Domestication is a process of bringing wild plants (or animals) under human management for betterment of social animals and humans in general. This co-evolutionary process leads to origin of new species or differentiated populations that helps critically in human survival. Darwin’s early models of evaluation was dependent on selection and variations occurred due to domestication. Especially, crop domestications are results of process, from arising as a wild plant (animal), cultivation in new selective environment, adaptation to usage by humans. It plays an important role in survival and fitness of Homo sapience by co-evaluation and propagated under human manipulated environment. The results of domestications are not only one sided, it’s mutual and resulted in increased fitness, population size and species area expansion (outside center of origin). Unlike domesticated animals, plants are evident to play role in hybridization (inter/intra specific) and origin of cultivated many food crop species (rice, wheat, banana, citrus etc.). In the past a few decades, plant breeding has advanced faster and better with the new age technologies like genetic engineering, biotechnology, genome editing etc. We are getting clear understanding that domestication is the foundation base for evolution, diversity, diversification, climate resilient cultivars and food security. It hasn’t only led to develop new plant species or varieties with better quantitative and quality traits but it also enables breeders and farmers to cultivate crops outside area of its origin, which contributes to food security and sustainable agriculture.
Pre-breeding plays a critical role in enhancing crop improvement by integrating desirable traits from wild and un adapted genetic sources into current breeding lines. This chapter underscores the significance of pre-breeding as a crucial link between gene banks, which house diverse genetic materials and plant breeding programs focused on developing new crop varieties. Core strategies involve the characterization of landrace populations, developing new parent populations, and the introgression of beneficial traits through various breeding methodologies. Understanding the gene pool concept is essential for sourcing genetic diversity. Pre-breeding encompasses techniques such as gene pyramiding, mutagenesis, polyploidy, genetic mapping, and the advancement of breeding technologies, including molecular markers and genetic transformation. The primary objective is to boost genetic diversity, enhance crop resilience to environmental stresses, and meet global agricultural demands by combining traditional breeding methods with modern molecular tools. Looking ahead, there is a pressing need for the collection and characterization of wild species, comprehensive gene/genome mapping, and the use of bioinformatics to address complex traits in crop improvement.
This chapter presents an extensive review of traditional plant breeding approaches utilized in improvement of crops with respect to self-pollinated and cross-pollinated crops. It covers key methodologies, including conventional breeding methods like pure-line selection, mass selection, and pedigree methods, as well as more advanced strategies such as recurrent selection, hybridization, and backcross methods separately. The conventional approaches emphasize the selection of phenotypically, superior plants to enhance traits such as yield, resistance to diseases, and adaptability to abiotic conditions, while maintaining genetic diversity. The document also explores the use of hybridization to exploit heterosis, the development of synthetic varieties, and the application of recurrent selection for specific and general combining ability. Furthermore, it discusses the limitations, advantages, and practical applications of each method, offering insights into their effectiveness in addressing contemporary agricultural challenges such as climate change and pest resistance. The detailed procedures, achievements, and potential for further improvement in crop varieties are highlighted, underscoring the critical role of these breeding strategies in ensuring sustainable agriculture and food security.
Organisms categorised as polyploids are those that possess more chromosomal sets than diploid organisms and are categorised as either euploid or aneuploid. In addition to happening naturally, antimitotic agents can also be used for artificial polyploidization. Natural hybridization between species with varying ploidy levels can result in the formation of polyploids. Flow cytometry analysis is the most widely utilised technique for identification of polyploidy. One important mechanism for adaptation and speciation is polyploidy. Artificial polyploidization has increasingly become a prominent strategy in plant mutation breeding as it involves mutation of genome which results in greater phenotypic variation. In this chapter, techniques of polyploidization and effect of polyploidization in different crops will be discussed.
Ensuring global food security depends substantially on plant breeding. Mutation breeding, one of several plant breeding techniques, has improved crops significantly and considerably more quickly than traditional breeding. Mutation breeding techniques especially gamma and other physical mutagens have helped in generating a large number of mutants and generated a massive quantity of genetic variability that is significantly employed in plant breeding, genetics and genomics. Mutation induction may be the only non-GM mechanism for introducing a new characteristic if the desired gene is absent from the germplasm and the only straightforward method to improve seedless crops and cultivars. Many potent physical and chemical mutagens have been identified and developed since the initial reports of induced mutagenesis using x-rays were published, and techniques for applying them in seed and vegetatively propagated crops have been devised. Because of significant developments in plant molecular biology and biotechnology, particularly in the field of plant genomics, we are currently witnessing new impulses in plant mutation research, ranging from basic studies of mutagenesis to reverse genetics. This chapter offers a thorough analysis of what is now known about the various mutagenic agents, mutation breeding techniques, and effects they have on varietal development.
Modern plant breeding aims to increase crop productivity at a rate more phenomenal than previous achievements. According to several research groups addressing this problem, the solution is to produce more biomass through improved photosystem biochemistry, greater assimilation of assimilates to the economically valuable portion of the plant, and increased light use efficiency, but a form of unanimity appears to exist. This chapter draws attention to the concept of heterosis and how it manifests itself in maize, sorghum, and other crops, through various models, in which higher biomass and yield have been obtained, depending on its association with plant breeding concepts such as combining ability and mitochondrial inheritance. Heterosis is employed extensively nowadays without fully grasping the underlying genetic and molecular principles to classify the species into different heterotic groups. Thus, a significant finding that would completely transform plant breeding today would be the comprehension and prediction of the genetic and epigenetic underpinnings governing heterosis.
Forward genetics involves identifying and characterizing genes responsible for observed mutant phenotypes. The process begins with observing or measuring a phenotype, followed by mapping the genes or loci causing the phenotype. This method is unbiased in gene identification since it focuses primarily on the phenotype. In contrast, reverse genetics begin with a known gene and examines the resulting phenotype after the gene's disruption. To generate random mutations in organisms, techniques like ultraviolet irradiation, X-rays and chemical treatments are used. Molecular markers which can measure the genetic variation across the genome were used to distinguish different strains. Advances in technology and genomic knowledge have expanded the sources of these markers. Thus, in plant breeding, forward genetics is vital in identifying genes associated with desirable traits, while reverse genetics is important for validating gene functions and developing crops with targeted improvements.
Doubled haploids (DH) have become a helpful tool for both basic and applied research. The primary, though not exclusive, regular utilization of double haploids by breeding industries is to produce pure lines for seed production among various crops. After many decades of finding of haploid inducer lines in maize and to develop haploid plants from its pollen precursors anther culture was used, with other biotechnological advance tools have helped to develop various techniques for DH production. It is now feasible to make haploids and DH in various species, as there are multiple methods to test if one does not work effectively. This chapter provides an overview of the recent approaches to producing haploids and DHs, by using in vitro, in vivo or using both techniques for embryo formation.
Molecular markers have revolutionized crop improvement by enabling the accurate and efficient selection of desirable traits. This chapter provides a comprehensive overview of the role of molecular markers in plant breeding, emphasizing their use in disease resistance, tolerance to abiotic stress, and improving quality traits. The chapter delves into various types of molecular markers, including RFLPs, RAPDs, AFLPs, SSRs, SNPs, and their respective advantages and limitations in breeding programs. It also explores marker-assisted selection and genomic selection as key strategies for accelerating the breeding process. The combination of molecular markers with traditional breeding methods is explored, with case studies illustrating the effective use of these tools in advancing crop improvement. The chapter concludes by emphasizing the potential of molecular markers to enhance crop resilience and productivity in the face of global challenges, such as climate change and food security.
Nanotechnology is increasingly recognised as a transformative force in the food industry and agriculture. Nanoparticles possess unique properties, including a high surface-to-volume ratio, small size, enhanced solubility and distinct optical, chemical, and magnetic characteristics, which make them highly beneficial in agriculture. The integration of nanotechnology in agriculture is gaining importance due to its potential to reduce agricultural inputs, improve food quality and nutritional content and prolong the shelf life and freshness of food products. Nanomaterials are utilised in preservation and packaging to prevent gas penetration and enhance the absorption of micronutrients and antioxidants. These nanoparticles have documented positive effects on crop plants, significantly enhancing seed germination rates, shoot and root lengths, fruit yields, and metabolite content. They also positively influence biochemical parameters crucial for plant growth and development, such as enhancing photosynthetic rates and nitrogen use efficiency across various crops. Nanoscale materials offer advanced capabilities, including programmed, time-controlled, target-specific, and self-regulated functions. Engineered nanoparticles (ENPs) enable precise, "on-demand" delivery of agrochemicals, meeting nutritional needs or protecting against pathogens and pests while minimising the negative impacts of traditional agrochemicals on both plants and the environment. Moreover, nanoparticles enable the precise delivery of diverse phytoactive molecules, such as proteins and nucleotides, facilitating the modulation of plant metabolism and genetic modifications. This targeted approach opens up new possibilities for enhancing plant traits and improving agricultural productivity. In summary, nanotechnology in agriculture holds immense promise for sustainable and efficient crop production, with applications ranging from disease suppression and crop growth enhancement to precision farming and advanced gene transfer techniques.
Biofortification is a sustainable agricultural technique that aims to improve the nutritional content of staple crops in order to alleviate micronutrient deficiencies, sometimes known as hidden hunger, which impact millions of people throughout the world. This procedure uses advanced breeding techniques such as conventional breeding, Marker-Assisted Selection (MAS), and genetic engineering to boost the concentrations of important vitamins and minerals in crops such as rice, wheat, maize, and cassava. Biofortification, which focuses on important minerals such as iron, zinc, and vitamin A, is a cost-effective and scalable option for improving public health, particularly in developing nations with limited access to diverse meals and fortified foods. Recent advancements in genomic tools, gene editing technologies like CRISPR/Cas9, and metabolic engineering have accelerated the development of biofortified crops with enhanced nutrient profiles and resilience to environmental stresses. Biofortification, as a supplemental strategy to standard nutrition interventions, has the potential to considerably reduce the burden of micronutrient deficiencies, hence improving health outcomes and meeting global food security and nutrition goals.
Gene silencing is a natural process which effectively hinders the expression of an identifiable gene. The primary cause of gene silence is the cytoplasmic presence of double-stranded RNA (dsRNA). Depending on the fundamental principles of molecular genetics, there are two types of gene silencing that occur in plants, of which post-transcriptional gene silencing (PTGS), occurs in cytoplasm and degrades or obstructs some genes' mRNA transcripts. RNAi and asRNA are two examples of PTGS methods (Animasaun et al., 2023). Antisense RNA technology is a novel approach to precisely modify or block gene expression in vitro or in vivo. By forming base pair with the sense RNA strand (mRNA), the antisense strand inhibits sense RNA from being translated into a protein. Thus, antisense technology uses complementary nucleic acid sequences, or antisense compounds, to suppress gene expression. Antisense nucleic acid sequences can bind or hybridize to a particular mRNA target to prevent normal gene expression. This may interfere with transcription or translation, which would prevent the information flow from DNA to protein(Crooke et al., 2021).RNAi involves sequence-specific gene regulation by small non-coding RNA (miRNA, siRNA)(Kamthanet al., 2015).One of the short non-coding RNAs, siRNAs are usually 21–25 bp long and are ingested by the cell exogenously through viruses or transposons. Another kind of short non-coding RNA is microRNA (miRNA), which is primarily produced endogenously from the nucleus and has an average length of 22 nucleotides. By targeting mRNA at the post-transcriptional stage and causing cleavage or translational inhibition, RNA interference controls the expression of genes (Mandal et al., 2021).
ISBN : 978-81-973154-8-0
