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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #350787
Title: Selection signatures underlying dramatic male inflorescence transformation during modern hybrid maize breeding

Author
item GAGE, JOSEPH - University Of Wisconsin
item WHITE, MICHAEL - University Of Wisconsin
item Edwards, Jode
item KAEPPLER, SHAWN - University Of Wisconsin
item DE LEON, NATALIA - University Of Wisconsin

Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2018
Publication Date: 11/1/2018
Citation: Gage, J.L., White, M.R., Edwards, J.W., Kaeppler, S., de Leon, N. 2018. Selection signatures underlying dramatic male inflorescence transformation during modern hybrid maize breeding. Genetics. 210(3):1125-1138. https://doi.org/10.1534/genetics.118.301487.
DOI: https://doi.org/10.1534/genetics.118.301487

Interpretive Summary: Modern hybrid maize breeding has had many profound impacts on the morphology of the corn plant including leading to much reduced tassel size. The present study identifies the underlying genetic basis for the reduction in tassel size observed in modern corn hybrids. The physiological and genetic basis for the substantial reduction in tassel size remain unknown. Understanding the genetic basis will help us better understand why tassels have gotten small and will help breeders more efficiently manipulate this trait.

Technical Abstract: Inflorescence morphology plays a crucial role in reproductive fitness in plants. Maize is a monoecious species bearing separate male and female flowers (tassel and ear, respectively). The switch from open-pollinated populations of maize to hybrids in the early 20th century was accompanied by a reduction in tassel size, which has continued to decrease with hybrid breeding over the recent decades. The change to hybrid breeding methodology acted to reduce the fitness advantage conferred by having a prolific tassel. We sought to find genetic signatures that accompanied reduced overall tassel size. Using both a population of 942 diverse inbred maize accessions and a nested association mapping population comprised of three 200-line biparental populations, we measured 15 tassel morphological traits by manual and image-based methods. Genome-wide association studies identified 242 single nucleotide polymorphisms significantly associated with measured traits. We compared 41 inbreds developed from the Iowa Stiff Stalk Synthetic (BSSS) base population to 21 highly selected inbreds developed by modern commercial breeding programs and show that tassel size and weight were reduced significantly. We assayed genetic differences between the two groups using selection statistics XP-EHH, XP-CLR, and FST. All three selection statistics show evidence of selection at genomic regions associated with tassel morphology relative to genomewide null distributions. These results support the tremendous effect, both phenotypic and genotypic, that selection has had on maize male inflorescence morphology.