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From Green Super Rice to green agriculture: Reaping the promise of functional genomics research.
Yu, S, Ali, J, Zhou, S, Ren, G, Xie, H, Xu, J, Yu, X, Zhou, F, Peng, S, Ma, L, et al
Molecular plant. 2022;(1):9-26
Abstract
Producing sufficient food with finite resources to feed the growing global population while having a smaller impact on the environment has always been a great challenge. Here, we review the concept and practices of Green Super Rice (GSR) that have led to a paradigm shift in goals for crop genetic improvement and models of food production for promoting sustainable agriculture. The momentous achievements and global deliveries of GSR have been fueled by the integration of abundant genetic resources, functional gene discoveries, and innovative breeding techniques with precise gene and whole-genome selection and efficient agronomic management to promote resource-saving, environmentally friendly crop production systems. We also provide perspectives on new horizons in genomic breeding technologies geared toward delivering green and nutritious crop varieties to further enhance the development of green agriculture and better nourish the world population.
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Rewilding staple crops for the lost halophytism: Toward sustainability and profitability of agricultural production systems.
Rawat, N, Wungrampha, S, Singla-Pareek, SL, Yu, M, Shabala, S, Pareek, A
Molecular plant. 2022;(1):45-64
Abstract
Abiotic stress tolerance has been weakened during the domestication of all major staple crops. Soil salinity is a major environmental constraint that impacts over half of the world population; however, given the increasing reliance on irrigation and the lack of available freshwater, agriculture in the 21st century will increasingly become saline. Therefore, global food security is critically dependent on the ability of plant breeders to create high-yielding staple crop varieties that will incorporate salinity tolerance traits and account for future climate scenarios. Previously, we have argued that the current agricultural practices and reliance on crops that exclude salt from uptake is counterproductive and environmentally unsustainable, and thus called for a need for a major shift in a breeding paradigm to incorporate some halophytic traits that were present in wild relatives but were lost in modern crops during domestication. In this review, we provide a comprehensive physiological and molecular analysis of the key traits conferring crop halophytism, such as vacuolar Na+ sequestration, ROS desensitization, succulence, metabolic photosynthetic switch, and salt deposition in trichomes, and discuss the strategies for incorporating them into elite germplasm, to address a pressing issue of boosting plant salinity tolerance.
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Diverse role of phytic acid in plants and approaches to develop low-phytate grains to enhance bioavailability of micronutrients.
Pramitha, JL, Rana, S, Aggarwal, PR, Ravikesavan, R, Joel, AJ, Muthamilarasan, M
Advances in genetics. 2021;:89-120
Abstract
Natural or synthetic compounds that interfere with the bioavailability of nutrients are called antinutrients. Phytic acid (PA) is one of the major antinutrients present in the grains and acts as a chelator of micronutrients. The presence of six reactive phosphate groups in PA hinders the absorption of micronutrients in the gut of non-ruminants. Consumption of PA-rich diet leads to deficiency of minerals such as iron and zinc among human population. On the contrary, PA is a natural antioxidant, and PA-derived molecules function in various signal transduction pathways. Therefore, optimal concentration of PA needs to be maintained in plants to avoid adverse pleiotropic effects, as well as to ensure micronutrient bioavailability in the diets. Given this, the chapter enumerates the structure, biosynthesis, and accumulation of PA in food grains followed by their roles in growth, development, and stress responses. Further, the chapter elaborates on the antinutritional properties of PA and explains the conventional breeding and transgene-based approaches deployed to develop low-PA varieties. Studies have shown that conventional breeding methods could develop low-PA lines; however, the pleiotropic effects of these methods viz. reduced yield, embryo abnormalities, and poor seed quality hinder the use of breeding strategies. Overexpression of phytase in the endosperm and RNAi-mediated silencing of genes involved in myo-inositol biosynthesis overcome these constraints. Next-generation genome editing approaches, including CRISPR-Cas9 enable the manipulation of more than one gene involved in PA biosynthesis pathway through multiplex editing, and scope exists to deploy such tools in developing varieties with optimal PA levels.
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4.
Snow mold of winter cereals: a complex disease and a challenge for resistance breeding.
Ponomareva, ML, Gorshkov, VY, Ponomarev, SN, Korzun, V, Miedaner, T
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik. 2021;(2):419-433
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Abstract
Snow mold resistance is a complex quantitative trait highly affected by environmental conditions during winter that must be addressed by resistance breeding. Snow mold resistance in winter cereals is an important trait for many countries in the Northern Hemisphere. The disease is caused by at least four complexes of soilborne fungi and oomycetes of which Microdochium nivale and M. majus are among the most common pathogens. They have a broad host range covering all winter and spring cereals and can basically affect all plant growth stages and organs. Their attack leads to a low germination rate, and/or pre- and post-emergence death of seedlings after winter and, depending on largely unknown environmental conditions, also to foot rot, leaf blight, and head blight. Resistance in winter wheat and triticale is governed by a multitude of quantitative trait loci (QTL) with mainly additive effects highly affected by genotype × environment interaction. Snow mold resistance interacts with winter hardiness in a complex way leading to a co-localization of resistance QTLs with QTLs/genes for freezing tolerance. In practical breeding, a multistep procedure is necessary with (1) freezing tolerance tests, (2) climate chamber tests for snow mold resistance, and (3) field tests in locations with and without regularly occurring snow cover. In the future, resistance sources should be genetically characterized also in rye by QTL mapping or genome-wide association studies. The development of genomic selection procedures should be prioritized in breeding research.
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5.
Genome editing of polyploid crops: prospects, achievements and bottlenecks.
Schaart, JG, van de Wiel, CCM, Smulders, MJM
Transgenic research. 2021;(4):337-351
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Abstract
Plant breeding aims to develop improved crop varieties. Many crops have a polyploid and often highly heterozygous genome, which may make breeding of polyploid crops a real challenge. The efficiency of traditional breeding based on crossing and selection has been improved by using marker-assisted selection (MAS), and MAS is also being applied in polyploid crops, which helps e.g. for introgression breeding. However, methods such as random mutation breeding are difficult to apply in polyploid crops because there are multiple homoeologous copies (alleles) of each gene. Genome editing technology has revolutionized mutagenesis as it enables precisely selecting targets. The genome editing tool CRISPR/Cas is especially valuable for targeted mutagenesis in polyploids, as all alleles and/or copies of a gene can be targeted at once. Even multiple genes, each with multiple alleles, may be targeted simultaneously. In addition to targeted mutagenesis, targeted replacement of undesirable alleles by desired ones may become a promising application of genome editing for the improvement of polyploid crops, in the near future. Several examples of the application of genome editing for targeted mutagenesis are described here for a range of polyploid crops, and achievements and bottlenecks are highlighted.
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Crop breeding - From experience-based selection to precision design.
Liu, J, Fernie, AR, Yan, J
Journal of plant physiology. 2021;:153313
Abstract
Crops are the foundation of human society, not only by providing needed nutrition, but also by feeding livestock and serving as raw materials for industry. Cereal crops, which supply most of our calories, have been supporting humans for thousands of years. However food security is facing many challenges nowadays, including growing populations, water shortage, and increased incidence of biotic and abiotic stresses. According to statistical data from the Food and Agriculture Organization of the United Nations (FAO, http://www.fao.org/), the people suffering severe food insecurity increased from 7.9 % in 2015 to 9.7 % in 2019 and the number of people exposed to moderate or severe food insecurity have increased by 400 million over the same time period. Although there are many ways to cope with these challenges, crop breeding remains the most crucial and direct manner. With the development of molecular genetics, the speed of cloning genetic variations underlying corresponding phenotypes of agricultural importance is considerably more rapid. As a consequence breeding methods have evolved from phenotype-based to genome-based selection. In the future, knowledge-driven crop design, which integrates multi-omics data to reveal the connections between genotypes and phenotypes and to build selection models, will undoubtedly become the most efficient way to shape plants, to improve crops, and to ensure food security.
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Base editing in rice: current progress, advances, limitations, and future perspectives.
Yarra, R, Sahoo, L
Plant cell reports. 2021;(4):595-604
Abstract
Base editing is one of the promising genome editing tools for generating single-nucleotide changes in rice genome. Rice (Oryza sativa L.) is an important staple food crop, feeding half of the population around the globe. Developing new rice varieties with desirable agronomic traits is necessary for sustaining global food security. The use of genome editing technologies for developing rice varieties is pre-requisite in the present scenario. Among the genome editing technologies developed for rice crop improvement, base editing technology has emerged as an efficient and reliable tool for precise genome editing in rice plants. Base editing technology utilizes either adenosine or cytidine base editor for precise editing at the target region. A base editor (adenosine or cytidine) is a fusion of catalytically inactive CRISPR/Cas9 domain and adenosine or cytidine deaminase domain. In this review, authors have discussed the different adenine and cytosine base editors developed so far for precise genome editing of rice via base editing technology. We address the current progress, advances, limitations, as well as future perspectives of the base editing technology for rice crop improvement.
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A rapid, simple, and highly efficient method for VIGS and in vitro-inoculation of plant virus by INABS applied to crops that develop axillary buds and can survive from cuttings.
Liu, Q, Xu, K, Yi, L, Hou, Y, Li, D, Hu, H, Zhou, F, Song, P, Yu, Y, Wei, Q, et al
BMC plant biology. 2021;(1):545
Abstract
BACKGROUND Virus-induced gene silencing (VIGS) is one of the most convenient and powerful methods of reverse genetics. In vitro-inoculation of plant virus is an important method for studying the interactions between viruses and plants. Agrobacterium-based infiltration has been widely adopted as a tool for VIGS and in vitro-inoculation of plant virus. Most agrobacterium-based infiltration methods applied to VIGS and virus inoculation have the characteristics of low transformation efficiencies, long plant growth time, large amounts of plant tissue, large test spaces, and complex preparation procedures. Therefore, a rapid, simple, economical, and highly efficient VIGS and virus inoculation method is in need. Previous studies have shown that the selection of suitable plant tissues and inoculation sites is the key to successful infection. RESULTS In this study, Tobacco rattle virus (TRV) mediated VIGS and Tomato yellow leaf curl virus (TYLCV) for virus inoculation were developed in tomato plants based on the agrobacterium tumefaciens-based infiltration by injection of the no-apical-bud stem section (INABS). The no-apical-bud stem section had a "Y- type" asymmetric structure and contained an axillary bud that was about 1-3 cm in length. This protocol provides high transformation (56.7%) and inoculation efficiency (68.3%), which generates VIGS transformants or diseased plants in a very short period (8 dpi). Moreover, it greatly reduces the required experimental space. This method will facilitate functional genomic studies and large-scale disease resistance screening. CONCLUSIONS Overall, a rapid, simple, and highly efficient method for VIGS and virus inoculation by INABS was developed in tomato. It was reasonable to believe that it can be used as a reference for the other virus inoculation methods and for the application of VIGS to other crops (such as sweet potato, potato, cassava and tobacco) that develop axillary buds and can survive from cuttings.
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Plant genome engineering from lab to field-a Keystone Symposia report.
Cable, J, Ronald, PC, Voytas, D, Zhang, F, Levy, AA, Takatsuka, A, Arimura, SI, Jacobsen, SE, Toki, S, Toda, E, et al
Annals of the New York Academy of Sciences. 2021;(1):35-54
Abstract
Facing the challenges of the world's food sources posed by a growing global population and a warming climate will require improvements in plant breeding and technology. Enhancing crop resiliency and yield via genome engineering will undoubtedly be a key part of the solution. The advent of new tools, such as CRIPSR/Cas, has ushered in significant advances in plant genome engineering. However, several serious challenges remain in achieving this goal. Among them are efficient transformation and plant regeneration for most crop species, low frequency of some editing applications, and high attrition rates. On March 8 and 9, 2021, experts in plant genome engineering and breeding from academia and industry met virtually for the Keystone eSymposium "Plant Genome Engineering: From Lab to Field" to discuss advances in genome editing tools, plant transformation, plant breeding, and crop trait development, all vital for transferring the benefits of novel technologies to the field.
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Big genomic data analysis leads to more accurate trait prediction in hybrid breeding for yield enhancement in crop plants.
Singh, RK, Prasad, M
Plant cell reports. 2021;(10):2009-2011
Abstract
The 'big data' in plant breeding refers to the cumulative genotyping and phenotyping information obtained from either a series of experimental sets or generated from a large number of accessions. Recent study supports the employment of big data for enhancing the accuracy of complex trait prediction during hybrid breeding of crop plants.