Embracing native diversity to enhance the maximum quantum efficiency of photosystem II in maize.

The sustainability of maize cultivation would benefit tremendously from early sowing, but is hampered by low temperatures during early development in temperate climates. We show that allelic variation within the gene encoding subunit M of the NADH-dehydrogenase-like (NDH) complex (ndhm1) in a European maize landrace affects several quantitative traits that are relevant during early development in cold climates through NDH-mediated cyclic electron transport (CET) around photosystem I, a process crucial for photosynthesis and photoprotection. Beginning with a genome-wide association study for maximum potential quantum yield of photosystem II in dark-adapted leaves (Fv/Fm), we capitalized on the large phenotypic effects of a hAT transposon insertion in ndhm1 on multiple quantitative traits (early plant height, Fv/Fm, chlorophyll content, and cold tolerance) caused by the reduced protein levels of NDHM and associated NDH components.

Effectiveness of introgression of resistance loci for Gibberella ear rot from two European flint landraces into adapted elite maize (Zea mays L.).

European flint landraces are a major class of maize possessing favorable alleles for improving host resistance to Gibberella ear rot (GER) disease which reduces yield and contaminates the grains with mycotoxins. However, the incorporation of these landraces into breeding programs requires a clear understanding of the effectiveness of their introgression into elite materials. We evaluated 15 pre-selected doubled haploid (DH) lines from two European flint landraces, "Kemater Landmais Gelb" (KE) and "Petkuser Ferdinand Rot" (PE), together with two adapted elite flint lines and seven standard lines for GER severity as the main trait, and several adaptation traits (plant height, days to silking, seed-set, plant vigor) across four environments.

Natural alleles of the abscisic acid catabolism gene ZmAbh4 modulate water use efficiency and carbon isotope discrimination in maize.

Altering plant water use efficiency (WUE) is a promising approach for achieving sustainable crop production in changing climate scenarios. Here, we show that WUE can be tuned by alleles of a single gene discovered in elite maize (Zea mays) breeding material. Genetic dissection of a genomic region affecting WUE led to the identification of the gene ZmAbh4 as causative for the effect.

Physiological adaptive traits are a potential allele reservoir for maize genetic progress under challenging conditions.

Combined phenomic and genomic approaches are required to evaluate the margin of progress of breeding strategies. Here, we analyze 65 years of genetic progress in maize yield, which was similar (101 kg ha year) across most frequent environmental scenarios in the European growing area. Yield gains were linked to physiologically simple traits (plant phenology and architecture) which indirectly affected reproductive development and light interception in all studied environments, marked by significant genomic signatures of selection.

Genetic diversity of European maize landraces: Dataset on the molecular and phenotypic variation of derived doubled-haploid populations.

Genetic variation is the basis of selection, evolution and breeding. Maize landraces represent a rich source of allelic diversity, but their efficient utilization in breeding and research has been hampered by their heterogeneous and heterozygous nature and insufficient information about most accessions. While molecular inventories of germplasm repositories are growing steadily, linking these data to meaningful phenotypes for quantitative traits is challenging.

Theoretical and experimental assessment of genome-based prediction in landraces of allogamous crops.

Discovery and enrichment of favorable alleles in landraces are key to making them accessible for crop improvement. Here, we present two fundamentally different concepts for genome-based selection in landrace-derived maize populations, one based on doubled-haploid (DH) lines derived directly from individual landrace plants and the other based on crossing landrace plants to a capture line. For both types of populations, we show theoretically how allele frequencies of the ancestral landrace and the capture line translate into expectations for molecular and genetic variances.

Exploiting genetic diversity in two European maize landraces for improving Gibberella ear rot resistance using genomic tools.

High genetic variation in two European maize landraces can be harnessed to improve Gibberella ear rot resistance by integrated genomic tools. Fusarium graminearum (Fg) causes Gibberella ear rot (GER) in maize leading to yield reduction and contamination of grains with several mycotoxins. This study aimed to elucidate the molecular basis of GER resistance among 500 doubled haploid lines derived from two European maize landraces, "Kemater Landmais Gelb" (KE) and "Petkuser Ferdinand Rot" (PE).

Discovery of beneficial haplotypes for complex traits in maize landraces.

Genetic variation is of crucial importance for crop improvement. Landraces are valuable sources of diversity, but for quantitative traits efficient strategies for their targeted utilization are lacking. Here, we map haplotype-trait associations at high resolution in ~1000 doubled-haploid lines derived from three maize landraces to make their native diversity for early development traits accessible for elite germplasm improvement.

Intercontinental trials reveal stable QTL for Northern corn leaf blight resistance in Europe and in Brazil.

NCLB is the most devastating leaf disease in European maize, and the introduction of Brazilian resistance donors can efficiently increase the resistance levels of European maize germplasm. Northern corn leaf blight (NCLB) is one of the most devastating leaf pathogens in maize (Zea mays L.).

European maize landraces made accessible for plant breeding and genome-based studies.

Doubled-haploid libraries from landraces capture native genetic diversity for a multitude of quantitative traits and make it accessible for breeding and genome-based studies. Maize landraces comprise large allelic diversity. We created doubled-haploid (DH) libraries from three European flint maize landraces and characterized them with respect to their molecular diversity, population structure, trait means, variances, and trait correlations.

Carbon isotope composition, water use efficiency, and drought sensitivity are controlled by a common genomic segment in maize.

A genomic segment on maize chromosome 7 influences carbon isotope composition, water use efficiency, and leaf growth sensitivity to drought, possibly by affecting stomatal properties. Climate change is expected to decrease water availability in many agricultural production areas around the globe. Therefore, plants with improved ability to grow under water deficit are urgently needed.

Genome-Wide Analysis of Yield in Europe: Allelic Effects Vary with Drought and Heat Scenarios.

Assessing the genetic variability of plant performance under heat and drought scenarios can contribute to reduce the negative effects of climate change. We propose here an approach that consisted of (1) clustering time courses of environmental variables simulated by a crop model in current (35 years × 55 sites) and future conditions into six scenarios of temperature and water deficit as experienced by maize (Zea mays L.) plants; (2) performing 29 field experiments in contrasting conditions across Europe with 244 maize hybrids; (3) assigning individual experiments to scenarios based on environmental conditions as measured in each field experiment; frequencies of temperature scenarios in our experiments corresponded to future heat scenarios (+5°C); (4) analyzing the genetic variation of plant performance for each environmental scenario.

First steps to understand heat tolerance of temperate maize at adult stage: identification of QTL across multiple environments with connected segregating populations.

Dents were more heat tolerant than Flints. QTL for heat tolerance with respect to grain yield at field conditions were identified considering multiple populations and environments. High temperatures have the potential to cause severe damages to maize production.

Two major quantitative trait loci controlling the number of seminal roots in maize co-map with the root developmental genes rtcs and rum1.

The genetic dissection of root architecture and functions allows for a more effective and informed design of novel root ideotypes and paves the way to evaluate their effects on crop resilience to a number of abiotic stresses. In maize, limited attention has been devoted to the genetic analysis of root architecture diversity at the early stage. The difference in embryonic (including seminal and primary) root architecture between the maize reference line B73 (which mostly develops three seminal roots) and the landrace Gaspé Flint (with virtually no seminal roots) was genetically dissected using a collection of introgression lines grown in paper rolls and pots.

The maize disease resistance gene Htn1 against northern corn leaf blight encodes a wall-associated receptor-like kinase.

Northern corn leaf blight (NCLB) caused by the hemibiotrophic fungus Exserohilum turcicum is an important foliar disease of maize that is mainly controlled by growing resistant maize cultivars. The Htn1 locus confers quantitative and partial NCLB resistance by delaying the onset of lesion formation. Htn1 represents an important source of genetic resistance that was originally introduced from a Mexican landrace into modern maize breeding lines in the 1970s.

Improving resistance to the European corn borer: a comprehensive study in elite maize using QTL mapping and genome-wide prediction.

The efficiency of marker-assisted selection for native resistance to European corn borer stalk damage can be increased when progressing from a QTL-based towards a genome-wide approach. Marker-assisted selection (MAS) has been shown to be effective in improving resistance to the European corn borer (ECB) in maize. In this study, we investigated the performance of whole-genome-based selection, relative to selection based on individual quantitative trait loci (QTL), for resistance to ECB stalk damage in European elite maize.

Selection strategies for the development of maize introgression populations.

Introgression libraries are valuable resources for QTL detection and breeding, but their development is costly and time-consuming. Selection strategies for the development of introgression populations with a limited number of individuals and high-throughput (HT) marker assays are required. The objectives of our simulation study were to design and compare selection strategies for the development of maize introgression populations of 100 lines with population sizes of 360-720 individuals per generation for different DH and S2 crossing schemes.

Stable carbon isotope discrimination is under genetic control in the C4 species maize with several genomic regions influencing trait expression.

In plants with C4 photosynthesis, physiological mechanisms underlying variation in stable carbon isotope discrimination (Δ(13)C) are largely unknown, and genetic components influencing Δ(13)C have not been described. We analyzed a maize (Zea mays) introgression library derived from two elite parents to investigate whether Δ(13)C is under genetic control in this C4 species. High-density genotyping with the Illumina MaizeSNP50 Bead Chip was used for a detailed structural characterization of 89 introgression lines.

Key impact of Vgt1 on flowering time adaptation in maize: evidence from association mapping and ecogeographical information.

An association study conducted on 375 maize inbred lines indicates a strong relationship between Vgt1 polymorphisms and flowering time, extending former quantitative trait loci (QTL) mapping results. Analysis of allele frequencies in a landrace collection supports a key role of Vgt1 in maize altilatitudinal adaptation.

Quantitative trait loci for early plant vigour of maize grown in chilly environments.

Maize (Zea mays L.) is particularly sensitive to chilling in the early growth stages. The objective of this study was to determine quantitative trait loci (QTL) for early plant vigour of maize grown under cool and moderately warm conditions in Central Europe.

Effects of introgression and recombination on haplotype structure and linkage disequilibrium surrounding a locus encoding Bymovirus resistance in barley.

We present a detailed analysis of linkage disequilibrium (LD) in the physical and genetic context of the barley gene Hv-eIF4E, which confers resistance to the barley yellow mosaic virus (BYMV) complex. Eighty-three SNPs distributed over 132 kb of Hv-eIF4E and six additional fragments genetically mapped to its flanking region were used to derive haplotypes from 131 accessions. Three haplogroups were recognized, discriminating between the alleles rym4 and rym5, which each encode for a spectrum of resistance to BYMV.