Development Of Chromosome Segment Substitution Line And Positioning Analysis Of A Major Tassel Branch Number QTL QTBN7-1 In Maize

Chromosome Segment Substitution Lines?CSSLs?is an ideal line for fine mapping and gene cloning of QTL.It is a secondary mapping population constructed by backcross and self crossing selection of the whole genome donor fragment.In this study,a set of chromosomal fragment introgression populations containing 180 materials was constructed using Ye478and Qi319,and QTLs for 10 traits were performed on this population..The main results of this study are as follows:?1?This experiment used Ye478 as the recurrent parent and Qi319 as the donor parent,using 132 polymorphism analysis markers screened in the common primers of the MaizeGDB database,and 68 markers designed based on the genomic resequencing information of Ye 478and Qi319 for molecular marker-assisted selection of CSSLs.Through continuous multiple generations backcross and self crossing,180 chromosome fragments were introduced into the line,covering 200 molecular markers on 10 chromosomes of maize,and the background recovery rate was over 98%.?2?The chromosomal segment introgression lines were identified for two-and four-point in field phenotypic characters and panicle traits after harvest in Changping and Shunyi,Beijing in 2016 and 2017,using T-tests to detect whether there were significant differences in the traits between CSSLs and Ye478.The results showed that a total of 72 QTLs were detected in 5 maize agronomic traits,of which 13 QTLs were detected in plant height,24QTLs were detected in ear height,13 QTLs were detected in tassel length,18 were detected in tassel branch number and 4 QTLs were detected in internode number;and a total of 43 QTLs were detected in 5 maize ear traits,of which 11 QTLs were detected in ear length,6 QTLs were detected in ear diameter,6 QTLs were detected in ear row number,10 QTLs were detected in grain length,10 QTLs were dectected in grain width.?3?Based on QTL analysis of chromosome segment introgression lines,there was a significant difference between chromosome segment introgression line CL103 and Ye478 in bin7.02 region,using CL103 for the positioning of maize tassel branch number.The results showed that in Changping 2017,the difference of tassel branch number of two parents reached a very significant level,the average number of parent CL103 was 24.3,the parent Ye478 was18.2 and the F₂ population was 22.03.A major QTL for tassel branch number was located in the 110,088,645-110,160,101 bp region of chromosome 7 by using the complete interval mapping method,the LOD value was 25.06,which explained 11.47%of the phenotype,and the additive effect was 1.74,This interval contains 14 Candidate genes,including the reported gene ramosa1?ra1?.Previous studies have shown that the candidate gene ra1 encodes Arabidopsis homologous cis-trans isomerase family protein,which has a higher expression level in maize tassels and can significantly increase the tassel branch number.