Root traits for efficient nitrogen acquisition and genome-wide association study of root anatomical traits in maize (zea mays L.)

Open Access
- Author:
- Saengwilai, Patompong
- Graduate Program:
- Plant Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 11, 2013
- Committee Members:
- Jonathan Paul Lynch, Dissertation Advisor/Co-Advisor
Kathleen Marie Brown, Committee Chair/Co-Chair
Dawn S Luthe, Committee Member
Surinder Chopra, Special Member - Keywords:
- roots
anatomy
nitrogen
agriculture
aerenchyma
root hairs
crown roots
GWAS
QTL
SNP
genetics - Abstract:
- By 2050, the world population is predicted to reach 10 billion, almost double the current population. Feeding a growing population will become even more challenging. Since the advent of the Green Revolution in the 20th century, improved crop cultivars, chemical fertilizers, herbicides, and pesticides have been extensively used in order to increase agricultural productivity. As a result, agricultural food production was doubled within only four decades. Although several factors contributed to this doubling of world food production, a rapid increase in the use nitrogen (N) fertilizers seems to have played a major role. However, the continuous increase in the use of N fertilizers is causing detrimental impacts to the environment. For example, N fertilizers leached from agricultural areas to natural waters causes severe reductions in water quality by enhancing algal blooms, which disrupt normal functioning of ecosystems. Furthermore, nitrous oxide, which is a potent greenhouse gas, can be released to the atmosphere. Most importantly, the production of N fertilizer requires considerable energy from fossil fuels. As energy costs have risen in recent years, farmers face economic pressure from increasing N fertilizer costs. Therefore, relying on increasing N fertilization is not a sustainable solution for the future. We now need a “second green revolution” that will benefit resource-poor farmers by developing nitrogen efficient crop varieties that produce more food under low nitrogen conditions. A number of studies have shown that root traits play essential roles in N acquisition. Recently an ideotype of root traits for improved water and N acquisition has been proposed by Lynch (2013). Further research is needed to verify the physiological utility of these traits under low N conditions. Understanding the genetic control of root traits is also essential for plant breeders to develop breeding strategies that maximize genetic gain at reasonable time and costs. Root anatomical traits influence transport of water and nutrients, root mechanical strength, and interactions between roots and soil biota in rhizosphere. A number of experiments have shown significant benefits of root anatomical traits under biotic and abiotic stresses. Despite the high potential for improving crop performance and yield, few studies have been undertaken to characterize phenotypic variation and identify genetic control for root anatomical traits. My research is focused on the physiological utilities of maize root traits specifically 1) root cortical aerenchyma (RCA), 2) number of crown roots (CN) and 3) root hair length for enhanced nitrogen acquisition. The results suggest that these traits may be promising breeding targets for enhancing nitrogen acquisition from low N soils. Another topic is to study phenotypic variation and genetic control of 20 root anatomical traits of the Wisconsin diversity panel. Single nucleotide polymorphism markers (SNPs), associated with the traits, were identified using Genome-Wide Association Study (GWAS). Molecular markers associated with these traits may be useful in plant breeding programs using marker-assisted selection. The results of this study will greatly improve our understanding of the phenotypic variation and genetic control of root anatomical traits in maize (Zea mays L.).