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1.
The Past, Present, and Future of Maize Improvement: Domestication, Genomics, and Functional Genomic Routes toward Crop Enhancement.
Liu, J, Fernie, AR, Yan, J
Plant communications. 2020;(1):100010
Abstract
After being domesticated from teosinte, cultivated maize (Zea mays ssp. mays) spread worldwide and now is one of the most important staple crops. Due to its tremendous phenotypic and genotypic diversity, maize also becomes to be one of the most widely used model plant species for fundamental research, with many important discoveries reported by maize researchers. Here, we provide an overview of the history of maize domestication and key genes controlling major domestication-related traits, review the currently available resources for functional genomics studies in maize, and discuss the functions of most of the maize genes that have been positionally cloned and can be used for crop improvement. Finally, we provide some perspectives on future directions regarding functional genomics research and the breeding of maize and other crops.
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Dissipation behavior, residues distribution and dietary risk assessment of tembotrione and its metabolite in maize via QuEChERS using HPLC-MS/MS technique.
Su, Y, Wang, W, Hu, J, Liu, X
Ecotoxicology and environmental safety. 2020;:110187
Abstract
The dissipation and residues of tembotrione in corn field application were investigated using liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The average recoveries of tembotrione in maize, corncob, and straw were in the ranges of 98-107% with relative standard deviations (RSDs ≤9.3%), respectively. The recoveries of M5 was in the ranges of 90-108% in all three matrices of maize, with RSDs were 3.3-12.8%. The LODs for tembotrione and M5 in maize were 0.85 μg/L and 1.0 μg/L, 0.84 μg/L and 0.43 μg/L in corncob, 0.94 μg/L and 1.5 μg/L in straw, respectively. The LOQs of the method in maize grain, corncob and straw were 0.01, 0.01 and 0.05 mg/kg for both analytes, respectively. The dissipation of tembotrione in straw was in compliance with the first-order dynamic equation, with half-lives of 1.18-1.23 days at Beijing and Heilongjiang. Total residue of tembotrione in maize grain and corncob matrix were both below 0.02 mg/kg, lower than the max residue limit (MRL) recommended by european food safety authority (EFSA). Risk quotients (RQs) of this pesticide was assessed via comparing national estimated daily intake with acceptable daily intake. The dietary intake risk of tembotrione residue in maize was very low for all groups of Chinese residents. These data could provide scientific data and strategies and facilitate Chinese government to establish the MRLs of tembotrione.
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3.
Ten Years of the Maize Nested Association Mapping Population: Impact, Limitations, and Future Directions.
Gage, JL, Monier, B, Giri, A, Buckler, ES
The Plant cell. 2020;(7):2083-2093
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Abstract
It has been just over a decade since the release of the maize (Zea mays) Nested Association Mapping (NAM) population. The NAM population has been and continues to be an invaluable resource for the maize genetics community and has yielded insights into the genetic architecture of complex traits. The parental lines have become some of the most well-characterized maize germplasm, and their de novo assemblies were recently made publicly available. As we enter an exciting new stage in maize genomics, this retrospective will summarize the design and intentions behind the NAM population; its application, the discoveries it has enabled, and its influence in other systems; and use the past decade of hindsight to consider whether and how it will remain useful in a new age of genomics.
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4.
Recent developments in stigma maydis polysaccharides: Isolation, structural characteristics, biological activities and industrial application.
Zhang, Y, Wang, C, Liu, C, Wang, X, Chen, B, Yao, L, Qiao, Y, Zheng, H
International journal of biological macromolecules. 2020;:246-252
Abstract
Stigma maydis, an ingredient of pharmaceuticals and healthy foods, has a long history of usage in China and some occidental countries. Polysaccharide (SMP) is supposed to be one of the major bioactive compounds in stigma maydis, which possesses immune-enhancement, antitumor, antioxidant, anti-fatigue, diuretic, liver protection, antihyperglycaemic and hypolipidemic activities. In this review, the current advancements on extraction, purification, structural characteristics and biological activities of polysaccharides were summarized. Their biological activities were introduced on the basis of vivo experiments, and some possible mechanisms were listed. Furthermore, industrial application of SMPs were reviewed and discussed. New perspectives for the future work of stigma maydis polysaccharide were also proposed.
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5.
Maize lethal necrosis (MLN): Efforts toward containing the spread and impact of a devastating transboundary disease in sub-Saharan Africa.
Boddupalli, P, Suresh, LM, Mwatuni, F, Beyene, Y, Makumbi, D, Gowda, M, Olsen, M, Hodson, D, Worku, M, Mezzalama, M, et al
Virus research. 2020;:197943
Abstract
Maize lethal necrosis (MLN), a complex viral disease, emerged as a serious threat to maize production and the livelihoods of smallholders in eastern Africa since 2011, primarily due to the introduction of maize chlorotic mottle virus (MCMV). The International Maize and Wheat Improvement Center (CIMMYT), in close partnership with national and international partners, implemented a multi-disciplinary and multi-institutional strategy to curb the spread of MLN in sub-Saharan Africa, and mitigate the impact of the disease. The strategy revolved around a) intensive germplasm screening and fast-tracked development and deployment of MLN-tolerant/resistant maize hybrids in Africa-adapted genetic backgrounds; b) optimizing the diagnostic protocols for MLN-causing viruses, especially MCMV, and capacity building of relevant public and private sector institutions on MLN diagnostics and management; c) MLN monitoring and surveillance across sub-Saharan Africa in collaboration with national plant protection organizations (NPPOs); d) partnership with the private seed sector for production and exchange of MLN pathogen-free commercial maize seed; and e) awareness creation among relevant stakeholders about MLN management, including engagement with policy makers. The review concludes by highlighting the need to keep continuous vigil against MLN-causing viruses, and preventing any further spread of the disease to the major maize-growing countries that have not yet reported MLN in sub-Saharan Africa.
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Doubled haploid technology for line development in maize: technical advances and prospects.
Chaikam, V, Molenaar, W, Melchinger, AE, Boddupalli, PM
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik. 2019;(12):3227-3243
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Abstract
Increased efficiencies achieved in different steps of DH line production offer greater benefits to maize breeding programs. Doubled haploid (DH) technology has become an integral part of many commercial maize breeding programs as DH lines offer several economic, logistic and genetic benefits over conventional inbred lines. Further, new advances in DH technology continue to improve the efficiency of DH line development and fuel its increased adoption in breeding programs worldwide. The established method for maize DH production covered in this review involves in vivo induction of maternal haploids by a male haploid inducer genotype, identification of haploids from diploids at the seed or seedling stage, chromosome doubling of haploid (D0) seedlings and finally, selfing of fertile D0 plants. Development of haploid inducers with high haploid induction rates and adaptation to different target environments have facilitated increased adoption of DH technology in the tropics. New marker systems for haploid identification, such as the red root marker and high oil marker, are being increasingly integrated into new haploid inducers and have the potential to make DH technology accessible in germplasm such as some Flint, landrace, or tropical material, where the standard R1-nj marker is inhibited. Automation holds great promise to further reduce the cost and time in haploid identification. Increasing success rates in chromosome doubling protocols and/or reducing environmental and human toxicity of chromosome doubling protocols, including research on genetic improvement in spontaneous chromosome doubling, have the potential to greatly reduce the production costs per DH line.
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Maize reproductive development and kernel set under limited plant growth environments.
Borrás, L, Vitantonio-Mazzini, LN
Journal of experimental botany. 2018;(13):3235-3243
Abstract
Maize grain yield is highly related to the number of kernels that are established during the flowering period. Kernel number depends on the accumulation of ear biomass and the efficiency of using this biomass for kernel set. Ear biomass depends on the rate of plant biomass accumulation and the proportion of this biomass that is allocated to the ear. In contrast to other major crops, the proportion of plant biomass that is allocated to the ear is not constant in maize, being almost zero under stress conditions. Fortunately, there is wide native genetic variability for this trait, with major practical implications for crop management and plant breeding. Conditions that inhibit plant growth commonly delay silk appearance relative to male anthesis. Time to silking and silk extrusion, which is a tissue expansion process, is dependent on water turgor and ear biomass accumulation, and the magnitude of this delay is used as a marker to phenotype for stress susceptibility. Ear biomass accumulation can also be used for predicting the number of silks that have been extruded if genotype-specific parameters are known. Here, several mechanistic plant and canopy traits are described, together with their implications for better understanding maize yield determination under limited plant growth environments. An ideal genotype sustains growth in environments with limited water or nutrients, has uniform canopies, has increased biomass partitioning to the ear at reduced plant growth, reaches silking with minimum ear biomass, and has rapid silk extrusion for minimizing developmental delays between competing structures within the ear. All these traits help maximize kernel set and yield at limited plant growth, and most have been indirectly selected by breeders when increasing yield.
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Maize domestication and gene interaction.
Stitzer, MC, Ross-Ibarra, J
The New phytologist. 2018;(2):395-408
Abstract
Contents Summary 395 I. Introduction 395 II. The genetic basis of maize domestication 396 III. The tempo of maize domestication 401 IV. Genetic interactions and selection during maize domestication 401 V. Gene networks of maize domestication alleles 404 VI. Implications of gene interactions on evolution and selection404 VII. Conclusions 405 Acknowledgements 405 References 405 SUMMARY Domestication is a tractable system for following evolutionary change. Under domestication, wild populations respond to shifting selective pressures, resulting in adaptation to the new ecological niche of cultivation. Owing to the important role of domesticated crops in human nutrition and agriculture, the ancestry and selection pressures transforming a wild plant into a domesticate have been extensively studied. In Zea mays, morphological, genetic and genomic studies have elucidated how a wild plant, the teosinte Z. mays subsp. parviglumis, was transformed into the domesticate Z. mays subsp. mays. Five major morphological differences distinguish these two subspecies, and careful genetic dissection has pinpointed the molecular changes responsible for several of these traits. But maize domestication was a consequence of more than just five genes, and regions throughout the genome contribute. The impacts of these additional regions are contingent on genetic background, both the interactions between alleles of a single gene and among alleles of the multiple genes that modulate phenotypes. Key genetic interactions include dominance relationships, epistatic interactions and pleiotropic constraint, including how these variants are connected in gene networks. Here, we review the role of gene interactions in generating the dramatic phenotypic evolution seen in the transition from teosinte to maize.
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Developing and deploying climate-resilient maize varieties in the developing world.
Cairns, JE, Prasanna, BM
Current opinion in plant biology. 2018;(Pt B):226-230
Abstract
In sub-Saharan Africa (SSA) and Asia maize yields remain variable due to climate shocks. Over the past decade extensive progress has been made on the development and delivery of climate-resilient maize. In 2016 over 70000 metric tonnes of drought-tolerant maize seed was commercialized in 13 countries in SSA, benefiting an estimated 53 million people. Significant progress is also being made with regard to the development and deployment of elite heat-tolerant maize varieties in South Asia. Increased genetic gain in grain yield under stress-prone environments, coupled with faster replacement of old/obsolete varieties, through intensive engagement with seed companies is essential to protect maize crops grown by smallholders from the changing climates in SSA and Asia.
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10.
Next-Generation Sequencing Promoted the Release of Reference Genomes and Discovered Genome Evolution in Cereal Crops.
Huang, Y, Liu, H, Xing, Y
Current issues in molecular biology. 2018;:37-50
Abstract
In recent decades, next-generation sequencing (NGS) was developed and brought biology into a new era. Rice, maize, wheat, sorghum and barley are the most important cereal crops and feed most of the world's population. Great progress in the study of cereal genomes has been made with the help of NGS. Reference genome sequence assembly and re-sequencing have grown exponentially. Thus, evolution and comparative genomics are renewed, including origin verification, evolution tracking and so on. In this review, we briefly record the development of sequencing technology, the comparison of next-generation sequencing methods and platforms and summarize the bioinformatics tools used for NGS data analysis. We describe how NGS accelerates reference genome assembly and new evolutionary findings. We finally discuss how to discover more valuable resources and improve cereal breeding in the future.