eChapters

6.1 Introduction

Water deficit stress is a serious and frequently encountered abiotic stress in the terrestrial surface. Its deleterious effects on plant growth and productivity are well documented. Plant responses to water stress are believed to be complex as these operate at various levels of plant organization. Several in built physiological and biochemical mechanisms provide resistance to plants against stress. An understanding of the processes linked to these mechanisms is vital for optimizing crop growth and productivity under stress. Plants respond and adapt to water stress by altering cellular metabolism, thus invoking stress tolerance. Alteration in endogenous concentrations of growth regulators along with accumulation of osmolytes, modifications in antioxidant cascade, changes in protein profiles and induction of gene expression in plants under stress are important characteristic metabolic changes that invoke stress tolerance at the cellular level. Alteration in endogenous concentrations of plant bio-regulators under stress helps plants through better turgor maintenance and efficient water usage by influencing stomatal functioning, hydraulic conductivity and morphological adaptation. Progress made in plant adaptation to water stress is an outcome of advances made in analytical techniques on endogenous growth regulator analysis and powerful and reliable molecular and genetic techniques.

2.1 Introduction

Dear students, you shall be taught plant biotechnology during the third semester in the course ‘Elementary Plant Biotechnology’. But, for understanding of non-conventional breeding methods/techniques you should acquire some knowledge of basic plant biotechnology. Hence, in this chapter plant biotechnology is introduced to you in brief.

2.2 Definition

The term ‘biotechnology’ stems from fusion of ‘biology’ and ‘technology’. It was coined by Karl Ereky, a Hungarian agricultural engineer, in the beginning of 20th century. According to him, all processes used to yield finished products from raw materials with the help of living organism come under biotechnology. It may be defined in number of ways. However, in simple terms, biotechnology may be defined as ‘the controlled use of biological agents, such as microorganisms, or cellular components, for beneficial use’ (U.S. National Science Foundation).

Development of Plant Body

A vascular plant begins in existence as a morphologically simple unicellular zygote (2n). The zygote develops into the embryo which in the long run develops into the mature sporophyte. The development of the sporophyte (2n) involves division and differentiation of cells and organization of cells into the tissue systems. The embryo of the seed plant possesses relatively simple structure as compared to the mature sporophyte. The embryo bears a limited number of parts containing generally only axis bearing one or more cotyledons. The cells and the tissues of this structure are less differentiated. However, the embryo grows further, because of the presence of the meristems, at two opposite ends of the axis, of future shoot and root. After germination of the seed during development of the shoot and root new apical meristems appear which cause a vegetative growth and reproductive stage of the plant attained.

Fundamental Parts of the Plant Body

The plant body consists of a number of organ i.e., root, stem, leaf and flower. Each part has different functions for plant growth.Flower consists of sepal, petals, stamens, carpels and sometimes also sterile members. Each organ is made up of number of tissue systems; each tissue system consists of number of tissues. Tissue consists of group of cells that are alike in origin, structure and function.

Abstract

The establishment of All-India Coordinated Wheat Improvement Project in 1965 coincided with the introduction of high yielding semi-dwarf wheat varieties. Since then India has made very impressive progress in increasing wheat production over the past three and half decades. India now ranks as the second largest wheat-producing nation in the world. In fact from a state of “Ship to mouth” in 30 years or so India has become a nation of surpluses. The significant contribution made by the project in helping the increased wheat production cannot be ignored. Through coordinated research and development, nearly 200 wheat varieties have been developed during the last 35 years in India. However, only a small number of them produced without backing of specific quality breeding programs excel in quality traits also. The increasing demand of baked and pasta products in the country along with economic liberalization and global trade have offered opportunities for better utilization of the surplus wheat. Thus, in the current decade and beyond, wheat quality needs uppermost attention to meet the trade requirements for domestic and export purposes. Therefore, there is a need to reorient the wheat improvement programs in the country.

Definition

Based on various standard sources, plant breeding has been defined in various ways. A few important and standard definitions are:

The art and science of changing plants genetically.

Plant breeding is the genetic adjustment of plants to the service of man.

Improvement of crop plants as the result of process of evolution directed by man for his own ends. The basic principles of plant breeding are thus the principles of evolution. Directed evolution as imposed in plant breeding differs from natural evolution chiefly in a greatly reduced time-scale, and in a more precise control over the factors which govern hybridization and selection.

The science and art of manipulating the heredity of plants for a specific purpose.

Plant breeding is a deliberate effort by human to nudge nature, with respect to the heredity of plants, to an advantage. The changes made in plants are permanent and heritable and the professionals who carry out this task are called plant breeders. This effort at adjusting the status quo is instigated by a desire of humans to improve certain aspects of plants to perform new roles or enhance existing ones. As a result, the term “plant breeding” is often used synonymously with “plant improvement” in recent years. Normally the term plant breeding connotes the involvement of sexual process in effecting a desired change; however, it is also true that modern plant breeding also includes the manipulation of asexually reproducing plants (plants that do not reproduce through the sexual process). Breeding is therefore about manipulating plant attributes, structure, and composition, to make them more useful to humans.

Gepts and Hanock (2006) have defined plant breeding as an applied, multidisciplinary science. It is the application of genetic principles and practices associated with the development of cultivars more suited to the needs of human than the ability to survive in the wild; it uses knowledge from agronomy, botany, genetics, physiology, pathology, entomology, biochemistry and statistics. Of particular importance is the ability to transfer, in addition to major genes, large suites of genes conditioning quantitative traits such as productivity and other traits of interest to humans. The ultimate outcome of plant breeding is mainly improved cultivars. Therefore, plant breeding is primarily an organismal science even though it is eminently suited to translate information at molecular level (DNA sequences, protein products) into economically important phenotypes. The traditional definition of plant breeding includes only those scientists who develop new cultivars and improved germplasm, however, many feel this definition should be expanded to include scientists who contribute to crop improvement through breeding research.

Introduction
Plant breeding and genetics are at the forefront of agricultural innovation, playing a crucial role in enhancing crop traits to meet the ever-growing demands for food, fiber, and fuel. This chapter delves into the scientific principles, methods, and modern advancements in plant breeding and genetics, providing a comprehensive understanding of how these disciplines contribute to global food security and environmental sustainability. The chapter begins by exploring the fundamental principles of plant breeding, including heredity, genetic variation, selection, and hybridization. These concepts form the foundation for developing new plant varieties that exhibit desirable traits such as improved yield, disease resistance, and environmental adaptability. The importance of genetic variation is emphasized as a key driver of plant improvement, with discussions on the sources of genetic variation, the role of germplasm resources, and the impact of genetic diversity on plant adaptation. As the chapter progresses, various breeding techniques and strategies are examined, including mass selection, pedigree breeding, backcrossing, and markerassisted breeding. These methods are crucial for developing new plant varieties that can withstand the challenges posed by climate change, pests, and diseases. The chapter also addresses the role of genomics in plant breeding, highlighting the significance of genomic selection, gene editing, and bioinformatics in accelerating the breeding process and enhancing crop traits. The chapter further explores the controversial topic of genetically modified organisms (GMOs), discussing the principles of genetic engineering, the rise of genetically modified crops, and the associated controversies and concerns. The importance of GMOs in addressing global food security and environmental challenges is also discussed, providing a balanced perspective on their potential benefits and risks. The chapter concludes by emphasizing the critical role of plant breeding and genetics in ensuring food security and combating global warming. By developing climate-resilient crop varieties, improving water efficiency, and enhancing disease and pest resistance, plant breeding and genetics can contribute to sustainable agricultural practices that reduce greenhouse gas emissions and conserve natural resources

1. Mendel presented his results in the form of

   a) Two paper in French langua

   b) Two paper in German language

   c) One paper in German language

   d) None of the above

2. The alternative forms of a gene are called

   a) Allelomorph

   b) Gene

   c) Alleles

   d) None of these

Plant breeding is the art and science of changing and improving the heredity of plants. The art of plant breeding lies in the breeder’s skill in observing and selection of superior plants. The value of selection largely depends upon the skill of the breeder. The skill that a breeder develops though a close and deep study of the concerned crop species. Before the rediscovery of the Mendelian Laws in 1900 AD, the plant breeding is as an art. The modern age of plant breeding began in the early part of the twentieth century, after Mendel’s work was rediscovered. Today plant breeding is a specialized technology based on genetics. It is now clearly understood that within a given environment, crop improvement has to be achieved through superior heredity. Plant breeding developed into a science as knowledge progressed towards the genetics, cytogenetic, physiology, pathology, biochemistry, biotechnology and biometry. The fundamental of plant breeding was based on recognition of the genes. The genes were identified by their effects on the visible expression of plant traits such as whether a plant was a dwarf or tall, or the flower color was white or pink. Through systematic hybridization, a desirable gene could be transferred from one to another cultivar. More recently the science of molecular genetics proposes to advance plant breeding. Molecular genetics was ushered in with the description of chemical structure of deoxy-ribonucleic acid (DNA), the material that constitutes the genes. DNA carries the instructions for synthesis of specific proteins that determine the visible expression of particular characters. The new technology does not supplant nor diminish the importance or need for traditional selection and crossing procedures in the breeding of improved cultivars. The performance of today’s cultivars reached at high levels through refined selection and hybridization breeding procedure.

The early developments in plant breeding that took place are based on archaeological evidence. The first efforts to grow wild plants probably occurred in Southeast Asia culminated in the domestication of some of the many plants with which humans experimented in 13000 BC. By 10000 BC, advanced knowledge existed of such plants as rice (Oryza sativa), several legumes such as pea (Pisum sativum), runner bean or broad bean (Phaseolus or Vicia spp.) and possibly soybean (Glycine max). At this point crops became domesticated.

Although the beginning of civilization in China and Southeast Asia are obscure and fragmented. The number of successful species domesticated indicates considerable success in plant breeding. The third site of independent agricultural development and plant breeding was in south-central Mexico between 6700 and 5000 BC. Squash and avocados were domesticated first and a number of species of maize. Domestication in the Middle East and China included the self-fertilized crop like cereals and soybean.

Systematic scientific efforts to improve genetic potential of crops in India were initiated in 1905 at the Imperial/Indian Agricultural Research Institute. In 1929, with the establishment of the Indian Council of Agricultural Research (ICAR), several associated developments took place in the first half of the 20th century leading to establishment of several crop-based institutes (sugarcane, cotton, jute, rice, oilseeds, tobacco, potato) and multidisciplinary institutes such as the Indian Agricultural Research Institute (IARI), Central Arid Zone Research Institute (CAZRI), and Central Plantation Crops Research Institute (CPCRI). Additionally, a Project on Intensification of Regional Research in Cotton, Oilseeds and Millets (PIRRCOM) was implemented during 1950s with establishment of several research stations in different regions.

Broadly and conceptually breeding methods can be classified into four groups. These are:

• Selection breeding
• Combination breeding
• Hybrid breeding
• Special breeding techniques

There are fluid transitions and similarities between the individual groups of breeding methods. Selection not only takes place in the group termed selection breeding but also in other groups. In breeding varieties by combination, new variation is generated by crossing genetically different parents followed by application of various selection methods and ultimately development of a new recombinant type pure-line. In hybrid breeding, inbred lines of different genetic constitution are produced by selfing, pair crossing and other methods and from these best lines are selected and new hybrids are developed. In addition, breeding methods can also be classified according to other criteria. For example, breeding methods have also been classified according to the manner of propagation of the varieties. These are:

Crop improvement

Crop improvement refers to the genetic alteration of plants to satisfy human needs. It deals with the improvement of crops and production of new crop varieties, which are far superior to existing types in all characters. In pre-history, our ancestors in various parts of the world brought into cultivation a few hundred species from the hundreds of thousands available. In the process they transformed elements of these species into crops though genetic alterations that involved conscious and unconscious selection, the differential reproduction of variants. Through a long history of trial and error, a relatively few plant species have become the mainstay of agriculture and thus the world’s food supply. This process of domestication involved the identification of certain useful wild species combined with a process of selection that brought about changes in appearance, quality, and productivity.

Definition

Plant breeding can be defined as an art, a science, and technology of improving the genetic makeup of plants in relation to their economic use for the mankind.

OR

Plant breeding is the art and science of improving the heredity of plants for the benefit of mankind.

OR

Plant breeding deals with the genetic improvement of crop plants also known as science of crop improvement.

OR

Science of changing and improving the heredity of plants

The word cell was coined by Robert Hooke with the help of compound microscope. Cell is the basic unit of life. A plant cell has three distinct components a). Cell wall b). Protoplasm and c). Vacuole. Cell wall  and  vacuole are considered as non-living substances. The protoplasm which is living is  composed of 1. Cytoplasm and 2. Nucleus. The cytoplasm contains several organelles such as mitochondria, chloroplast, ribosomes, endoplasmic reticulum, golgi complex, lysosomes, plastids etc.

21.1 Introduction

Plants and insects share a wonderful relationship. Both are dependent on each other at different levels and chemicals emitted by plants connect them to a large extent.  “Plants” contribute to a major share of occupancy on earth and makes several organisms such as insects & microbes and also humans to depend on them for their survival. This dependency leading to several interesting interactions between plants & insects which are often utilized by humans for their own benefit. Plants maintain incredible communication with their associated organisms. Since plants are rich banks of chemicals and constantly emit them in to its immediate environment which contributes in communication between insects and plants. Insects are the major organisms that have a long relation with the plants and there are several incredible ways how plants can interact with insect species.

Plant collection and field preparation of specimens are the fundamental aspects of study, training and research in plant systematics. Herbarium specimens are the permanent records of plant species of a particular place at a given time. Therefore, the plants should be carefully collected, selected, and the herbarium specimens should be properly prepared and preserved.
6.1 Which Type of Specimens Should Be Collected?
The points to be kept in mind during a plant collection are:
1. Collect entire, vigorously growing typical specimens.
2. Select such individuals that represent almost all phases of the natural population.
3. Avoid collecting insect-damaged specimens.
4. Collect underground parts (e.g. roots, bulbs, rhizomes, tubers, etc.) of herbaceous perennials.
5. Collect those specimens of flowering plants that contain flowers, fruits, and seeds, because keys are prepared mainly on the basis of these characters.
6. Specimens larger than the size of a single sheet, should be divided an pressed on a series of sheets.
7. Collect plants with the leaves intact as different kinds of foliage prove helpful in identification.
8. Collect the bark and wood samples of the woody plants.
9. Avoid collecting rare or uncommon plants. Never collect the only plant of a species at a locality.

· Plants have structural and biochemical defense mechanisms against pathogens.

· Structural defense mechanisms can be pre-existing (e.g. wax, thick cuticle) or post-infectional (e.g. cork layer formation, tyloses).

· Pre-existing biochemical defenses include inhibitors and phenolics; post infectional defenses include phytoalexins and plantibodies.

· Disease development depends on a successful host-pathogen interaction; defense mechanisms are ineffective during a compatible reaction.

Summary

This review addresses various defense strategies evolved by plants to resist pathogen attack.Of the different defensive strategies, pathogen attack either induces or enhances constitutively the synthesis of a spectrum of diverse chemical compounds in various plant species. These chemical compounds also called secondary metabolites are classified broadly as nitrogen compounds, terpenoids and phenolics and have been documented to possess broad range antifungal, antimicrobial and pesticidal activities. Such defensive compounds could be extracted and developed as eco-friendly biopesticides/microbicides because of their natural occurrence, ephemeral nature and biodegradability. These will be favorable alternative strategies compared to chemical pesticides that are fraught with various harmful side effects.