Thomas Lübberstedt

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• Dr. rer. nat.
• Professor at Iowa State University

Key Message Association mapping of a subset of the SweetCAP diversity panel revealed ten single-nucleotide polymorphisms (SNPs) associated with haploid male fertility (HMF), which provided four candidate genes. Abstract Doubled haploid (DH) technology using in vivo haploid induction has dramatically improved the efficiency of maize breeding progra...

Maize is a key biomass resource with wide agricultural applications. Anthocyanins, potent antioxidants, offer health benefits like reducing oxidative stress. The biosynthesis of anthocyanins competes with that of lignin for shared metabolic precursors, which can lead to trade‐offs in plant growth and feed quality. Higher lignin content can decrease...

Heterosis, a key technology in modern commercial maize breeding, is limited by the narrow genetic base which hinders breeders from developing superior hybrid varieties. By integrating big data and functional genomics technologies, it becomes possible to create new super maize inbred lines that resemble hybrid varieties through the aggregation of mu...

Maize lethal necrosis (MLN) is a significant threat to food security in Sub-Saharan Africa (SSA), with limited commercial inbred lines displaying tolerance. This study analyzed the transcriptomes of four commercially used maize inbred lines and a non-adapted inbred line, all with varying response levels to MLN. RNA-Seq revealed differentially expre...

Key message Restoration of haploid female and haploid male fertility without colchicine is feasible. Three SNPs and eight gene models for HFF, and one SNP and a gene model for HMF were identified. Abstract Doubled haploid (DH) breeding accelerates the development of elite inbred lines and facilitates the incorporation of exotic germplasm, offering...

Shoot apical meristem (SAM) is the origin of aerial structure formation in the plant life cycle. However, the mechanisms underlying the maize SAM development are still obscure. Here, approximately 12 700 cells were captured from the 5‐day‐old shoot apex of maize using a high‐throughput single‐cell transcriptome sequencing. According to the gene exp...

Maize is used for multiple purposes, including food, feed, and energy production, and since transitioning to hybrid cultivars at around 1930, maize yield has significantly increased. This is largely due to hybrid vigor, which refers to the superior performance of the progeny from two unrelated inbred parents. Consequently, nearly all maize cultivar...

Doubled haploid (DH) technology allows for the development of completely homozygous lines from heterozygous plants in only two generations. This approach has been widely adopted in maize breeding programs, as it expedites the generation of inbred lines compared to traditional methods. The DH approach is based on the use of maize genotypes that have...

Key message Parental combinations determined by genomic estimated usefulness and parental contributions of the lines in bridging population can enhance the genetic gain of traits of interest in maternal haploid inducer breeding. Abstract Parent selection in crosses aligns well with the quantitative trait performance in the progenies. We herein tak...

Doubled haploid (DH) breeding accelerates the development of elite inbred lines and facilitates the incorporation of exotic germplasm, offering a powerful tool for maize improvement. Traditional DH breeding relies on colchicine to induce haploid genome doubling. Colchicine is toxic, and its application is labour-intensive, with most genotypes recor...

Polyploidy played an important role in the evolution of the three most important crops: wheat, maize and rice, each of them providing a unique model for studying allopolyploidy, segmental alloploidy or paleopolyploidy. However, its genetic and evolutionary role is still vague. The undelying mechanisms and consequences of polyploidy remain fundament...

Key message The exploration and dissection of a set of QTLs and candidate genes for gray leaf spot disease resistance using two fully assembled parental genomes may help expedite maize resistance breeding. Abstract The fungal disease of maize known as gray leaf spot (GLS), caused by Cercospora zeae-maydis and Cercospora zeina, is a significant con...

Multiple factors can affect the R1-nj purple kernel expression and seed set, reducing its efficiency in identifying haploids in maize. The complex interaction among the haploid inducer (HI), source germplasm (SG), and season (S) is inevitable in in vivo maize haploid induction but could be used through compatibility and stability tests. We tested f...

Genetic gains made by plant breeders are limited by generational cycling rates and flowering time. Several efforts have been made to reduce the time to switch from vegetative to reproductive stages in plants, but these solutions are usually species-specific and require flowering. The concept of in vitro nurseries is that somatic plant cells can be...

Genomic selection and doubled haploids hold significant potential to enhance genetic gains and shorten breeding cycles across various crops. Here, we utilized stochastic simulations to investigate the best strategies for optimize a sweet corn breeding program. We assessed the effects of incorporating varying proportions of old and new parents into...

Key message A large-effect QTL was fine mapped, which revealed 79 gene models, with 10 promising candidate genes, along with a novel inversion. Abstract In commercial maize breeding, doubled haploid (DH) technology is arguably the most efficient resource for rapidly developing novel, completely homozygous lines. However, the DH strategy, using in...

Doubled haploid (DH) line production through in vivo maternal haploid induction is widely adopted in maize breeding programs. The established protocol for DH production includes four steps namely in vivo maternal haploid induction, haploid identification, genome doubling of haploid, and self-fertilization of doubled haploids. Since modern haploid i...

Doubled haploid (DH) technology becomes more routinely applied in maize hybrid breeding. However, some issues in haploid induction and identification persist, requiring resolution to optimize DH production. Our objective was to implement simultaneous marker-assisted selection (MAS) for qhir1 (MTL/ZmPLA1/NLD) and qhir8 (ZmDMP) using TaqMan assay in...

Background Strategies to understand meiotic processes have relied on cytogenetic and mutant analysis. However, thus far in vitro meiosis induction is a bottleneck to laboratory-based plant breeding as factor(s) that switch cells in crops species from mitotic to meiotic divisions are unknown. A high-throughput system that allows researchers to scree...

Haploid inducers are key components of doubled haploid (DH) technology in maize. Robust agronomic performance and better haploid induction ability of inducers are persistently sought through genetic improvement. We herein developed C1-I inducers enabling large-scale in vivo haploid induction of inducers and discovered superior inducers from the DH...

Dramatic improvements in measuring genetic variation across agriculturally relevant populations (genomics) must be matched by improvements in identifying and measuring relevant trait variation in such populations across many environments (phenomics). Identifying the most critical opportunities and challenges in genome to phenome (G2P) research is t...

Key message Employing multi-trait and de novo GWAS in a ridge regression BLUP model increases the predictive ability of haploid induction rate of haploid inducers in maize. Ridge regression BLUP (rrBLUP) is a widely used model for genomic selection. Different genomic prediction (GP) models have their own niches depending on the genetic architecture...

Selection in the Iowa Stiff Stalk Synthetic (BSSS) maize population for high yield, grain moisture, and root and stalk lodging has indirectly modified plant architecture traits that are important for adaptation to high plant density. In this study, we developed doubled haploid (DH) lines from the BSSS maize population in the earliest cycle of recur...

Nitrogen (N) limits crop production, yet more than half of N fertilizer inputs are lost to the environment. Developing maize hybrids with improved N use efficiency can help minimize N losses and in turn reduce adverse ecological, economical, and health consequences. This study aimed to identify single nucleotide polymorphisms (SNPs) associated with...

In maize, doubled haploid (DH) lines are created in vivo through crosses with maternal haploid inducers. Their induction ability, usually expressed as haploid induction rate (HIR), is known to be under polygenic control. Although two major genes (MTL and ZmDMP) affecting this trait were recently described, many others remain unknown. To identify th...

Molecular characterization of a given set of maize germplasm could be useful for understanding the use of the assembled germplasm for further improvement in a breeding program, such as analyzing genetic diversity, selecting a parental line, assigning heterotic groups, creating a core set of germplasm and/or performing association analysis for trait...

Efforts to increase genetic gains in breeding programs of flowering plants depend on making genetic crosses. Time to flowering, which can take months to decades depending on the species, can be a limiting factor in such breeding programs. It has been proposed that the rate of genetic gain can be increased by reducing the time between generations by...

Introduction Computer vision and deep learning (DL) techniques have succeeded in a wide range of diverse fields. Recently, these techniques have been successfully deployed in plant science applications to address food security, productivity, and environmental sustainability problems for a growing global population. However, training these DL models...

In vivo maternal haploid induction in isolation fields is proposed to bypass the workload and resource constraints existing in haploid induction nurseries. A better understanding of combining ability and gene action conditioning traits related to hybrid inducers is necessary to set the breeding strategy including to what extent parent-based hybrid...

Key message Combined GWAS, WGCNA, and gene-based association studies identified the co-expression network and hub genes for maize EC induction. ZmARF23 bound to ZmSAUR15 promoter and regulated its expression, affecting EC induction. Abstract Embryonic callus (EC) induction in immature maize embryos shows high genotype dependence, which limits the...

Dramatic improvements in measuring genetic variation across agriculturally relevant populations (genomics) must be matched by improvements in identifying and measuring relevant trait variation in such populations across many environments (phenomics). Identifying the most critical opportunities and challenges in the area of genome to phenome (G2P) r...

The effectiveness of haploid induction systems is regarded not only for high haploid induction rate (HIR) but also resource savings. Isolation fields are proposed for hybrid induction. However, efficient haploid production depends on inducer traits such as high HIR, abundant pollen production, and tall plants. Seven hybrid inducers and their respec...

Doubled haploid technology can accelerate plant breeding and its two main steps are haploid induction and subsequent doubled haploid production from fertile haploid plants. Although haploid female fertility is present to some extent in plants, the lack of haploid male fertility is a bottleneck. Herein, we demonstrate that mutations in the parallel...

Self-incompatibility (SI) is a genetic mechanism of hermaphroditic plants to prevent inbreeding after self-pollination. Allogamous Poaceae species exhibit a unique gametophytic SI system controlled by two multi-allelic and independent loci, S and Z. Despite intense research efforts in the last decades, the genes that determine the initial recogniti...

Computer vision and deep learning (DL) techniques have succeeded in a wide range of diverse fields. Recently, these techniques have been successfully deployed in plant science applications to address food security, productivity, and environmental sustainability problems for a growing global population. However, training these DL models often necess...

Drought is an important constraint to agricultural productivity worldwide and is expected to worsen with climate change. To assist farmers, especially in sub-Saharan Africa (SSA), to adapt to climate change, continuous generation of stress-tolerant and farmer-preferred crop varieties, and their adoption by farmers, is critical to curb food insecuri...

Tropicalization is one of the major objectives in breeding haploid inducers to address the poor adaptation of temperate haploid inducers in doubled haploid production in tropical maize. Gaining a better understanding of weather profiles in targeted agroecology is important. This study aimed to investigate the seasonal variation of tropical savanna...

Extensive lead (Pb) accumulation in plants exerts toxic effects on plant growth and development and enters the human food chain. Combining linkage mapping, transcriptome analysis, and association studies, we cloned the ZmbZIP54 transcription factor, which confers maize tolerance to Pb. Combined overexpression and knockdown confirmed that ZmbZIP54 m...

The ability of immature embryos to induce embryogenic callus (EC) is crucial for genetic transformation in maize, which is highly genotype-dependent. To dissect the genetic basis of maize EC induction, we conducted QTL mapping for four EC induction-related traits, the rate of embryogenic callus induction (REC), rate of shoot formation (RSF), length...

Self-incompatibility (SI) is a genetic mechanism of hermaphroditic plants to prevent inbreeding after self-pollination. Allogamous Poaceae species exhibit a unique gametophytic SI system controlled by two multiallelic and independent loci, S and Z . Despite intense research efforts in the last decades, the genes that determine the initial recogniti...

Doubled haploid technology is a feasible, fast, and cost-efficient way of producing completely homozygous lines in maize. Many factors contribute to the success of this system including the haploid induction rate (HIR) of inducer lines, the inducibility of donor background, and environmental conditions. Sixteen inducer lines were tested on eight di...

Key message Spontaneous haploid genome doubling is not associated with undesirable linkage drag effects. The presence of spontaneous doubling genes allows maximum exploitation of variability from the temperate-adapted BS39 population Abstract Tropical non-elite maize (Zea mays L.) germplasm, such as BS39, provides a unique opportunity for broadeni...

The identification of genomic regions associated with root traits and the genomic prediction of untested genotypes can increase the rate of genetic gain in maize breeding programs targeting roots traits. Here, we combined two maize association panels with different genetic backgrounds to identify SNPs significantly associated with root traits and t...

Key message MADS26 affecting maize seed germination was identified by GWAS and transcriptomics. Gene-based association analyses revealed three variations within MADS26 regulating seed germination traits. Overexpressed MADS26 in Arabidopsis improved seed germination. Abstract Seed germination ability is extremely important for maize production. Exp...

Doubled haploid (DH) technology in maize takes advantage of in vivo haploid induction (HI) triggered by pollination of donors of interest with inducer genotypes. However, the ability of different donors to be induced—inducibility (IND), varies among germplasm and the underlying molecular mechanisms are still unclear. In this study, the phenotypic v...

Extensive lead (Pb) absorption by plants affects their growth and development and causes damage to the human body by entering the food chain. In this study, we cloned ZmHIPP, a gene associated with Pb tolerance and accumulation in maize, using combined linkage mapping and weighted gene co-expression network analysis. We show that ZmHIPP, which enco...

Chilling injury poses a serious threat to seed emergence of spring-sowing maize in China, which has become one of the main climatic limiting factors affecting maize production in China. It is of great significance to mine the key genes controlling low-temperature tolerance during seed germination and study their functions for breeding new maize var...

Doubled haploid (DH) technology reduces the time required to obtain homozygous genotypes and accelerates plant breeding among other advantages. It is established in major crop species such as wheat, barley, maize, and canola. DH lines can be produced by both in vitro and in vivo methods and the latter is focused here. The major steps involved in in...

Multi-trait selection helps breeders identify genotypes that appeal to divergent groups of preferences. In this study, we performed simultaneous selection of sweet-waxy corn hybrids on several traits covering the perspectives of consumers (taller kernel depth, better eating quality), growers (early maturity, shorter plant stature, and high ear yiel...

Lacking elite haploid inducers performing high haploid induction rate (HIR) and agronomic performance is one of fundamental factors hindering the rapid adoption of doubled haploid technology in maize hybrid breeding, especially under tropical savanna climate. Breeding haploid inducers for specific agro-ecology, thus, is indispensable yet challengin...

Sterols are integral components of membrane lipid bilayers in eukaryotic organisms and serve as precursors to steroid hormones in vertebrates and brassinosteroids (BR) in plants. In vertebrates, cholesterol is the terminal sterol serving both indirect and direct roles in cell signaling. Plants synthesize a mixture of sterols including cholesterol,...

Self-incompatibility (SI) is a genetic mechanism preventing self-pollination in ~40% of plant species. Two multiallelic loci, called S and Z, control the gametophytic SI system of the grass family (Poaceae), which contains all major forage grasses. Loci independent from S and Z have been reported to disrupt SI and lead to self-compatibility (SC). A...

The study aimed to improve the small-ear waxy corn populations for prolificacy, high total carotenoid content and resistance to downy mildew. Three cycles of modified mass selection were carried out for population improvement. Forty-four genotypes derived from eight C3 populations and six check varieties were evaluated for agronomic traits and yiel...

Adapted exotic maize ( Zea mays L.) germplasm, such as BS39, provides a unique opportunity for broadening the genetic base of U.S. Corn Belt germplasm. In vivo doubled haploid (DH) technology has been used to efficiently exploit exotic germplasm. It can help to purge deleterious recessive alleles. The objectives of this study were to determine the...

Keymessage Two hub genes GRMZM2G075104 and GRMZM2G333183 involved in salt tolerance were identified by GWAS and WGCNA. Furthermore, they were verified to affect salt tolerance by candidate gene association analysis. AbstractSalt stress influences maize growth and development. To decode the genetic basis and hub genes controlling salt tolerance is a...

The heavy metals lead and cadmium have become important pollutants in the environment, which exert negative effects on plant morphology, growth and photosynthesis. It is particularly significant to uncover the genetic loci and the causal genes for lead and cadmium tolerance in plants. This study used an IBM Syn10 DH population to identify the quant...

Key message A major locus for spontaneous haploid genome doubling was detected by a case–control GWAS in an exotic maize germplasm. The combination of double haploid breeding method with this locus leads to segregation distortion on genomic regions of chromosome five. Abstract Temperate maize (Zea mays L.) breeding programs often rely on limited g...

Self-incompatibility (SI) is a genetic mechanism preventing self-pollination in approximately 40% of plant species. Two multiallelic loci, called S and Z , control the gametophytic SI system of the grass family (Poaceae), which contains all major forage grasses. Loci independent from S and Z have been reported to disrupt SI and lead to self-compati...

Background Self-incompatibility (SI) systems prevent self-fertilisation in several species of Poaceae, many of which are economically important forage, bioenergy and turf grasses. SI ensures cross-pollination and genetic diversity but restricts the ability to fix useful genetic variation. In most inbred crops, it is possible to develop high perform...

Salt stress influences maize growth and development. To decode the genetic basis and hub genes controlling salt tolerance is a meaningful exploration for cultivating salt-tolerant maize varieties. Herein, we used an association panel consisting of 305 lines to identify the genetic loci responsible for Na ⁺ - and K ⁺ -related traits in maize seedlin...

Waxy corn is a popular, alternative staple food in most Asian countries including Thailand. The availability of small-ear waxy corn genotypes with prolific ears and a high level of carotenoids is expected to benefit growers and consumers. Integrated evaluation among source germplasm is essential before performing further breeding efforts for enhanc...

In arid or semi‐arid regions, deep‐sowing is an effective treasure to ensure seeds absorbing water from deep soil layer at present. However, the existing maize varieties have poor tolerance to deep‐sowing, which is attributed to that few genes are explored and utilised. In this study, 243 IBM Syn4 recombinant inbred lines (RIL) constructed with B73...

Doubled haploids (DHs) are an important breeding tool for creating maize inbred lines. One bottleneck in the DH process is the manual separation of haploids from among the much larger pool of hybrid siblings in a haploid induction cross. Here, we demonstrate the ability of single‐kernel near‐infrared reflectance spectroscopy (skNIR) to identify hap...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The purpose of this study was to examine the genotypic variation in maize doubled haploid (DH) lines response to brassinosteroid and gibberellin inhibitors. Plant responses to hormone inhibitors were determined in growth chamber experiments using germination paper for three different seedling treatments: application of propiconazole (Pcz), uniconaz...

Key message: A major QTL for SHGD was identified on chromosome 5 with stable expression across environments. The introgression this QTL can overcome the need of colchicine in DH lines development. Genome doubling of haploids is one of the major constraints of large-scale doubled haploid (DH) technology. Improving spontaneous haploid genome doublin...

Maize (Zea mays L.) inbred lines with expired Plant Variety Protection Act (ExPVP) certificates are publicly available and potentially represent a new germplasm resource for many public and private breeding programs. The use of these inbred lines for maize breeding in sub‐Saharan African (SSA) was little investigated. Hence, this study was conducte...

Doubled haploid technology is highly successful in maize breeding programs and is contingent on the ability of maize inducers to efficiently produce haploids. Knowledge of the genes involved in haploid induction is important for not only developing better maize inducers, but also to create inducers in other crops. The main quantitative trait loci i...

Maize doubled haploid (DH) lines are usually created in vivo, through crosses with maternal haploid inducers. These inducers have the inherent ability of generating seeds with haploid embryos when used to pollinate other genotypes. The resulting haploid plants are treated with a doubling agent and self-pollinated, producing completely homozygous se...

The elite maize hybrid Zhengdan 958 (ZD958), which has high and stable yield and extensive adaptability, is widely grown in China. To elucidate the genetic basis of yield and its related traits in this elite hybrid, a set of doubled haploid (DH) lines derived from ZD958 were evaluated in four different environments at two locations over two years,...

Genomic prediction (GP) might be an efficient way to improve haploid induction rate (HIR) and to reduce the laborious and time‐consuming task of phenotypic selection for HIR in maize (Zea mays L.). In this study, we evaluated GP accuracies for HIR and other agronomic traits of importance to inducers by independent and cross‐validation. We propose t...

Doubled haploid (DH) technology has changed the maize-breeding landscape in recent years. Traditionally, DH production requires the use of chemical doubling agents to induce haploid genome doubling and, subsequently, male fertility. These chemicals can be harmful to humans and the plants themselves, and typically result in a doubling rate of 10%–30...

Doubled haploid (DH) lines are used in maize (Zea mays L.) breeding to accelerate the breeding cycle and create homogenous inbred lines in as little as two seasons. These pure inbred lines allow breeders to quickly evaluate new cross combinations. There are two important steps in creating DH lines: (a) generation and selection of haploid progeny, a...

Kernel abortion is common phenomenon in vivo haploid induction and closely linked with haploid induction rate, but little information of kernel abortion is available and its genetic basis still unclear. We used two mapping populations including 186 and 263 F2.3 family lines to analyze the different degree of kernel abortion and identify quantitativ...

Key message High-density haplotype analysis revealed significant haplotype sharing between ex-PVPs registered from 1976 to 1992 and key maize founders, and uncovered similarities and differences in haplotype sharing patterns by company and heterotic group. Abstract Proprietary inbreds developed by the private seed industry have been the major sour...

Key message Candidate genes on grain drying rate (GDR) were identified, and drying molecular mechanism of grain was explored by integrating genome-wide association with transcriptomic analysis in maize. Abstract Grain drying rate (GDR) is a key determinant of grain moisture at harvest. Here, a genome-wide association study (GWAS) of 309 inbred mai...

Root system architecture (RSA) contributes to nitrogen (N) uptake and utilization in maize. In this study, a germplasm enhancement of maize double haploid population of 226 lines genotyped with 61,634 SNPs was used to investigate the genetic basis of RSA under two N levels using a genome-wide association study (GWAS). GLM + PCA, FarmCPU, and MLM mo...