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Maize and Sunflower of North America: Conservation and Utilization of Genetic Diversity

Kost, Matthew
http://rave.ohiolink.edu/etdc/view?acc_num=osu1408642177

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Horticulture and Crop Science.
The genetic diversity in the crop landraces and crop wild relatives (CWRs) of the world is the `biological cornerstone’ of food security—we must ensure that it is conserved. Two important steps that could assist the in-situ conservation of this germplasm are: 1) determining how natural selection has shaped the distribution of functional genetic diversity across the landscape; and 2) identifying potential threats to this diversity. In addition, the former could assist landrace farmers in securing germplasm capable of withstanding future biotic and abiotic shifts by producing information on the locations of pertinent genetic diversity. In this body of work we provide examples of each of these steps—one from the maize landraces of Chiapas, Mexico (step 1) and the other from the sunflower system of the US (step 2). First, we sought understanding of how natural selection has shaped functional genetic diversity in Zea mays ssp. mays (maize) landraces grown along an elevational cline in Chiapas, Mexico by using RNA-seq approaches. We collected maize landraces from three elevational zones (highland, ~2100 m; midland, ~1550 m; and lowland, ~600 m) and planted them in a midland common garden. RNA-seq was performed on young leaf tissue. Weighted gene co-expression network analysis was used to identify co-expressed gene modules among landraces. Association analysis was then performed between landrace module expression values and environmental parameters of landrace origin. We identified an apparent tradeoff between an ABA dependent abiotic stress response in the lowland landraces and a possible plasma membrane repair/signaling response in the highland landraces. We then used the RNA-seq dataset to find signals of genetic differentiation in phenylpropanoid, flavonoid, and lignin biosynthesis between highland and lowland maize landraces. Genes differentially expressed between highland and lowland landraces were compared to a list of known and predicted genes involved in these pathways. Two salient patterns emerged. Highland landraces showed increased expression of genes involved in flavonol biosynthesis and a gene encoding the entry point into hydroxycinnamatic acid biosynthesis. Alternatively, lowland landraces showed increased expression of genes involved in anthocyanin and lignin biosynthesis. Second, we studied how the processes of natural selection influenced the introgression of crop-like traits into wild Helianthus annuus (sunflower) populations, which can lead to loss of genetic diversity in wild populations. Four crop-wild hybrid cross types, commonly found in sunflower hybrid zones, were grown together in a hybrid zone setting. We compared growth and life history traits and performed phenotypic selection analysis on early season traits to ascertain the likelihood, and potential routes, of crop allele introgression into wild sunflower populations. The four cross types all overwintered, emerged in the spring, and survived until flowering, indicating no early life history barriers to crop allele introgression. Direct selection for increased early season leaf size led to indirect selection on both increased early season plant height and earlier emergence. We identified variation in selection intensities given cross type, which has implications on likely routes of crop allele introgression. Combined, we provide examples of: 1) how functional genetic diversity is spread across the landscape; and 2) how crop toward wild introgression proceeds.
Kristin Mercer, Dr. (Advisor)
Erich Grotewold, Dr. (Committee Member)
Leah McHale, Dr. (Committee Member)
Andrew Michel, Dr. (Committee Member)
302 p.
Agriculture; Biology; Conservation; Ecology; Horticulture; Molecular Biology; Plant Biology; Plant Sciences; Sustainability
genetic diversity, WGCNA, maize, sunflower, local adaptation, RNA-seq, differential expression, crop-wild hybridization, gene flow, introgression, phenotypic selection, life history, Helianthus annuus, Zea mays, flavonoids, flavonol, anthocyanin, lignin

Recommended Citations

Citations

  • Kost, M. (2014). Maize and Sunflower of North America: Conservation and Utilization of Genetic Diversity [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408642177

    APA Style (7th edition)

  • Kost, Matthew. Maize and Sunflower of North America: Conservation and Utilization of Genetic Diversity. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1408642177.

    MLA Style (8th edition)

  • Kost, Matthew. "Maize and Sunflower of North America: Conservation and Utilization of Genetic Diversity." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408642177

    Chicago Manual of Style (17th edition)

osu1408642177
812
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This open access ETD is published by The Ohio State University and OhioLINK.