Abstract
Leaf width (LW) influences canopy architecture of population-cultured maize and can thus contribute to density breeding. In previous studies, almost all maize LW-related mutants have extreme effect on leaf development or accompanied unfavorable phenotypes. In addition, the identification of quantitative trait loci (QTLs) has been resolution-limited, with cloning and fine-mapping rarely performed. Here, we constructed a bin map for 670 recombinant inbred lines (RILs) using ∼1.2 billion 100-bp re-sequencing reads. QTL analysis of the LW trait directly narrowed the major effect QTL, qLW4, to a ∼270-kb interval. A fine-mapping population and near-isogenic lines (NILs) were quickly constructed using a key RIL harboring heterozygous genotypes across the qLW4 region. A recombinant-derived progeny testing strategy was subsequently used to further fine-map qLW4 to a 55-kb interval. Examination of NILs revealed that qLW4 has a completely dominant effect on LW, with no additional effect on leaf length. Candidate gene analysis suggested that this locus may be a novel LW controlling allele in maize. Our findings demonstrate the advantage of large-population high-density bin mapping, and suggest a strategy for efficiently fine-mapping or even cloning of QTLs. These results should also be helpful for further dissection of the genetic mechanism of LW variation, and benefit maize density breeding.
Highlights
Leaf is the most important organ for photosynthesis, which is the process of providing most carbohydrates for plant growth and development
Accelerated Quantitative trait locus (QTL) Fine-Mapping by Re-sequencing of Large recombinant inbred lines (RILs) in Maize
Bin mapping, which is based on bar-coded multiplexed resequencing, can increase linkage map resolution, thereby improving QTL mapping accuracy and saving time and resource (Huang et al, 2009)
Summary
Leaf is the most important organ for photosynthesis, which is the process of providing most carbohydrates for plant growth and development. The width of leaves influences canopy architecture in population-cultured maize and affects photosynthetically active radiation and light signal transmission (Vogelmann and Gorton, 2014). Excessively narrow leaves are benefit for light transparency, but greatly. Fine-Mapping Maize Leaf Width QTL limit light capture (Pepper et al, 1977). The excessively wide one vastly reduce light transmitted to middle and lower leaves, thereby reduce the overall photosynthetically active radiation and cause shading avoidance, a syndrome results in lots of disadvantageous phenotype for maize development (Kebrom and Brutnell, 2007). The trade-off between LW and light capture or signal transmission is important for maize breeding, and an efficient tool is needed to manipulate LW without causing negative impacts. The identification of alleles controlling LW would be beneficial for understanding mechanisms of leaf development; it would be helpful for the intentional modification of leaf architecture and assist maize breeding, especially density breeding
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