CUR - The Council on Undergraduate Research

Analysis of Plant Height in Zea mays

Chase Krug, Dr. Matthew Hufford, Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 3410 Beardshear Hall, Ames, IA 50011

The genetic diversity between two parental lines of maize can influence heterosis. Heterosis is the process in which traits in the offspring surpass those of parents. However, correlation between heterosis and the cross direction (i.e., which line is used as male and which as female) and genetic distance remains unknown. All possible combinations of four maize groups (flint, tropical, stiff-stalk and non-stiff stalk), spanning a range of genetic distance were crossed to one another, resulting in 16 distinct cross types. We directly tested the effect of maternal and paternal background and genetic distance on heterosis using a diallel experiment, which is a mating scheme in which lines are crossed in all possible directions. The diallel consisted of 158 crosses which were replicated in three blocks. Mid-parent and high-parent heterosis were calculated using both plant height and ear height data. Mid-parent heterosis is when plant height of the cross is greater than the average height of both parents. High parent heterosis is when height of the cross is greater than that of the best performing parent. Heterosis was compared using statistical contrasts which test the significance of the direction of the cross and different combinations of heterotic groups. Our results indicate significant mid-parent/high-parent heterosis across all heterotic groups. Additionally, specific reciprocal crosses show a significant difference in mid-parent/high-parent heterosis. Statistical analyses were conducted, and plots were created in the R programming language. Our increased understanding of the phenomenon of heterosis will facilitate prediction of its occurrence in, for example, cultivar improvement.

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