across environments and were significantly associated with an increased TGW of 2.0–3.4 g.5.Joint analysis of Rht1,Rht2,Rht8 and Rht24Rht24 was compared with the frequently used dwarfing genes,Rht1,Rht2 and Rht8 in the elite varieties of the Yellow and Huai Valley.The joint analysis indicated that Rht24 had the highest frequency distribution,and was frequently present in combination with Rht2 and Rht8. |
