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Title: Genetic and physical fine mapping of the novel brown midrib gene bm6 in maize to a 180 kb region on chromosome 2

item CHEN, YONSHENG - Iowa State University
item LIU, HONGJUN - Iowa State University
item ALI, FARHAD - Agricultural University Of Pakistan
item Scott, Marvin
item JI, QING - Iowa State University
item FREI, URSULA KAROLINE - Iowa State University
item LUBBERSTEDT, THOMAS - Iowa State University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2012
Publication Date: 10/1/2012
Citation: Chen, Y., Liu, H., Ali, F., Scott, M.P., Ji, Q., Frei, U., Lubberstedt, T. 2012. Genetic and physical fine mapping of the novel brown midrib gene bm6 in maize to a 180 kb region on chromosome 2. Theoretical and Applied Genetics. 125(6):1223-1235.

Interpretive Summary: Lignin is a compound in maize stalks that strengthens the stalk and protects the plant against insects. Lignin also influences the utility of maize biomass for biofuel production. We don’t fully understand what genes control the structure and content of lignin and this information would facilitate development of varieties with improved lignin content and/or structure. The gene bm6 is involved in lignin production but its role is not clear. We determined the precise location in the genome of the bm6 gene and scientists will use this information to understand its role in lignin biosynthesis, thus improving our ability to control lignin content and structure. This will ultimately allow us to develop maize varieties with better agronomic traits and utility for biofuel production.

Technical Abstract: Brown midrib mutants in maize are known to be associated with reduced lignin content and increased cell wall digestibility, which leads to better forage quality and higher efficiency of cellulosic biomass conversion into ethanol. Four well known brown midrib mutants, named bm1-4, were identified several decades ago. Additional recessive brown midrib mutants have been identified by allelism tests and designated as bm5, bm6, and bm7. In this study, we determined that bm6 increases cell wall digestibility and decreases plant height. Bm6 was assigned by quantitative bulked segregant analysis (BSA) onto the short arm of chromosome 2 and the map location was confirmed in a small segregating F2 population derived from crossing B73 and a bm6 mutant line. Subsequently, 960 brown midrib individuals were selected from the same but larger F2 population for fine mapping. With newly developed markers in the target region, the bm6 gene was assigned to a 180kb interval flanked by markers SSR_308337 and SSR_488638. In this region, 10 gene models are predicted in the maize B73 sequence. Analysis of these 10 genes as well as genes in the syntenic rice region revealed that four of them are promising candidate genes for bm6. Our study provided tightly linked markers for marker-assisted selection in relation to forage quality and lignocellulosic ethanol conversion of stover, will facilitate isolation of the underlying gene, and advance our understanding of brown midrib gene functions.