| Maize is the crop with the largest planting area in China.However,most of them are distributed in arid and semi-arid regions.At present,some methods such as deep-sowing can be used to resist drought in maize production.But the existing maize varieties have poor deep-sowing germination ability,resulting in a decrease in the emergence rate and even affects maize yield.Therefore,it is necessary to accelerate the breeding of new maize varieties with strong deep-sowing germination ability.However,the genes related to deep-sowing germination ability of maize have not been identified and utilized,which results in a slow breeding process.QTL mapping of deep-sowing germination traits in maize can lay a theoretical foundation for further fine mapping and map-based cloning,and also provide germplasm resources and molecular marker for maize breeding.In this study,243 IBM Syn4 RIL lines were used as mapping population which was built by maize inbred line B73 with strong deep-sowing germination ability and Mo17 with poor deep-sowing germination ability.The results of QTL analysis for deep-sowing germination traits were showed as follows:1.The results of phenotypic identification showed a single peak curve occurred at the frequency distribution of emergence rate,seedling length,plumule length,mesocotyl length,coleoptile length of IBM syn4 RIL population at 12.5 cm sowing depth,which basically conformed to normal distribution.The above results suggest that deep-sowing tolerance is a quantitative trait controlled by polygenes.The maximum value of these traits was 93.3%,16.3 cm,7.9 cm,11.4 cm or 4.4 cm respectively,which was increased by 6.6%,0.3 cm,0.8 cm,2.4 cm and 0.6 cm compared with B73,the deep-sowing tolerant parent line.These deep-sowing tolerant lines of IBM Syn4 RIL population can be used as germplasms for maize breeding.2.1339 polymorphic SSR markers covering the whole genome were used to construct molecular marker linkage genetic map.The composite interval mapping based on the mixed linear model was applied to perform QTL mapping.Totally,there were 31 QTLs controlling deep-sowing germination traits.Seven QTLs of emergence rate were detected and they explained 3.52%?10.49% of the phenotypic variance with LOD scores ranging from 3.04 to 8.27.In addition,7,5,10,2 QTLs for seedling length,plumule length,mesocotyl length,coleoptile length were detected and they explained 3.56%?9.82%,3.78%?5.96%,2.75%?5.82%,3.83%?8.66% of the phenotypic variance with LOD scores ranging 2.68?8.02,2.78?3.92,2.50?4.64,2.78?4.10,respectively.3.Further analysis showed that there were 5 overlapping regions among QTL segments of different deep-sowing germination traits.The overlapping regions were located at the interval of 566.01?580.01 c M on Chromosome 3,204.01?210.31 c M on Chromosome 5,233.61?246.21 c M on Chromosome 7,351.01?361.71 c M and 469.01?479.01 c M on Chromosome 9.In total,298 candidate genes were mined in these five overlapping intrevals.Twelve of them were key candidate genes of GA,ABA,IAA and MYB signaling pathways.It was speculated that deep-sowing germination of maize seeds might be regulated by hormones and MYB proteins. |
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