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Title:Agronomic and marker-assisted breeding strategies for improving nitrogen use efficiency in maize
Author(s):Terras Mastrodomenico, Adriano
Director of Research:Below, Frederick
Doctoral Committee Chair(s):Below, Frederick
Doctoral Committee Member(s):Bohn, Martin; Brown, Patrick; Lipka, Alexander
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Nitrogen use efficiency
Expired plant variety protection germplasm
Genomic selection
Abstract:Nitrogen (N) is an essential mineral nutrient required for maize (Zea mays L.) development. Increased maize yields will be necessary as the world demand for food increases. However, with the growing concern for food security, maize yield increases must be obtained using more sustainable agricultural practices with less N fertilizer inputs. Improved nitrogen use efficiency (NUE) can maximize maize yield with minimal inputs of N fertilizer, but requires coordinated progress in several areas of the crop’s production (e.g. genetic improvement, genetic characterization, and crop management). The objectives of this PhD research were i) evaluate the genetic variation of N-use traits and their interaction with the environment, ii) identify the genomic prediction accuracy of different N-use traits and their application in maize NUE breeding programs, iii) understand the relative merits of important agronomic factors (e.g. N stress tolerance, yield response to N fertilizer, crowding stress tolerance, and yield response to narrower row spacing) to maize yield, and iv) evaluate the importance of hybrid characterization for agronomic traits to obtain maximum maize yield potential. The research objectives were addressed using a large set of maize hybrids derived from expired plant variety protection- certified (named ex-PVP) and commercial germplasms and evaluating them in state-wide field experiments for different agronomic traits. In addition, all ex-PVP inbred lines were genotyped with 26,769 single-nucleotide polymorphism. Field experiments evaluated the NUE performance of 522 maize hybrids derived from the genotyped ex-PVP inbreds. Genomic prediction accuracy for yield ranged from 0.17 to 0.53 and 0.17 to 0.72 under low and high N conditions (0 and 252 kg N ha-1), respectively. The two major agronomic factors influencing a hybrid’s NUE performance are the tolerance to N stress (yield under unfertilized N conditions) and the yield response to additional N fertilizer (yield change between unfertilized and N fertilized plots). However, yield under N stress conditions and yield response to N fertilizer are negatively correlated traits. As a result, less than 10% of all hybrids evaluated in this study combined above average performance for N stress tolerance and yield response to N fertilizer. Harvest index under low N was the secondary trait that was highly correlated (+0.63, P ≤ 0.001) to yield under low N and provided the highest genomic prediction accuracy (ranged from 0.26 to 0.78) under low N conditions. Similarly, the yield response to N fertilizer (e.g. NUE) was highly correlated (+0.74, P ≤ 0.001) to yield under high N and provided the highest genomic prediction accuracy (ranged from 0.05 to 0.51) under high N conditions. These traits could be integrated into maize breeding programs targeting for improved hybrid performance under N stress and high N conditions, respectively. Maize yield stability and performance were influenced by N fertilizer and plant density conditions. Hybrids with above average yield performance under low N environments exhibited high yield stability under high N environments. On the other hand, hybrids with an above average yield response to N fertilizer and increased plant density exhibited greater yield in high N environments. Commercial hybrids showed a large variation in their yield response to different crop management conditions. In addition the level of N stress tolerance and the yield response to N fertilizer, the yield response to narrower row spacing was another important agronomic factor influencing maize yield. Maize genotypes grown under high N conditions, high plant density, and narrow row spacing (312 kg N ha-1, 108,000 plant ha-1, at 50 cm row spacing) combined high broad-sense heritability and yield performance. Therefore, breeding programs evaluating maize genotypes under intensive agronomic management conditions can obtain greater genetic gain. Future maize yield increases will rely on genotypes that combine improved yield response to N fertilizer and tolerance to high plant densities at narrower row spacing conditions. Accordingly, the characterization of maize hybrid’s responses to different agronomic factors gives farmers the knowledge to better match their hybrids with the recommended management to obtain the hybrid’s maximum yield potential.
Issue Date:2017-04-11
Type:Thesis
URI:http://hdl.handle.net/2142/97305
Rights Information:Copyright 2016 Adriano Terras Mastrodomenico
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05


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