DISSECTING COMPLEX TRAITS IN MAIZE AND BIOFUEL GRASSES BY APPLYING GENOMICS, BIOINFORMATICS, AND GENETIC RESOURCES
Location: Plant, Soil and Nutrition Research
Title: Genome-wide association study of maize identifies genes affecting leaf architecture
Submitted to: Nature Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2010
Publication Date: January 9, 2011
Citation: Tian, F., Bradbury, P., Brown, P., Sun, Q., Flint Garcia, S.A., Rocheford, T.R., McMullen, M.D., Holland, J.B., Buckler IV, E.S. 2011. Genome-wide association study of maize identifies genes affecting leaf architecture. Nature Genetics. 43:159-162.
Interpretive Summary: U.S. maize yield has increased eightfold in the past 80 years with half of the improvement attributed to genetics. Contributing to those higher yields, changes in maize leaf angle and size have provided a basis for more efficient light capture as plant densities increased. In addition, two different mutations, called liguleless-1 and liguleless-2 have been shown to eliminate the collar or ligule separating the leaf blade from the sheath and to make maize leaves more upright. Although these mutations were shown to increase yield in certain backgrounds, they have never been used in commercial hybrids. This research showed that less severe, previously unrecognized mutations at these loci have contributed significantly to leaf angle changes and to adaptation to modern planting practices and provided evidence that additional genes have been involved as well. These conclusions were based on research that used the maize nested association mapping population (NAM) to map genes associated with leaf traits. The NAM population consists of about 5000 inbred lines developed from 25 different crosses. The design allowed scientists to eliminate population structure effects in their analysis and to make use of 1.6 million genetic markers that had been scored on the NAM parents. The combination of the large NAM population and large number of genetic markers made it possible to locate genetic effects very accurately.
U.S. maize yield has increased eightfold in the past 80 years with half of the improvement attributed to genetics. Changes in maize leaf angle and size provided a basis for more efficient light capture as plant densities increased. Through a genome wide association study (GWAS) of the maize nested association mapping (NAM) panel, we determined the genetic basis of important leaf architecture traits and identified some of the key genes. Overall, we demonstrated that the genetic architectures of the leaf traits are dominated by small effects, with little epistasis, environmental interaction or pleiotropy. In particular, GWAS results show that variations at the liguleless genes have contributed to more upright leaves. These results demonstrate that the use of GWAS with specially designed mapping populations is a powerful approach to uncover the basis of key agronomic traits.