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Description

Title:High-throughput phenotyping and genetic mapping of photosynthetic traits and ozone responses in maize and soybean
Author(s):Montes, Christopher M
Director of Research:Ainsworth, Elizabeth A
Doctoral Committee Chair(s):Ainsworth, Elizabeth A
Doctoral Committee Member(s):Bernacchi, Carl J; Diers, Brian W; Ort, Donald R
Department / Program:Plant Biology
Discipline:Plant Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):ozone
soybean
maize
high-throughput modeling
Abstract:Global population growth is placing additional demand on current agronomic production with global climate change expected to limit future increases in yields. Tropospheric ozone (O3) is a secondary pollutant that is toxic to plants, negatively affects productivity and ultimately reduces crop yield. With current tropospheric O3 concentrations already causing sizeable damage and predicted increases in O3 concentrations leading to greater yield reductions, better understanding of the genetic underpinnings of O3 sensitivity in major crops is essential to alleviate the damage caused by O3. Pursuing novel traits like improved photosynthesis is also proposed as a means of attaining the necessary increases in crop yields to meet the demands of a growing world population. This thesis uses a forward genetics approach to map O3 responses of soybean and maize, and develops a high-throughput method to map photosynthetic leaf-level traits in soybean. Most studies of plant responses to elevated O3 have occurred in C3 plant species. The goal of Chapter 2 was to improve understanding of the O3 response in maize. B73 and Mo17, two of the advanced public lines representing the Stiff Stalk and Non-Stiff Stalk heterotic groups, were grown under elevated and ambient O3 concentrations in the field. A number of traits including photosynthesis, development, and yield were significantly decreased by elevated O3. The degree to which O3 negatively affected these traits varied between the two inbred lines indicating different sensitivity to elevated O3. Additionally, the severity of the O3 response varied within years of the experiment suggesting the detrimental effects of O3 to maize are dependent on other environmental conditions. Two near-isogenic line populations with B73 and Mo17 as the recurrent parents were also grown under ambient and elevated O3 concentrations to map O3-related traits. Previously unidentified quantitative trait loci (QTL) for photosynthetic traits in maize as well as QTL related to O3 tolerance were identified. The goal of the research in Chapter 3 was to identity QTL within the soybean genome that are associated with intraspecific variation in response to O3. Two soybean varieties that had shown different sensitivity to elevated O3 were used to develop a recombinant inbred line population. This RIL population was grown in the field to maturity under ambient and elevated O3 concentrations to map O3 related agronomic traits. O3 negatively affected most measured traits across all three years of the experiment. Numerous stable and environment-specific QTL for important agronomic traits in soybean were identified. Many of the QTL for different traits were co-located suggesting pleiotropy or closely linked QTL. Strong QTL by environment interactions were identified in this experiment with the direction of the effect of many QTLs varying between growing seasons. Phenotyping many plants for the rate limiting steps of photosynthesis is prohibitively time-consuming and has received little attention in breeding programs for this reason. Chapter 4 attempted to address this issue by further developing a high-throughput technique using a partial least squares regression modelling approach and rapidly collected hyperspectral leaf reflectance data to estimate the maximum rate of carboxylation by Rubisco (Vc,max) and the maximum rate of RuBP regeneration (Jmax) as well as other leaf biochemical and structural traits. The applicability of this approach was demonstrated by performing a genome-wide association study on the entirety of the Soybean Nested Association Mapping panel over two growing seasons. Significant marker trait associations were identified for both rate limiting steps of photosynthesis (normalized to 25°C), specific leaf area, leaf carbon and nitrogen percentage on a mass basis, and chlorophyll content. The research presented in this dissertation helps identify traits that can be monitored to identify O3 tolerant varieties and provides a first step in discovering the underlying genetic controls of the intraspecific response of maize and soybean to elevated O3. This research advances our understanding of how both crops respond to O3 pollution, identifies potential targets for future breeding programs, and promotes the use of FACE technology as a viable method that can be used for phenotyping large plant populations and mapping O3 tolerance. The high-throughput nature of the technique presented in Chapter 4 and relative ease in data collection makes it a promising method to incorporate improved photosynthetic traits into a breeding program or allow for large surveys of soybean germplasm for these traits. In total, this dissertation provides tangible information and tools to improve maize and soybean production in current and future atmospheres.
Issue Date:2020-05-04
Type:Thesis
URI:http://hdl.handle.net/2142/107963
Rights Information:Copyright 2020 Christopher Montes
Date Available in IDEALS:2020-08-26
Date Deposited:2020-05


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