Functional implications and association mapping of root hydraulic traits for improved drought tolerance in maize (Zea mays L.)
Open Access
- Author:
- Klein, Stephanie
- Graduate Program:
- Plant Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 11, 2020
- Committee Members:
- Jonathan Paul Lynch, Dissertation Advisor/Co-Advisor
Jonathan Paul Lynch, Committee Chair/Co-Chair
Kathleen Marie Brown, Committee Member
Jesse R Lasky, Committee Member
Charles T Anderson, Outside Member
Teh-Hui Kao, Program Head/Chair - Keywords:
- Root
Metaxylem
Drought
Maize
High-throughput Phenotyping
Genome-wide Association Study - Abstract:
- Drought stress is a primary constraint on global maize (Zea mays) production and selection of root phenes may mitigate plant productivity losses in rainfed agricultural systems in regions most vulnerable to drought stress. Variation in root architecture and root anatomy has been associated with variable drought tolerance, but several questions remain regarding how interactions amongst individuals influence performance outcomes. Quantitative evaluation of maize root systems is difficult but has been made easier by technological advances that increase the capacity of our phenotyping efforts. The following work uses physiology experiments in the greenhouse and in the field and genetics analyses to understand how natural variation in root hydraulic phenes integrate to affect drought tolerance and to identify novel genetic loci associated with root metaxylem phenes. Chapter 1 contains a general introduction of drought stress, root hydraulics and other root traits. Chapter 2 presents numerous integrated phenotypes, or combinations of root architecture and anatomy phenes, that were associated with drought tolerance within a large maize diversity panel and carry direct implications for ideotype breeding. Many of these integrated phenotypes centered on different drought tolerance mechanisms including facilitating deeper root construction by cheapening tissue maintenance costs, optimizing hydraulic capacity, and improving penetration of hard, drying soils. Chapter 3 dissects further the physiological mechanisms underlying optimal root hydraulic capacities and found that the optimal root hydraulic architectures varies with increasing drought severity. In Chapter 4, numerous genetic loci associated with root metaxylem phenes under drought stress and non-stress were identified, including loci that co-localized in both water treatments and loci that were similarly significantly associated with root metaxylem phenes in rice. This research demonstrates that root metaxylem and the remaining hydraulic architecture merit further investigation as a breeding target for more drought tolerant maize.