Title: "High-density linkage mapping of tocochromanol variation in two biparental maize populations"
Speaker: Megan Fenton; Department of Agronomy, Purdue University

Place: Materials and Electrical Engineering (MSEE) B012
Date: April 21, 2015; Tuesday
Time: 4:30pm

Vitamin E refers to eight distinct compounds that are collectively and commonly known as tocochromanols. The tocochromanols are divided into two classes, tocotrienols and tocopherols. Tocochromanols are the major lipid-soluble antioxidants in maize (Zea mays L.) grain. Enhancing the vitamin E content of maize derived foods through plant breeding has important nutritional and health implications. Variation for tocochromanol content was previously assessed in the maize association panel, which includes the maize nested association mapping (NAM) population founders. Four inbred lines exhibiting unique variation for tocochromanol compounds were chosen from the maize association panel, as the NAM founders did not exhibit sufficient variation for the tocochromanol compounds of interest. Two biparental mapping populations (N6xNC296 and E2558xCo125) were developed to further dissect the genetic architecture of tocochromanol variation in maize grain. The populations were genotyped using genotyping-by-sequencing (GBS) and high-density linkage maps were constructed and each map contains over 1,200 single nucleotide polymorphism (SNP) markers. The tocopherol and tocotrienol variation in two replicates of each population was quantified using high performance liquid chromatography (HPLC). The N6xNC296 population exhibits variation for alpha-tocopherol and alpha-tocotrienol. The E2558WxCo125 population exhibits variation in the ratio of total tocotrienols to tocopherols. The tocochromanol content data revealed that there was transgressive segregation in the population progeny of both populations. Using composite interval mapping a novel QTL was identified for tocopherol ratio traits that contained homogentisate phytyl transferase (ZmVTE2) within the support interval. This locus was not identified in a genome wide association study that analyzed the maize association panel, which included the population parents used in this study. Overall, this work illustrates the complementary nature of biparental mapping populations to genome wide association studies in order to further characterize genetic architecture.

Associated reading:
Gibson, G. (2012). Rare and common variants: twenty arguments. Nature Reviews. Genetics. 13(2):135-45.

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