eChapters

The chemical composition of seeds is basically determined by genetic factors and varies among different species and seed parts (Table 1). However, it is influenced by environmental and cultural practices.

1. SEED MATURITY

Harvesting should be done after the attainment of physiological maturity, when the seeds reached complete maturity to avoid harvesting of immature and ill-filled seeds.

1.1. Physiological maturity

It is the stage of accumulation of maximum drymatter within the seeds. It is expressed by maximum seed weight, germination and vigour potential. The moisture content of the seed at this stage is around 25-30% depending up on the species.

1.2. Harvestable maturity

The physiological maturity is represented to a seed and this maturity will not be the same for all the seeds of a single plant / population, due to continuous differential flowering habit. Hence, the stage of attainment of physiological maturity by 80% of the population is considered as the harvestable maturity stage. The moisture content of the seed will be lesser than the physiological maturity stage (18-20%).

1. DEFINITION

Artificial seed technology involves the production of tissue culture derived somatic embryos encased in a protective coating. Artificial seeds have also been often referred to as synthetic seeds. However, the term ‘synthetic seed’ should not be confused with commercial seeds of a synthetic cultivar which is defined as an advanced generation of an open pollinated population composed of a group of selected inbred clones or hybrids. The concept of artificial or synthetic seed is shown in Figure 1.

1. APOMIXIS

Development of seed without fertilization. When the seed formation occurs without sexual fusion, the process is known as apomixis. This occurs by several mechanism, however all apomitic seed have genetic material only from the female plant Apomixis may or may not require pollination and pollen tube germination to initiate seed formation, however sexual union.

1. OVULE DEVELOPMENT

The development of ovule occurs within the ovary, which provides a location for nurture and development of the female gametophyte, its sexual fusion with in the male gametophyte, and embryo development, survival, and eventual regrowth (Fig. 1). Ovule growth begins as a small outgrowth within the nucellus. As megasporogenesis and megagametogenesis continue, the region of the nucellus that is to become the ovule enlarges and differentiates into definite morphological characteristics. Secondary outgrowths, or collars (integuments), soon appear around the periphery of the nucellar outgrowths and envelop it. These usually consist of the inner and outer integuments and ultimately become the testa (seed coat) of the mature ovule.

1. VEGETATIVE PROPAGULE

Vegetative propagation or asexual propagation is the method of propagating plants with the use of organs other than the seed and spore. In contrast to sexual propagation, the union of the male and female sexual gametes (fertilization) is not a requisite to the production of new plants. Hence the word “asexual”, which means “without sex” or “not sexual”.

1. SEED

A seed is defined as a ‘mature ovule’ or a reproductive unit formed from fertilized ovule, consisting of an embryo, reserve food and a protective cover.

Seed is the basic input in agriculture upon which other inputs are applied. A good vigorous seed utilities all the resources and realized as a reasonable output to the grower. It is wealth to the farmer, it is the yesterday’s harvest and tomorrow’s hope. Good seed in good soil realize good yield.

Seeds exhibit a great range of variation in shape, size, colour and behaviour. The most essential factor for the success of plantation is the ready availability of quality seeds. The quality of seed is totally responsible for the future return / performance of each and every seedling.

1. FRUITS

Fruit is a part of a flowering plant that derives from specific tissues of the flower, mainly one or more ovaries.

1.1. Types

1.1.1. Fleshy

1.1.1.1. Simple fleshy fruits

Develop from a flower with a single pistil.

1. FLOWERING

The flowering goes through a phase of vegetative growth producing more stems and leaves and a flowering phase where they produce the organs for sexual reproduction.

1.1. Synchronisation in flowering

Synchronous flowering refers to the phenomenon of coincident, simultaneous flowering of all population of a given species in a large region.

1. INFLORESCENCE

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches.

1.1. Types of inflorescence

Inflorescences can be simple or compound.

1.1.1. Simple inflorescence

Inflorescence of sessile disc florets forming the capitulum

1.1.1.1. Indeterminate

Indeterminate simple inflorescences are generally called racemose. The main kind of racemose inflorescence is the raceme. The other kind of racemose inflorescences can all be derived from this one by dilation, compression, swelling or reduction of the different axes. Some passage forms between the obvious ones are commonly admitted.

Among abiotic stresses, low and high temperature stress is very critical for determining the agricultural production. Plants exhibit a maximum rate of growth and development at an optimum temperature or over a diurnal range of temperatures (Fitter and Hay, 1981). When ambient temperature deviates from optimal, physiological, biochemical, metabolic and molecular changes occur within plants. This is an effort of plants to maximize growth and developmental processes and to maintain cellular homeostasis during such adverse conditions. Under increasingly stressful conditions, plants experience progressively more abnormal, impaired or dysfunctional cellular and whole-plant processes until the cardinal temperatures for survival are reached (Fitter and Hay, 1981). At the extremes of the natural temperature range of a plant, the degree of physiological, cellular, metabolic and molecular dysfunction becomes so severe that it leads to death.

Growth constraints and stress result in significant crop losses and therefore the mechanisms underlying endurance and adaptation to these changes have long been the focus of intense research (Bray 2004). Kültz (2005) elaborated two types of responses to a particular kind of stress:

Vegetable crops, known as protective foods, are important for the healthy diet providing vitamins, minerals, fibre, amino acids and other bioactive compounds. Improvement in vegetable crops is inevitable for better yield, pest or disease resistance, morphological characters, nutritive quality, to adapt with environmental stress, climate change, offseason production, satisfying varying consumer preference etc. Vegetable crops comprise of a large number of species and are rich in diversity. Diverse genetic resources are pre-requisite for any crop improvement programme and vegetable improvement is carried out using exotic introductions, indigenous collection and hybrids/varieties by different breeding systems. Characterisation of genotypes is the description of germplasm giving information on heritable characters so that promising one can be utilised in breeding programme which is the best option for higher yield and other qualities. The morphological, physiological and molecular (biochemical and DNA) traits are called qualitative descriptor and yield, pest/disease resistance, stress tolerance etc are quantitative descriptors that are easily influenced by the environment factors. Apart from the higher production and resistance to biotic and abiotic factors, nutritional traits, flavour, processing qualities that increase the food value is also important in improvement programme of fruits as well as vegetables.

Genetic resources of vegetables available at international and national levels are characterised, evaluated and conserved. With the high diversity of vegetable crops, characterisation and evaluation of genetic resources become a stupendous responsibility requiring extensive infrastructure facilities and varying methods of evaluation (Srivastva, 2012). Genetic resources are characterised on highly heritable traits expressed across the environment. Apart from morphological characterisation, biochemical and molecular characterisation is also conducted that are useful for the identification of biotic and abiotic stress parameters, nutritional and processing quality. Genotype characterisation can be done efficiently using potential of biochemical and molecular markers that help to set up the breeding programme.

Genetic diversity is one of the fundamental character present in any population or species. It is the total variation either phenotypic or genotypic which have occured in a population through due course of evolution. Variation in any species depends on mutation, substitution (insertion/deletion) and response to selection. However, comprehensive studies on theoretical and empirical perspectives for diversity analysis may be found by evolutionary biologists to understand the factor that influences levels of genetic diversity in natural population (Lewontin, 1974). In brief, nucleotides/ protein codes are the basic unit to quantify total amount of variation. Bioinformatic tools and techniques help us to measure inferring relationships between genes, proteins or organisms through use of these DNA/protein sequences by integration of mathematical algorithms, statistical and computer databases.

Diversity analysis is popularly known as phylogenetic analysis in bioinformatic terms. The basic principle of phylogeny is analysis/alignment of characters; whether it is morphological or molecular data. For instance, in case of morphological data of a crop species, the leaf colour/stem colour/fruit colour/grain size etc. may be compared however sequence data is problem of interest for molecular phylogeny. The evolutionary history of any crop species/ organisms inferred from phylogeny analysis mostly depicted through treelike diagrams/ dendrograms. In this chapter, phylogenetic analysis based on only nucleotide/protein sequences are discussed. For analysis of phylogenetics, default assumptions (Baxevanis and Ouellette, 2006) are:

INTRODUCTION

Genetic engineering (GE) and genetically modified organisms (GMOs) provide powerful tools for sustainable development in agriculture, healthcare and many other industries. GMOs are those which were genetically engineered in a laboratory by incorporating a small foreign DNA fragment carrying a gene of interest into the native DNA of the organism. The foreign gene is attached with the necessary regulatory elements to help its expression in the new genetic environment. Genetically modified (GM) crops currently account for some 16 percent of the world’s land planted with soybean, maize, cotton and canola. The global demand for food is increasing because of the growing world population and decreasing arable land. At the same time food and agricultural systems have to respond to several changes such as increasing international competition, globalization and rising consumer demands for improved food quality, safety, health enhancement and convenience. Modern biotechnology involving the use of rDNA technology/genetic engineering has emerged as a powerful tool with many potential application for improving the quantity and quality of food supply. Foods derived from genetically modified crops, commonly referred to as genetically modified food and food ingredients have already become available worldwide with aim of enhancing productivity, decreasing the use of certain agricultural chemicals, modifying the inherent properties of crops, improving the nutritional value or even increasing shelf life. Results of DNA modification may not be limited only to the particular characteristics of the replaced gene. It is therefore important to ensure that when these organisms are released into nature they do not harm the environment or human health [EFSA, 2006]. Such concerns have led to broader interests in the theme of risk assessment in the release of GMOs. A cautious approach is necessary to assess environmental risks which may occur due to introduction of recombinant organisms in the natural environment [Johnson et al., 2007].

Intellectual property: It can be defined as creations of intellectual brain which has value, utility/application in the society and can be traded in commerce for economic benefits.

Significance of Intellectual Property: The significance of protection of Intellectual Property has been realized for wealth and value creation in a knowledge-based economy. The agricultural scientists are comparatively little aware of IPR issues because their primary mandate has always been the free delivery of technology to the end users particularly the farmers. After the implementation of TRIPS Agreement during 1995, the worldwide focus of scientists and planners was shifted on the development of time appropriate technologies, protection of inventions/ technologies and real time technology transfer through licensing for industrial and agricultural growth leading to overall economic development. Under the changing scenario of global trade, where national governments are entering into bilateral agreements for tackling IPR issues to promote trade, agricultural scientists must also look for managing their intellectual properties in tune with the existing IP legislation of the country.

The Indian centre of origin and diversity of cultivated plants represent an outstandingly rich reservoir of nature’s wealth of plant species which include a large number of economically important species including Vegetable Crops. Common vegetables like okra and brinjal are native to this region. Out of the recorded 110 genera and 640 species of cucurbits, 100 species representing 36 genera occur in India. Twenty of these species are endemic. Adoption of high yielding crop varieties and hybrids along with changing land use patterns have led to rapid replacement of native cultivars in most cases. Conserving and sustainable utilization of locally adapted types and primitive landraces are, hence, now major concerns at the national and global levels.

The National Bureau of Plant Genetic Resources (NBPGR) at New Delhi is the nodal organization in India with the national mandate to plan, conduct, promote and coordinate all activities concerning plant exploration and collection, germ plasm import and exchange, plant quarantine, germplasm multiplication and distribution, evaluation and characterization, documentation and conservation of both indigenous and introduced genetic variability in cultivated plants and their wild relatives.

The challenging job of collecting, genetic evaluation and utilization of plant genetic resources cannot be satisfactorily accomplished by one organization. The enormous task of safeguarding and promoting greater utilization of these valuable resources can be best achieved through a networking approach. Professional development is the key to success of this endeavour. NBPGR organizes regularly short-term training courses on various aspects of PGR to impart latest knowledge and techniques to scientists and technicians engaged in crop improvement programmes and handling germpalsm collections.

PLANT EXPLORATION AND GERMPLASM COLLECTION OF PLANT GENETIC RESOURCES

Plant exploration and collection activities have been undertaken for a wide range of needs - by naturalists, travelers and plant hunters over the past several centuries in the quest for new and better economic plants in the southeast Asian region, ornamentals in the Himalayas and many others; by taxonomists for working out plant diversity and delineating phyto- geographic differences, and providing a basis for pinpointing areas with high species diversity and changes over time; world-wide collection, augmentation and characterization of crop plant diversity by Vavilov and co-workers (1926) for understanding the patterns of crop plant diversity and delineating centres of diversity; search for wild forms of species, and wild relatives of crop plants for working out primary centres of origin and crop genepools; biosystematic study, survey and in situ study and collection in protected areas for determining patterns of diversity build-up in crop and wild species. Concept of centres of origin of crop plants, importance of the wild genepool of crops, dependence on wild plants as a source of edible and otherwise useful species ensuing from these efforts provide the basis for systematic exploration and collection of plant genetic resources.

Plant genetic resources represent both the basis for agricultural development and a reservoir of genetic adaptability that acts as a buffer against environmental changes. The erosion of these resources threatens world food security. From an agricultural utilitarian standpoint, plant genetic resources can be considered limited and perishable natural resources. PGR forms a distinct group and include all plant species, which contribute to people livelihoods by providing food, medicine, feed for domestic animals, fibres, clothing, shelter, energy and other uses and are subject to cultivation by man as well as the wild relatives of these species. Genetic diversity simply means all the variety of genes that exist in a particular variety or species. They provide the raw material (genes) which, when used and combined in the right way, produce new and better plant varieties, and are an irreplaceable source of such characteristics as resistance to disease, local adaptation, and productivity. Plant genetic resources are now, and will continue to be in the future, of inestimable value independently of whether scientists use them by means of conventional plant breeding or modern genetic engineering. These genes are dispersed throughout local cultivars and natural plant populations that have been selected over thousands of years by farmers and nature for their characteristics of adaptation, resistance and/or productivity. The road to a continuous increase in the production and quality of food lies through the protection and efficient utilization of plant genetic resources; this requires their conservation, evaluation, documentation and exchange.

Plant biodiversity is the single greatest resource that man garnered from nature during the long cultural development phase. More than 2.5 lakh species of mosses, ferns, conifers and flowering plants and more than 50,000 plant species are yet to be documented, primarily in the remote and less studied reaches of tropical forests.

Vegetable crops in which rich diversity occurs in India are Cowpea, Common bean, Cole crops, Okra, Brinjal, Sweet potato, Taros, Yams, Sword bean, Velvet bean and Elephant foot yam. Wide diversity was observed in chives, leeks and other Allium spp in Kumaoun and Garhwal Himalayas; cluster bean in Western arid zone; lab lab bean in Deccan plateau; cucurbits in Rajasthan and Madhya Pradesh and leaf vegetables like Amaranth and Fagopyrum in Western Himalayan region. Tropical vegetables consist of solanaceus fruits (tomato, hot pepper, brinjal), cucurbits (water melon, muskmelon, cucumber, pumpkins and squashes, bottle gourd, chow-chow, ivy gourd, bitter gourd, ash gourd, round gourd, snake gourd, pointed gourd, sponge gourd, ridge gourd), malvaceous vegetables (Okra),legumes (common bean, lima bean, dolichos bean, cowpea, sword bean, winged bean), allium (onion, shallot, garlic, leek) and leaf vegetables (amaranth, spinach beet, Ceylon spinach). The indigenous vegetables both cultivated and wild have important role in household nutrition, economy and food security. There are 25 hot spots of biodiversity of which Western Ghats and Eastern Himalayan region are the most important ones. Indo-Myanmar region is one of the largest hot spots of the world and is the centre of origin of tuber crops like yams, taro, Amorphophallus and Alocasia. Tropical tuber crops form an important group of subsistence crops especially to those living in tropics and sub tropical zones. Tuber crops are the third important food crops after cereals and grain legumes. Major tuber crops are cassava, sweet potato, Asiatic yam, African yam, lesser yam, elephant foot yam, taro, tannia and country potato. Minor tuber crops are arrowroot, winged bean, yam bean, canna, safed musli and Jerusalem artichoke. Sweet potato is one of the world’s highest yielding crops.

Biodiversity is the origin of all species of crops and domesticated and the variety within them. It is also the foundation of ecosystem services essential to sustain agriculture and human well-being. Today’s crop and livestock biodiversity are the result of many thousands years of human intervention. The biodiversity in vegetable crops is composed by the genetic diversity, as species diversity (inter specific diversity) and as diversity of genes within a species (intra specific diversity) referring to the vegetable grown varieties, and by the diversity of agro-ecosystems (agro-biodiversity).

Crop diversity is the variance in genetic and phenotypic characteristics of plants used in agriculture. Over the past 50 years, there has been a major decline in two components of crop diversity; genetic diversity within each crop and the number of species commonly grown.

3.1 Tomato

Tomato (Lycopersicon esculentum) is an important vegetable crop. Its 2n= 24.

Floral biology

Flowers are borne in small forked racemose cyme. Anthesis starts at 6.30 a.m. and continues up to 11.00 a.m. Anther dehiscence is longitudinal. It occurs 1-2 days after opening of corolla. The stamen sheds its pollen when the style grows up through anther tube, thus self-pollination occurs. When the stigma protrudes above the anther tube, chances of cross pollination through bees increases. The optimum temperature for pollination is around 21°C.