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1.
Maize endosperm development.
Dai, D, Ma, Z, Song, R
Journal of integrative plant biology. 2021;(4):613-627
Abstract
Recent breakthroughs in transcriptome analysis and gene characterization have provided valuable resources and information about the maize endosperm developmental program. The high temporal-resolution transcriptome analysis has yielded unprecedented access to information about the genetic control of seed development. Detailed spatial transcriptome analysis using laser-capture microdissection has revealed the expression patterns of specific populations of genes in the four major endosperm compartments: the basal endosperm transfer layer (BETL), aleurone layer (AL), starchy endosperm (SE), and embryo-surrounding region (ESR). Although the overall picture of the transcriptional regulatory network of endosperm development remains fragmentary, there have been some exciting advances, such as the identification of OPAQUE11 (O11) as a central hub of the maize endosperm regulatory network connecting endosperm development, nutrient metabolism, and stress responses, and the discovery that the endosperm adjacent to scutellum (EAS) serves as a dynamic interface for endosperm-embryo crosstalk. In addition, several genes that function in BETL development, AL differentiation, and the endosperm cell cycle have been identified, such as ZmSWEET4c, Thk1, and Dek15, respectively. Here, we focus on current advances in understanding the molecular factors involved in BETL, AL, SE, ESR, and EAS development, including the specific transcriptional regulatory networks that function in each compartment during endosperm development.
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2.
Nitrogen fixation in maize: breeding opportunities.
Sheoran, S, Kumar, S, Kumar, P, Meena, RS, Rakshit, S
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik. 2021;(5):1263-1280
Abstract
Maize (Zea mays L.) is a highly versatile crop with huge demand of nitrogen (N) for its growth and development. N is the most essential macronutrient for crop production. Despite being the highest abundant element in the atmosphere (~ 78%), it is scarcely available for plant growth. To fulfil the N demand, commercial agriculture is largely dependent on synthetic fertilizers. Excessive dependence on inorganic fertilizers has created extensive ecological as well as economic problems worldwide. Hence, for a sustainable solution to nitrogenous fertilizer use, development of biological nitrogen fixation (BNF) in cereals will be the best alternative. BNF is a well-known mechanism in legumes where diazotrophs convert atmospheric nitrogen (N≡N) to plant-available form, ammonium (NH4+). From many decades, researchers have dreamt to develop a similar symbiotic partnership as in legumes to the cereal crops. A large number of endophytic diazotrophs have been found associated with maize. Elucidation of the genetic and molecular aspects of their interaction will open up new avenues to introgress BNF in maize breeding. With the advanced understanding of N-fixation process, researchers are at a juncture of breeding and engineering this symbiotic relationships in cereals. Different breeding, genetic engineering, omics, gene editing, and synthetic biology approaches will be discussed in this review to make BNF a reality in cereals. It will help to provide a road map to develop/improve the BNF in maize to an advance step for the sustainable production system to achieve the food and nutritional security.
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3.
Hyperspectral reflectance-based phenotyping for quantitative genetics in crops: Progress and challenges.
Grzybowski, M, Wijewardane, NK, Atefi, A, Ge, Y, Schnable, JC
Plant communications. 2021;(4):100209
Abstract
Many biochemical and physiological properties of plants that are of interest to breeders and geneticists have extremely low throughput and/or can only be measured destructively. This has limited the use of information on natural variation in nutrient and metabolite abundance, as well as photosynthetic capacity in quantitative genetic contexts where it is necessary to collect data from hundreds or thousands of plants. A number of recent studies have demonstrated the potential to estimate many of these traits from hyperspectral reflectance data, primarily in ecophysiological contexts. Here, we summarize recent advances in the use of hyperspectral reflectance data for plant phenotyping, and discuss both the potential benefits and remaining challenges to its application in plant genetics contexts. The performances of previously published models in estimating six traits from hyperspectral reflectance data in maize were evaluated on new sample datasets, and the resulting predicted trait values shown to be heritable (e.g., explained by genetic factors) were estimated. The adoption of hyperspectral reflectance-based phenotyping beyond its current uses may accelerate the study of genes controlling natural variation in biochemical and physiological traits.
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4.
Successes and insights of an industry biotech program to enhance maize agronomic traits.
Simmons, CR, Lafitte, HR, Reimann, KS, Brugière, N, Roesler, K, Albertsen, MC, Greene, TW, Habben, JE
Plant science : an international journal of experimental plant biology. 2021;:110899
Abstract
Corteva Agriscience™ ran a discovery research program to identify biotech leads for improving maize Agronomic Traits such as yield, drought tolerance, and nitrogen use efficiency. Arising from many discovery sources involving thousands of genes, this program generated over 3331 DNA cassette constructs involving a diverse set of circa 1671 genes, whose transformed maize events were field tested from 2000 to 2018 under managed environments designed to evaluate their potential for commercialization. We demonstrate that a subgroup of these transgenic events improved yield in field-grown elite maize breeding germplasm. A set of at least 22 validated gene leads are identified and described which represent diverse molecular and physiological functions. These leads illuminate sectors of biology that could guide crop improvement in maize and perhaps other crops. In this review and interpretation, we share some of our approaches and results, and key lessons learned in discovering and developing these maize Agronomic Traits leads.
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5.
Microbiome for sustainable agriculture: a review with special reference to the corn production system.
Jat, SL, Suby, SB, Parihar, CM, Gambhir, G, Kumar, N, Rakshit, S
Archives of microbiology. 2021;(6):2771-2793
Abstract
Microbial diversity formed by ages of evolution in soils plays an important role in sustainability of crop production by enriching soil and alleviating biotic and abiotic stresses. This diversity is as an essential part of the agro-ecosystems, which is being pushed to edges by pumping agrochemicals and constant soil disturbances. Consequently, efficiency of cropping system has been decreasing, aggravated further by the increased incidence of abiotic stresses due to changes in climatic patterns. Thus, the sustainability of agriculture is at stake. Understanding the microbiota inhabiting phyllosphere, endosphere, spermosphere, rhizosphere, and non-rhizosphere, and its utilization could be a sustainable crop production strategy. This review explores the available information on diversity of beneficial microbes in agricultural ecosystem and synthesizes their commercial uses in agriculture. Microbiota in agro-ecosystem works by nutrient acquisition, enhancing nutrient availability, water uptake, and amelioration of abiotic and abiotic stresses. External application of such beneficial microbiota or microbial consortia helps in boosting plant growth and provides resistance to drought, salinity, heavy metal, high-temperature and radiation stress in various crop plants. These have been instrumental in enhancing tolerance to diseases, insect pest and nematodes in various cropping system. However, studies on the microbiome in revolutionary production systems like conservation agriculture and protected cultivation, which use lesser agrochemicals, are limited and if exploited can provide valuable input in sustainable agriculture production.
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6.
Beat the stress: breeding for climate resilience in maize for the tropical rainfed environments.
Prasanna, BM, Cairns, JE, Zaidi, PH, Beyene, Y, Makumbi, D, Gowda, M, Magorokosho, C, Zaman-Allah, M, Olsen, M, Das, A, et al
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik. 2021;(6):1729-1752
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Abstract
Intensive public sector breeding efforts and public-private partnerships have led to the increase in genetic gains, and deployment of elite climate-resilient maize cultivars for the stress-prone environments in the tropics. Maize (Zea mays L.) plays a critical role in ensuring food and nutritional security, and livelihoods of millions of resource-constrained smallholders. However, maize yields in the tropical rainfed environments are now increasingly vulnerable to various climate-induced stresses, especially drought, heat, waterlogging, salinity, cold, diseases, and insect pests, which often come in combinations to severely impact maize crops. The International Maize and Wheat Improvement Center (CIMMYT), in partnership with several public and private sector institutions, has been intensively engaged over the last four decades in breeding elite tropical maize germplasm with tolerance to key abiotic and biotic stresses, using an extensive managed stress screening network and on-farm testing system. This has led to the successful development and deployment of an array of elite stress-tolerant maize cultivars across sub-Saharan Africa, Asia, and Latin America. Further increasing genetic gains in the tropical maize breeding programs demands judicious integration of doubled haploidy, high-throughput and precise phenotyping, genomics-assisted breeding, breeding data management, and more effective decision support tools. Multi-institutional efforts, especially public-private alliances, are key to ensure that the improved maize varieties effectively reach the climate-vulnerable farming communities in the tropics, including accelerated replacement of old/obsolete varieties.
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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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9.
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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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.