| Maize is one of staple grain crops in China,but the drought and nutrient stress seriously restrict maize productivity.The distribution of root system in deep soil could increase the absorption of water and nitrogen in maize,the crown root angle(CRA),number(CRN),diameter(CRD)are the key traits that determine the deep root of maize.While there are few genetic studies on the crown root of maize and the molecular genetic mechanism of CRA is not clear.In present study,root traits in maize seedling stage under drought stress were identified based on recombinant inbred line population which consist of 204 RILs derived from the cross between DH1M and T877,and QTL analysis was carried out with high density genetic map.Crown root angle,number,diameter of maize in field were identified based on RIL populationand BC2F5 population constructed from backcross between Teosinte X26-4 and Mo 17 in Hainan and Yizheng.The QTL mapping were conduted by composite interval mapping with a high density genetic map.The results were as follows:(1)Our results found that root traits(crown root angle,crown root number,crown root diameter,crown root length,primary root length,seminal root length,seminal root number)and(shoot traits which contain plant hight,leaf length,leaf width,shoot fresh weight,shoot dry weight)were extensively segregated and normally distributed,and considerable phenotypic variation existed in RIL population under normal and drought conditions at the seedling stage.Moreover,environment and treatment had significant effect on all traits measured in this study.Correlation between 6 shoot traits and 7 root traits indicated statistical significant existed in these characteristics under two moisture conditions,except SPAD,crown root angle and seminal root number.Totally 90 QTLs were detected from all traits measured in this study,which were distributed on 10 chromosomes of maize.Specifically,39 QTLs were detected from shoot traits including 23 QTLs underwell-watered conditions and 16 QTLs under drought stress,which explained 5.96-14.28%of the phenotypic variation.Additionally,51 QTLs were detected from root traits including 31 QTLs under well-watered conditions and 20 QTLs under drought stress,which explained 4.82-17.14%of the phenotypic variation.(2)In the field,1.9-2.8 fold phenotypic variations were found in RIL population(DH1M×T877)in two environment.Continuous distributions of phenotypes displayed transgressive segregation,which indicated that crown root angle,number and diameter were typical quantitative trait.Totally 21 QTLs for crown root angle,number and diameter were detected in Hainan and Yizheng,which were distributed on chromosomes 1,2,3,7,8,10,respectively,and explained 4.82-17.14%of the phenotypic variation and the LOD values was range from 2.53 to 4.91.We detected a QTL related to crown root angle and crown root diameter at 60.0 1cM on 3 chromsome,and detects a QTL qRA-7 which control the crown root angle at 210.11cM on 7 chromosome were detected at two places.Where qRA-1 is located at 193.7 cM on chromosome 1,the LOD value is 4.91,which can explain the phenotypic variation of 8.2%and this QTL were verified in associated population.Crown roots showed 2.1-2.5 fold phenotypic variations in BC2F5 population(teosinte X26-4×Mo17),and all traits showed continuous distribution.A total of 12 QTLs were identified in BC2F5 population,and the contribution to phenotypic variations for a single QTL ranged from 4.10%to 19.67%.QTL-qRA-4 associated with crown root angle was detected in 79.61cM of chromosome 4,which explained phenotypic variation up to 19.67%,and LOD value was 10.44.The results of this study can provide a fundamental basis for fine mapping and clone of QTLs related to crown root angle. |
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