Development Of Chromosome Segment Substitution Line With YS501 As Recipient And QTL Mapping For Leaf Angle

Maize is an important food and feed crop in the world.Maize leaf angl is an important index of plant type,and directly affects the photosynthesis of the leaves,thus affecting the yield.Analyzing the genetic mechanism of leaf angles and clonning related gene provide a theoretical basis for maize ideal plant type breeding.Chromosome segment substitution lines have the advantage of eliminating the interference of genetic background and are ideal materials for QTL mapping.In this study,the maize inbred line LDC-1 was used as the donor parent,and the YS501 was used as the recipient parent.Based on molecular marker-assisted selection,a chromosome segment substitution line population was constructed.On this basis,the QTL related to the leaf angle in two field-grown environments were identified.In addition,a recombinant inbred line population derived from YS501 and LDC-1 was used to map QTLs for leaf angle in three field-grown environments.The main findings are as follows:1.711 pairs of SSRs covering the whole maize genome were used to detect YS501 and LDC-1,it was found that 125 pairs of SSR markers had polymorphisms among parents,and the frequency of polymorphism was 17.6%.In order to gradually reduce the number of donor chromosome fragments in the individual back crossed offspring,molecular marker-assisted selection using the above-mentioned polymorphic molecular markers was carried out for the backcrossed progeny with LDC-1 as the donor parent and YS501 as the recipient parent.As a result,153 chromosome fragments substitution lines were constructed after 5 backcrossings and 2 selfings.2.A 10K gene chip was used to genotype the above 153 chromosome segment substitution lines.It was found that these chromosome segment substitution lines carried a total of 1326 donor segments,and each substitution line carried 8.33 donor segments on average.Each chromosome carries 132.6 substitution fragments on average,and the average length of substitution fragments is 13.164 Mb.The total length covered by the substitution fragments is 16502.68 Mb,which is 7.8 times of the entire maize B73 reference genome.3.By using 153 chromosome segment substitution lines as materials,the QTLs for leaf angle above ear were mapped in 2 field planting environments.A total of 14 QTLs were detected on chromosomes 1,2,3,4,6,7 and 10.The LOD value ranges from 3.13 to 12.54,and the phenotypic variation explained by a single QTL ranges from 3.53%to 15.55%.qLA1-3 on chromosome 1 was repeatedly detected in two environments,and it is a major QTL that controls the angle of leaves above ear.The highest LOD value is 7.6,and the highest phenotypic variation explained is 15.55%.The remaining 13 QTLs were only detected in a single environment.4.By using 186 recombinant inbred lines derived from YS501 and LDC-land the genetic map of the lines,QTLs for leaf angle above ear were mapped in 3 field planting environments.A total of 13 QTLs were detected on chromosomes 1,2,3,4,5,6,7 and 10.The LOD value ranges from 2.7 to 7.21,and the phenotypic variation explained by a single QTL ranges from 3.93%to 12.64%.The QTL qLA2-3 on chromosome 2 was detected in 3 environments,and it is the main QTL that controls the leaf angle above ear.The highest LOD value is 7.03,and the highest phenotypic variation explained is 12.31%.The remaining 12 QTLs were only detected in a single environment scattered individually on maize chromosome.5.Comparing the QTL mapping results of leaf angle in the chromosome segment substitution line population and those of the recombinant inbred line population,it was found that the QTL on chromosome 6 was detected in both populations.Previous studies have also reported this leaf angle QTL,but no related genes have been cloned.The above results lay the foundation for further fine mapping gene for leaf angle.