Genetic Dissection of Grain Yield and Agronomic Traits in Maize under Optimum and Low-Nitrogen Stressed Environments

Abstract

Understanding the genetic basis of maize grain yield and other traits under low-nitrogen (N) stressed environments could improve selection efficiency. In this study, five doubled haploid (DH) populations were evaluated under optimum and N-stressed conditions, during the main rainy season and off-season in Kenya and Rwanda, from 2014 to 2015. Identifying the genomic regions associated with grain yield (GY), anthesis date (AD), anthesis-silking interval (ASI), plant height (PH), ear height (EH), ear position (EPO), and leaf senescence (SEN) under optimum and N-stressed environments could facilitate the use of marker-assisted selection to develop N-use-efficient maize varieties. DH lines were genotyped with genotyping by sequencing. A total of 13, 43, 13, 25, 30, 21, and 10 QTL were identified for GY, AD ASI, PH, EH, EPO, and SEN, respectively. For GY, PH, EH, and SEN, the highest number of QTL was found under low-N environments. No common QTL between optimum and low-N stressed conditions were identified for GY and ASI. For secondary traits, there were some common QTL for optimum and low-N conditions. Most QTL conferring tolerance to N stress was on a different chromosome position under optimum conditions.

Genetic Dissection of Resistance to Gray Leaf Spot by Combining Genome-Wide Association, Linkage Mapping, and Genomic Prediction in Tropical Maize Germplasm

“…An association mapping panel developed at the international Maize and Wheat Improvement Center (CIMMYT), called the Improved Maize for African soils (IMAS) panel (Ertiro et al, 2020a), three doubled haploid (DH) populations [pop1 CML 550 x CML494 (107 lines); pop2 CML550 x CML504 (211 lines); pop3 CML550 x CML511 (107 lines)] (Ertiro et al, 2020b), and two F 3 populations [pop4 CZL0618 x LaPostaSeqC7-F71-1-2-1-1B (183 lines); and pop5 CZL074 x LaPostaSeqC7-F103-1-2-1-1B (172 lines)] (Semagn et al, 2012;Zhang et al, 2015) were used in this study ( Supplementary Table S1). The IMAS panel, comprising 410 CIMMYT maize (sub)tropical inbred lines, was used to evaluate the genetic architecture of resistance to several major diseases through GWAS (Gowda et al, 2015;Sitonik et al, 2019).…”

“…The IMAS panel included lines adapted to tropical lowlands, African mid-elevation/subtropical, and the tropical highlands. All three DH populations used in this study were also used in earlier studies on MLN and low N stress conditions (Sitonik et al, 2019;Ertiro et al, 2020b); the two F 3 populations were used to study the grain yield under optimum and drought stress conditions (Semagn et al, 2012;Zhang et al, 2015). The IMAS panel was evaluated in four location-year combinations [Kakamega (0 • 17 3.19 N 34 • 45 8.24 E, 1535 masl) and Kitale (1.0191 • N 35.0023 • E, 1900 masl) in 2013 and 2014].…”

“…More detailed explanation on the molecular markers used and the linkage map construction for DH and F 3 populations are available in earlier studies (Semagn et al, 2012;Sitonik et al, 2019;Ertiro et al, 2020b). In brief, the DNA of all inbred lines of the IMAS AM panel and the biparental populations was extracted from seedlings at 3-4 leaf stages and genotyped using the GBS platform at the Institute for Genomic Diversity, Cornell University, Ithaca, United States, using high-density markers, as per the procedure described by Elshire et al (2011).…”

Morphological, physiological, and transcriptional responses to low nitrogen stress in Populus deltoides Marsh. clones with contrasting nitrogen use efficiency

“…Although studies on plant responses to low N stress have been carried out at morphological, physiological, and transcriptional levels, most of them were limited to root tissues of a single genotype, such as in maize [ 37 ], rice [ 38 ], and poplar [ 39 ]. However, different genotypes show different tolerances to biotic and abiotic stresses, including low N tolerance [ 36 , 40 ].…”

Dissecting the Genetic Basis of Flowering Time and Height Related-Traits Using Two Doubled Haploid Populations in Maize

“…Of these, qPH_Y1a / q EH_Y1 a spanned the genomic region of 15.6–33.4 Mb on chromosome 1, where the gene ZmRPH1 has been validated to be linked with PH and EH [ 39 ], and another similar QTL was also reported previously in this region [ 29 ]. The qPH_Z1a/qEH_Z1a/qER_Z1a overlapped with a QTL cluster conferring the PH, EH, and AD traits [ 57 ]. Another two repeatedly identified QTLs qPH_Z3a/qEH_Z3a and qPH_Z9a/ qEH_Z9a have not been found to have any major QTLs or genes associated with height traits to the best of our knowledge.…”