Speed Breeding To Accelerate Crop Improvement

: Global food security has become a major issue as the human population grows and the environment changes, with the current rate of improvement of several important crops inadequate to meet future demand. Crop plants have extended generation times, which contribute to the slow rate of progress. However, speed breeding has revolutionized the entire world by reducing generation time and speeding up breeding and research programs to improve crop varieties. In the absence of an integrated pre-breeding program, breeding new and high-performing cultivars with market-preferred traits can take more than ten years. After the first crosses with parental genotypes, a large amount of time, space and resources are committed in the selection and genetic advancement stages during the early stages of breeding. Speed breeding has the ability to shorten the time it takes to develop, market and commercialize cultivars. Crop improvement in the face of a fast changing environment and an ever-increasing human population is a major concern for scientists around the world. Current crop enhancement projects are progressing at a rate that is insufficient to meet food demand. Crop redesign is urgently needed for climate resilience, as well as long-term yield and nutrition. Crop progress is slowed significantly by the long generation time required by crop plants during the breeding process. Speed breeding is now being used on a large scale to shorten generation time and support multiple crop generations per year as a solution in this approach. Researchers are now using an integrated approach to improve breeding efficiency, combining speed breeding with current plant breeding and genetic engineering methods. Speed breeding is a promising approach for achieving nutritional security and sustainable agriculture by shortening breeding cycles for food and industrial crop enhancement. Speed breeding is a methodology that allows plant breeders to improve crop production by adjusting temperature, light duration and intensity to boost plant development. It uses an artificial source of light, which is kept on continuously, to activate the photosynthetic process, which leads to growth and reproduction much earlier than normal. This will assist in meeting the demands of the future's rising population. This can be accomplished using a variety of technologies, including genotyping, marker-assisted selection, high throughput phenotyping, gene editing, genomic selection and re-domestication, all of which can be combined with speed breeding to allow plant breeders to keep up with a changing climate and growing human population.


INTRODUCTION
2050, with freshwater availability declining by up to 50% Crop production must increase to meet the food demands immediate investments in this area, notably in needs of the world human population; yet, changing the development of high-yielding crops that are climate environmental conditions make this task difficult.Climate resilient and use water more effectively and efficiently change, also known as the "climate catastrophe, " is than their current counterparts [2].By 2050, the current causing the Earth to become warmer and drier [1].rate of crop improvement will be insufficient to feed the Drought-related economic losses in agriculture have world's growing population.In the face of drought stress, cost the world $29 billion over the last decade [1].
which results in severe crop yield losses, higher, more Water demand for agriculture is expected to double by stable and sustainable crop production is necessary.
as a result of growing climate variability.Food security The global population has been growing for several labs; it can be done in ordinary settings [7].Speed years and is expected to grow by at least 25% breeding provides various advantages over conventional geometrically, yet food supplies are still limited [3].
approaches, including the ability to accelerate back Traditional or conventional breeding methods will not be crossing, pyramiding characteristics and transgenic sufficient to meet the demands of future generations, so pipelines.Speed breeding can be done in smaller regions breeders and cultivators are constantly under pressure to and researchers who do not have access to bigger areas improve crop production and develop new varieties of can set up smaller speed breeding units [8].To speed crop crop that are of higher quality and yield higher yields that development under controlled temperature and light should be of superior quality in every respect, including conditions, speed breeding has been integrated with nutritional value, disease resistance and climatic changes.numerous different methods.Before an improved cultivar is issued, it must go through Selecting complimentary parental genotypes with several generations of cycling and evaluation.To desired traits followed by crossings and a succession of introduce and assess many traits of interest, this lengthy selection and advancement of superior progenies to procedure is required.However, a process known as ' produce candidate cultivars that meet market demands, speed breeding' for rapid generation advancement has is the traditional strategy of breeding a new crop variety been successfully implemented in agricultural plants to [9].Higher yield potential and nutritional quality, as well achieve rapid rates of crop improvement.Unlike in the as increased tolerance to biotic and abiotic challenges, is past, plant breeders now have breakthrough technology all important breeding goals in agricultural cultivar that can help them overcome future crises and improve improvement projects [9].In any crop improvement crop types.
program, the following breeding procedures can be Some of the methods that are now being used include distinguished in the following order: (a) selection of the development of automated high-throughput desirable parents with complementary traits to combine; phenotyping technology systems that help to boost (b) crosses involving the selected parents and the selection strength and precision [4].Another option is to development of progenies; (c) selection and genetic use 2 and 3 generation sequencing platforms, which advancement of the best progenies based on target traits; nd rd allow breeders to use more economical DNA markers.(d) screening of the best progenies in multiple target It helps in gene discovery and analytical breeding production environments to identify the best performing technologies, both of which attempt to boost production [8].quantity and quality [5].Although all of these Most crop cultivar development efforts use these technologies help to produce the best results, one of their conventional breeding techniques.In the absence of an limitations is that they only produce one or two integrated pre-breeding program, however, traditional generations per year, which poses a problem for crop breeding processes can take more than ten years to production in terms of quantity.However, this limitation produce and release an enhanced variety [10].However, has been alleviated by the 'speed breeding' protocol, current methods such as doubled haploid breeding [11] which uses light and temperature control systems to and speed breeding can minimize the length of each crop produce at least six generations of crops per year [6].
breeding cycle [12].Speed breeding is a collection of Speed breeding has the ability to develop crop strategies that involves manipulating the environmental varieties in a smaller duration of time.It is an artificial conditions in which crop genotypes are produced with environment with increased light duration to provide the goal of speeding up flowering and seed development extended day light, which helps in the manipulation of in order to get to the next breeding generation as soon as photo-insensitive crop life cycles.A new variety takes feasible.Through quick generation development, the 8-10 years to produce using traditional methods, but with approach reduces breeding time and resources.Global speed breeding, the generation cycle can be shortened climate change and population growth have posed a (2-3x times).Speed breeding methods are available for danger to global food security by increasing demand for several plant crops that function on the chromosomes and larger quantity and higher quality food.Crop breeding are provided with ideal light quality, light intensity and attempts to meet this growing need, but the long breeding proper temperature to boost photosynthesis and cycle required to generate any acceptable cultivar is a increase growth and breeding.At least six generations of severe restriction.As a result, breeders have long desired distinct species are produced as a result of this process.
to reduce the crop duration in each generation of a Speed breeding does not necessitate the use of specialist breeding cycle.Speed breeding is a new technology that aims to shorten the agricultural breeding cycle and most effective when targeting a small number of genes accelerate crop improvement through rapid generation with a large effect, such as leaf rust resistance genes (e.g.advancement.Growing crops in a speed breeding-specific Lr23) in bread and durum wheat and Yr15 in durum wheat growth chamber speeds up research on adult plant [16].phenotyping, crossing, mutants and transformation.
Speed breeding produces 3 to 9 generations per year Speed breeding protocols are currently being against 1 to 2 generations per year with traditional developed for several crops [6].Unlike twofold haploid selection methods [6].As a result, speed breeding allows technology, which uses haploid embryos to produce for the rapid production of homozygous and stable entirely homozygous lines, speed breeding is suited for a genotypes, as well as the rapid progress of generations, wide range of germplasm and does not require special in resulting in the development and release of novel vitro culturing equipment [6].The premise of speed cultivars [17].In addition, for multiple trait selection, breeding is to accelerate the rate of photosynthesis by speed breeding technology works well with markerusing optimal light intensity, temperature and daytime assisted selection and high-throughput phenotyping duration regulation (22 h light, 22°C day/17°C night and approaches.Furthermore, marker-assisted selection may high light intensity), along with annual seed harvesting to only be used if the target gene or QTL responsible for the minimize the generation period [13].Flowering is desired characteristic is known.As a result, markercontrolled by the intensity and wavelength of light [14].
assisted selection is less viable for complex traits when The speed of yield increment in most crop breeding the underlying genetic influences are unknown [18].efforts is insufficient to meet the increased food demand Genomic selection (GS) has recently surmounted the induced by a rapidly growing global population.The very constraints of marker-assisted selection by estimating long crop duration limits the development of improved breeding values (EBVs), which provide an assessment of crop varieties in plant breeding.The rapid development of the genomic merit associated with all small or substantial better plant varieties is one strategy to alleviate food impacts across the entire genome, using genome-wide scarcity issues and increase food security.Through rapid markers [19].Genomic selection also allows for generation advancement, speed breeding shortens the simultaneous selection of several traits; nevertheless, breeding cycle and accelerates crop research.Speed despite the efficiency and promise of this breeding breeding can be done in a variety of methods, one of strategy, the costs of genotyping large numbers of which is to lengthen the duration of plants' daily light selection candidates are currently too costly to encourage exposure, paired with early seed harvest, to cycle swiftly widespread usage.Furthermore, because genomic from seed to seed, lowering generation times for some selection is often used to inbred lines [20], the rate of long-day or day-neutral crops.The objective of this paper advancement is constrained by the time necessary to was to assess the potential use of speed breeding conduct crossings and generate genetically stable new techniques in a crop improvement system.selection candidates.This allows breeding programs to save time and money by an inspiration to all plant scientists.Researchers at the reducing labor and field testing costs.A high-throughput, University of Queensland coined the phrase "speed reproducible and robust screening methodology is breeding" in 2003 to describe a set of techniques necessary to accomplish this.For genetic studies and designed to speed up wheat breeding.Over the last 100 plant breeding, improving existing phenotyping methods years, traditional breeding programs around the world and inventing new methods for phenotyping traits is have produced numerous notable enhanced types.

Role of Speed Breeding in Enhancement of
critical.High-throughput, rapid, cost-effective and Despite this, development is gradual, in part due to the repeatable methods are required for traits that are highly lengthy breeding cycle, which can take anywhere from 10 variable not just in the field but also in the glasshouse.to 15 years from cross to cultivar release [15].Combining Speed breeding methods can also be used to synchronize large numbers of polygenic characteristics is a significant the flowering of cultivated and wild individuals of crop challenge [9].While marker-assisted selection has proven species, increasing the amount of variety in breeding to be an effective tool in crop improvement programs, it is populations and accelerating the achievement of breeding technology has proven to be beneficial.Gene editing is a Integrated Phenotyping with Speed Breeding as a Tool a crop species in order to improve its yield.Felix Wolter et for Improving Yield: Any breeding selection method al. [28] investigated the ability of CRISPR/Cas to generate starts with phenotyping.Modern plant phenotyping, directed genomic variation at many loci in their research.on the other hand, evaluates complex traits related to The CRISPR/Cas system opens new possibilities for growth, yield and stress adaption with greater accuracy genetic diversity.It can multiplex, which means that the and precision at many scales of organization, from organs number of targets can be changed at the same time.It to canopies [22].The assessment of complex plant traits addresses the actual issue and a high-yielding variety can such as growth, development, tolerance, resistance, be produced; however, this process takes a long time and architecture, physiology, ecology and yield, as well as the requires a lot of effort; therefore, combining genome basic measurement of individual quantitative parameters editing and speed breeding has the potential to overcome that form the basis for complex trait assessment, is a more this crisis and multiple generations can be produced in a recent and comprehensive definition for plant single year [28].phenotyping [23].The dynamic and local interaction of phenotypes with the spatially and temporally dynamic Boosting Genetic Gain by Speed Breeding and Genomic environment above and below ground gives rise to the Selection: Shorter breeding cycles (the time between plant phenotype.Plant biomass [24], root morphology crossing and selecting progeny to use as parents for the [25], leaf features [26] and fruit traits are all examples of next cross) and a reduction in the number of cycles structural and functional aspects that can be directly required to develop new varieties can help breeders and quantified.
researchers make faster progress.In crops including Phenotyping is the assessment of complex plant wheat, rice and maize, recent improvements in breeding traits related to growth, development and all other techniques such as genetic engineering, genomic features that serve as the foundation for complex trait selection and doubled-haploid technology have assessment.Because the temperature fluctuates shortened breeding cycles and enhanced genetic gain throughout the year in every corner of the world, it has an rates [15].When these technologies are paired with speed impact on crop output, resulting in human misery due to breeding techniques, which allow for rapid generation a lack of food resources.Jack Christopher et al. [27] advancement by cultivating plant populations under conducted an experiment on the Australian environment regulated photoperiod and temperature regimes to because there was evidence of a continual rise in quicken their growth and development, they can have an temperature and decrease in rainfall in that region.As a even bigger impact [28].result, an experiment was carried out to determine the The rate of genetic gain in a breeding program can be efficacy of combining phenotyping and speed represented by the breeder's equation, a model of the breeding to promote root adaptation in changing expected change in a trait in response to selection [29].environments and water scarcity.By combining phenotyping and speed breeding, a multi-purpose approach was used to boost yield.Overpopulation development of more than 1000 recombinant inbred lines of wheat was advanced to generation within 18 months, according to the study's findings.As a result, our study provides a solid foundation for integrating genetic advances toward enhanced adaptability to water-limited conditions [27].

Gene Editing in Combination with Speed Breeding for
Crop Improvement: Although traditional plant breeding technology that involves making changes to the genes of The equation can be written as: where is the change in the trait mean per year, g is the amount of genetic variation within the population, i is the selection intensity, r is the selection accuracy and L is the length of the breeding cycle.Based on this equation, speed breeding protocols can improve genetic gain in crop improvement programs by increasing the number of plant generations cycled in one year, which can substantially reduce the length of the breeding cycle.This is particularly useful for crossing and line development prior to field evaluation.
Speed breeding and genomic selection is used to the ever-increasing food demand for grain crops.It is improve the genetic benefit.Researchers have shown critical to enhance breeding processes in order to boost that speed breeding and genomic selection can improve food production in less time.To increase agricultural genetic benefit in a variety of crops.Meuwissen et al. [30] traits, several conventional and molecular breeding were the first to propose genomic selection.The strategies are applied.CRISPR/Cas9, CRISPR/Cpf1, prime fundamental benefit of using genomic selection is that it editing, base editing, dcas9 epigenetic modification and shortens the breeding cycle and creates higher-quality various additional transgene-free genome editing plant varieties in a shorter amount of time and declining number of plant and animal species and Early hybridization is followed by a selective breeding strains are used in global agri-food systems [35].Shorter approach in this procedure.Plant breeding is especially breeding cycles (the time between crossing and selecting connected to polyploidy crops.It is a time-consuming progeny to use as parents for the next cross) and a technique, thus to address this issue, it has been reduction in the number of cycles required to develop new integrated with speed breeding, which minimizes the time varieties can help breeders and researchers make faster duration and number of generations of that crop that has progress.In crops including wheat, rice and maize, recent been issued.Plant domestication proof has to be found in improvements in breeding techniques such as genetic polyploidy plants like peanuts and bananas, in engineering, genomic selection and doubled-haploid combination with rapid breeding.O'Connora et al. [32] technology have shortened breeding cycles and undertook a study to determine the feasibility of using enhanced genetic gain rates [15].When these the speed breeding approach in peanut breeding.
technologies are paired with speed breeding techniques, In comparison to the regular breeding phase, this study which allow for rapid generation advancement by reduces the time it takes to produce multiple generations cultivating plant populations under regulated photoperiod in a shorter period of time [12].and temperature regimes to hasten their growth and

Multiple Disease Resistance by Speed Breeding:
Plant breeding has played a critical role in ensuring Plant breeders are experimenting with new approaches food security and safety since the early 1900s and has to improve crop production quality in order to respond had a significant impact on food supply around the world faster to changing climates and emerging diseases.[36].However, in recent years, worldwide food quality and Lee T. Hickey et al. [15] combined the two-row barley quantity issues have arisen as a result of the excessive cultivar Scarlett with novel approaches for rapid trait food demand for the fast growing human population.introgression in a study.They developed 87 BC1F3:4 Furthermore, extreme weather changes caused by global Scarlett introgression lines (ILs) in two years using four climate change are generating heat and drought stress, donor lines with multiple disease resistance and a resulting in major crop losses for farmers all over the redesigned backcross method that included phenotypic world [37].Global epidemics, such as the Irish potato multi-trait screens as well as fast generation advance blight of the 1840s and the Southern corn leaf blight of the technology' speed breeding' [33].
1970s in the United States, were terrible events that killed Comparison of Speed Breeding with Others Breeding of food production to consumption has declined Techniques: Plant breeding strategies that use existing significantly in recent years, while worldwide urbanization genomic variation in plants to generate a variety in eight rates and demographic growth have soared.People to ten years can reduce genetic variability in the genome choose to consume processed meals, which have a lower of the plant.Traditional breeding methods cannot meet nutritional content, in this era of rapid expansion and urbanization, extreme and changing climates, the need to development, they can have an even bigger impact [17].
millions of people owing to a lack of food [38].The ratio progress.Traditional farming practices intended to diploid or diploid-like qualities (maize and tomatoes) rather improve the nutritional value of various food plants.
than polyploidy traits (alfalfa and potatoes), which have Recent scientific advancements have opened up a wide more complex genetics.Breeders prefer to use crops with range of plant breeding options and novelties [39].
shorter reproductive cycles, which allow for the To meet the growing demand for plant-based products, production of multiple generations in a single year, the current yearly yield enhancement levels in main crop resulting in faster artificial breeding of desired species (ranging from 0.8-1.2percent) must be doubled phenotypes than crops that reproduce only once a year [40].
or perennial plants that reproduce only once every few (maximum and minimum temperatures) should be using a variety of techniques.Plant breeding has been applied for each crop.Humidity: A reasonable proven to be accelerated using novel strategies range of 60-70% is ideal and for crops adopted in developed in the last decade, including as genomic drier conditions, can apply a lower level.selection, high-throughput phenotyping (HTP) and current speed breeding.Gene transformation has also been used to generate crops with desirable characteristics utilizing genetic engineering and molecular technologies [42].Other strategies have been proposed to improve the breeding of commercially significant crop species, such as cisgenesis, intragenesis, polyploidy breeding and mutant breeding, such as large-scale sequencing, genomics, quick gene isolation and high-throughput molecular markers [43].
Plant genome improvement is insufficient for developing new plant varieties using traditional breeding approaches.Since the 1990s, molecular markers have been employed to identify superior hybrid lines to overcome this barrier in plant breeding procedures [44].The artificial selection and breeding of this provided attribute by the plant breeder is required to improve plant phenotype for   breeding procedures can help to improve the selection of The very long crop duration limits the creation of elite genotypes and lines with innovative features like improved crop types in plant breeding.A new cultivar can improved yield and nutritional quality, as well as biotic take one or two decades to develop due to the numerous and abiotic stress tolerance.The most suitable selection stages of crossing, selection and testing needed in the strategies that is compatible with rapid breeding.generation of new plant varieties.The rapid development However, in many developing countries, particularly in of better plant varieties is one strategy to alleviate food public plant breeding programs, the adoption of speed scarcity issues and increase food security.To improve breeding is limited due to a shortage of skilled plant agronomic qualities in crop plants that is linked to breeders and plant breeding technicians, as well as a lack production, quality and tolerance to biotic and abiotic of the necessary infrastructure and reliable water and challenges.Genetic selection, mutagenic breeding, electricity sources.There is now a lack of regulatory and somaclonal variations, whole-genome sequence-based financial support from the government to launch and techniques, physical mapping and functional genomics continue speed breeding in public plant breeding tools were among the traditional and molecular programs.To accelerate the production, testing and approaches used.Recent advancements in genome commercial release of crop varieties, speed breeding must editing technology, such as programmable nucleases, be combined with other breeding techniques as well as clustered regularly interspaced short palindromic repeats cost-effective high-throughput genotyping and (CRISPR) and CRISPR-associated (Cas) proteins, have phenotyping.In general, plant biologists can scale up ushered in a new era of plant breeding.Plant breeders and their crop improvement research by combining speed researchers around the world are using modern strategies breeding with genetic tools and resources.Speed such as speed breeding, genome editing technologies and breeding protocols that reduce plant production times can high-throughput phenotyping to improve crop breeding help accelerate breeding and research to meet rising efficiency.
demand.Speed breeding is a form of protocol that can be used to increase agricultural yield by altering the light duration, REFERENCES intensity and temperature controlled zone, as well as the generation of disease resistant varieties and lowering salt 1. FAO, 2019.Disasters causing billions in agricultural sensitivity in crops.The photosynthetic process is losses, with drought leading the way.improved via speed breeding, resulting in faster crop www.fao.org/news/story/en/item/1106977/icode/.
approach allows for the release of several generations of Plants: techniques have been established, allowing for the The majority of plant species have bottlenecks in their characterization and selection of important traits [21].applied research and breeding programs, requiring the Plant breeders are interested in screening a wide range of development of technology to speed up plant growth and traits in population development's early generations.generation turnover.NASA's work in the early 1980s was

Fig. 1 :
Fig. 1: Historical milestones in plant breeding.For 10, 000 achieved through light-emitting diodes (LEDs) or years, farmers and breeders have been developing other lighting sources as halogen lamps or sodium and improving crops.vapor lamps (SVLs).In addition to controlling light Presently, farmers feed 10 times more people using of, so the recommended photosynthetic photon the same amount of land as 100 years ago.The use of flux density (PPFD) of ~450-500 µmol/m 2 /s.Mendelian rules to crop breeding transformed the Photoperiod: Normally recommended photoperiod profession.Crop development has changed dramatically of 22 h with 2 h of darkness in a 24-h diurnal cycle. in the last 150 years as a result of cutting-edge genetics Temperature: The optimal temperature regime [41].Plant reproductive cycles have been shortened(maximum and minimum temperatures) should be using a variety of techniques.Plant breeding has been applied for each crop.Humidity: A reasonable proven to be accelerated using novel strategies range of 60-70% is ideal and for crops adopted in developed in the last decade, including as genomic drier conditions, can apply a lower level.selection, high-throughput phenotyping (HTP) and current speed breeding.Gene transformation has also been used to generate crops with desirable characteristics utilizing genetic engineering and molecular technologies[42].Other strategies have been proposed to improve the breeding of commercially significant crop species, such as cisgenesis, intragenesis, polyploidy breeding and mutant breeding, such as large-scale sequencing, genomics, quick gene isolation and high-throughput molecular markers[43].Plant genome improvement is insufficient for developing new plant varieties using traditional breeding approaches.Since the 1990s, molecular markers have been employed to identify superior hybrid lines to overcome this barrier in plant breeding procedures[44].The artificial selection and breeding of this provided attribute by the plant breeder is required to improve plant phenotype for Fig.3: Speed breeding coupled with other breeding a certain desirable trait.In general, breeders focus on methodologies

Fig. 3 :
Speed breeding coupled with other breeding a certain desirable trait.In general, breeders focus on methodologies years [45].