Breeding Field Crops, Fifth Edition, thoroughly covers the field of plant breeding. The latest edition of this venerable text provides a broad overview of the science of plant breeding, and provides students and breeders with essential fundamental information along with a review of current breakthroughs and technologies. This book will be a valuable source of information for anyone involved in the science of plant breeding for years to come.
The focus of Field Crops Research is crop ecology, crop physiology, agronomy, and crop improvement of field crops for food, fibre, feed and biofuel. The inclusion of yield data is encouraged to demonstrate how the field experiments contribute to the understanding of the bio-physical processes related to crop growth, development and the formation and realisation of yield.Articles on quality (grain, fibre, fodder), breeding and genetics, crop protection (diseases, pests, weeds), phenotyping, remote and non-contact sensing, soils, climate and greenhouse gas emissions, are encouraged, provided they are integrated with crop ecology, crop physiology, crop improvement and/or agronomy.Articles containing new insights into resource-use efficiency, crop intensification, precision and digital agriculture, climate smart practices and molecular and/or physiological breeding are welcome.Studies at lower levels of organisation (plant to molecular) must demonstrate scaling up to crop level or higher.
Research that is corroborative, descriptive, or only of local significance. Studies carried-out exclusively under controlled-environment (greenhouse, pot, or any system that constricts root growth) conditions.Studies on natural grasslands, horticultural (i.e., vegetable and fruit species), woody perennial and non-cultivated species. One-year field studies in one location or environment.Articles on crop storage, transportation and usage, and social studies on crops and cropping systems.
Papers must demonstrate new scientific insight, original technologies or novel methods that have general application and relevance to field crops. Research findings of a purely corroborative nature, descriptive or of only local significance will not be considered.
Field experiments on which manuscripts are based should, unless exceptional circumstances apply, include at least two seasons and/or multiple locations/environments. The inclusion of yield data is highly encouraged to demonstrate how the field experiments contribute to a better understanding of the bio-physical processes related to crop growth. Papers on crop protection (diseases, pests, weeds) can be accepted provided they have a strong focus on crop processes, including consequences for yield. Experiments under controlled conditions (glasshouse, growth chamber) are only acceptable as complementary to field work; studies carried-out exclusively under controlled conditions are outside the scope of the journal. Articles on crop storage, transportation and usage, and social studies on crops and cropping systems, are outside the scope of the journal.
Development of crops over time, including a the loss of the diversity through the genetic bottlenecks of domestication, selection of landraces and modern plant breeding (adapted from , with permission from AAAS), and b example of a tall wheat landrace grown prior to the Green Revolution (left) and a modern high yielding cultivar selected for reduced plant height (right)
The plant kingdom is extremely complex and the optimal plant breeding strategy is highly species-dependant. However, any breeding program can be broadly classed into three main processes: i) the creation of new genetic variation, ii) the selection of candidates based on defined merits and iii) the testing, propagation and release of improved crop varieties. The conventional way of creating new genetic variation is to make targeted crosses between selected individuals to create progeny that segregate for the trait of interest, typically representing the start of a breeding program. After that, a main task of the breeder is to identify genetically superior individuals from typically large populations (thousands to tens of thousands of genotypes). This typically involves multi-year and -location testing of candidates in replicated experimental field trials in order to estimate the genetic potential of a genotype across a range of growing conditions as accurately as possible. It is important to consider that most important crop species can be propagated as inbred lines or clones, thereby allowing repeated testing of the same genotype in different production conditions. For most important crop species, modern selection strategies have been developed that incorporate genome information based on next-generation DNA sequencing technologies in the breeding process (see below). In the final stage, breeders will typically register their most promising variety candidates (typically only one or two) at a legal variety testing department that runs multi-year and -location evaluation trials to assess if the variety has distinctly improved characteristics that warrant its official registration. Once registered, the new variety becomes available to farmers. Depending on the crop this process can take up to one to two decades, making breeding programs very rigid and complex endeavours.
Biofortified crops generated by different approaches: transgenic, agronomic, and breeding. Staple cereals, most common vegetables, beans, and fruits have been targeted by all three approaches. Some crops have been targeted by only one or two approaches depending on its significance and prevalence in the daily human diet.
Representation of reported biofortified crops by transgenic, agronomic, and breeding means. (A) Comparison of transgenic and breeding approaches of biofortification in terms of relative research and release of commercial crops. While higher emphasis is being laid on transgenic-based biofortification, success rate in terms of cultivar release is higher for breeding-based approach. (B) Percentage of different crops biofortified by different approaches. Cereals have been biofortified in largest number by all three biofortification approaches. Legumes and vegetables have also been targeted by all the approaches in almost equal percentage. Transgenic approach covers highest number of crops. Oilseed crops have been mainly targeted by transgenic approaches due to limited genetic variability.
To meet increasing global food demand, breeders and scientists aim to improve the yield and quality of major food crops. Plant diseases threaten food security and are expected to increase because of climate change. CRISPR genome-editing technology opens new opportunities to engineer disease resistance traits. With precise genome engineering and transgene-free applications, CRISPR is expected to resolve the major challenges to crop improvement. Here, we discuss the latest developments in CRISPR technologies for engineering resistance to viruses, bacteria, fungi, and pests. We conclude by highlighting current concerns and gaps in technology, as well as outstanding questions for future research.
Crop varieties have conventionally been developed by farmers and crop breeders using basic techniques such as the selection of plants with desirable characteristic for propagation. Modern plant breeding techniques added marker-assisted selection and genetic modification to the crop improvement toolkit. These methods have been reviewed elsewhere [8, 9]. Briefly, a genetically modified (GM) crop variety is developed by (1) identification of a piece of DNA that confers the trait of interest, for example, a gene responsible for virus resistance; (2) cloning of the DNA into the carrier or vector plasmid; (3) delivery of the DNA to the target plant; and (4) generation of modified plants with the desired trait, e.g., virus resistance. GM crop production has been controversial mainly because of fear-based agricultural policies driven by limited public understanding, ineffective information sharing by scientists, and inaccurate portrayals by NGOs and anti-GM lobbyists . Apart from social and economic concerns such as ownership, stewardship, product regulation, and market development, one major concern related to GM crops is the extensive use of certain agrochemicals (such as glyphosate) in conjunction with herbicide-tolerant GM crop varieties and the retention of antibiotic-resistance genes from the production pipeline in the GM variety. These concerns have led to the enactment of strict regulations for GM crops, which not only make the end products expensive but also slow the delivery of new varieties to farmers, making it more difficult for breeders to produce varieties suited to current threats to crops.
While society remains divided over the use of GM crops, new plant breeding technologies (NPBTs) have recently emerged as alternative approaches to speed up the introduction of improved traits. NPBTs include precision genome-modification platforms such as the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein (Cas) and transcription activator-like effector nuclease (TALEN) methodologies . In addition to genome editing, NPBTs include technological advances that shorten the breeding cycles and accelerate crop research, such as speed breeding [12, 13] and next-generation genotyping  and phenotyping platforms . For some important crops that have a flowering behavior difficult for breeding (such as cassava, Manihot esculenta) or are sterile (such as banana, Musa acuminata), genome editing provides an efficient and robust breeding approach, given the alternative breeding approaches are either significantly inefficient or not applicable .
Notably, the CRISPR/Cas system has emerged as the leading, ground-breaking SSN and, although its utility for plant genome editing was first demonstrated only in 2013 [29,30,31], its applications in plants have increased rapidly compared to other NPBTs. Research using CRISPR has introduced important agricultural traits including heat, cold, and herbicide tolerance; viral, bacterial, and fungal resistance; and increased grain size and weight into many economically important crops, such as rice (Oryza sativa), wheat (Triticum aestivum), maize (Z. mays), tomato (Solanum lycopersicum), potato (Solanum tuberosum), tobacco (Nicotiana tabacum), cotton (Gossypium spp.), soybean (Glycine max), and brassicas . Importantly, several groups have recently accomplished those genome alterations using transgene-free systems. 2b1af7f3a8