Fine Mapping Of A Quantitative Trait Locus QKL9 For Kernel Length In Maize(Zea Mays L.)

Maize kernel size, including kernel length, kernel width and kernel thickness, are rather complex traits controlled by a good many minor genes, and become vitally important indicators for genetic improvement of grain yeild. In a previous study, an F2 population was constructed as initial mapping population, derived from two elite maize inbred lines, Mc with small kernel size, while V671 with large kernel size. QTL mapping was implemented to investigate the molecular and genetic basis of kernel size. Based on previous results, in this study, a major QTL on chromosome 9 with large effects controlling kernel length has been targeted for fine mapping and map-based cloning. The main results are as follows:1. A genetic map was constructed using 14 SSR markers spanned 22.9c M in length across target QTL, the average interval between adjacent markers was 1.76 c M. The order of SSR markers in the molecular linkage map was in line with the B73 reference genome.2. In BC2F2 population, the extent of recovery ranged from 76.19% to 95.83% revealed by background analysis, and the average rate was 89.04%. Plants harboring q KL9, with high recovery were chosen to fine mapping.3. ICIM method was employed for re-mapping kernel length QTLs in BC2F2 population and BC3F1 population respectively, and only one QTL q KL9 on chromosome 9 was identified in single-environment analysis, which was narrowed down between the flanking marker C9-123 and K57, and the QTL can account for 16.24% of phenotypic variation.4. To further narrow the target region harboring q KL9 down, a series of CSSLs were also developed by screening recombinant plants from an advanced backcross population. Progeny test was employed, and finally the target QTL(q KL9) was narrowed to 3Mb interval between markers C9-123 and C9-129.