| Maize is one of the most important crops in China.Widely application of mechanized harvesting is of great significance to the enhancement of maize farming efficiency.However,major mechanized harvesting related traits belong to complex quantitative traits,determining by a number of genes.To dissect the genetic basis underlying these traits,an advanced segregation population is necessary.A population of CSSLs(chromosome segment substitution lines)has the advantage of eliminating the background noise for the study of complex quantitative trait loci.Two CSSLs populations were constructed by using the two elite inbred line as the recipient and donor parent,respectively.Inbred line HCL645 exhibited excellent mechanized harvesting traits,and elite inbred Zheng 58 was widely used.Finally,the CSSLs population was veritified by QTL analysis for ear-related traits.The main results are as follows:1.With HCL645 as the recipient,and Zheng 58 as the donor,a population(CSSLs Z58)of 115 homozygous CSSLs were obtained in BC4F2,BC5F2 and BC5F3 generations.The total length of the substitution segment was 7725.63 c M,with an average length of 67.18 c M.The total size of unique introgressed segments was 4026.33 c M,corresponding to a genome coverage of 52.22%.The background recovery rate of the substitution line was 98.13-99.73%.The chromosome coverage ranged from 23.07%,as of chromosome 9,to 80.74%,as of chromosome 5.2.With Zheng 58 as the recipient,and HCL645 as the donor,a population(CSSLs HCL645)of 116 CSSLs were obtained.Among which 65 were heterozygous CSSLs carry one segment.The total length of the substitution segment was 4184.31 c M,with an average length of 64.37 c M.The total length of unique introgressed segments was 3082.81 c M,covering 35.96% of the donor genome.The background recovery rate of the substitution line was 98.13-99.73%.The coverage of chromosome ranged from 3.14% as of chromosome 7,to 78.6% as of chromosome 5.3.99 homozygous SSSLs Z58 were used for QTL mapping,and 110 QTLs were detected,including cob hardness(CH),ear length(EL),ear diameter(ED),ear row number(ERN)and kenrel number of row(KNR).27 QTLs related to CH were distributed on the all chromosomes except for chromosome 9,of which 7 QTLs were detected simultaneously in two environments.The contribution of these QTLs was 6.71-27.64%.30 QTLs related to EL were located on all chromosomes except chromosome 9,5 QTLs of which were detected in both two environments.The contribution of these QTLs was 2.31-26.76%.17 QTLs related to ED were distributed on chromosome 2,3,4,5,7,8,2 QTLs of which were detected in two environments simultaneously,with a contribution of 4.87-18.66%.18 QTLs related to ERN were distributed on all chromosomes except for chromosome 9 &10,1 QTL of which in two environments,with a contribution of 1.31-10.2%.19 QTLs related to KNR were distributed on the all but chromosome 1,3 QTLs of which in both environments,with a contribution of 3.71-15.28%.41 QTLs were found to be associated with three or more traits.Two QTLs located at umc2255-umc2049-umc2377-umc1886-bnlg1325(bin3.01-3.02)and bnlg2181-umc2356-umc1960-umc1724(bin8.06)were associated with five traits,indicating the existance of pleiotropic gene clusters on these loci.The bi-directional CSSLs developed in this study provided a foundation for the study of the genetic basis of mechanized harvesting related traits in maize. |
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