eChapters

1. DEFINITION

Sum of those properties of seed, which determine the potential level of activity and performance of the seed or seed lot during germination and seedling emergence. i.e., rapid and uniform production of healthy seedling and stand establishment under a wide range of field conditions is considered as seed vigour.

In a vigour test, the seed is introduced to a stressful environment unfavorable to seedling development. This environment can be cool, cold or warm, or a combination of either high humidity and high temperatures, or heavy moisture at low temperatures. A vigor test cannot replace a germination test, but rather supplements it with more information about seed quality.

1. FIELD OF APPLICABILITY

Grow-out test is the official measure for controlling the genetic purity of the seed lot. It serves as ‘pre-control’ as well as a ‘post control’ test for avoiding genetic contaminations. According to the official regulations in India, it is prerequisite for seed certification of hybrids of certain species such as cotton, castor, musk melon and brinjal.

The test is conducted for checking the sellers label with respect to genetic purity status of the seed lot under the provisions of the Seeds Act 1966. In addition, grow-out test can also be used as a measure to judge the efficacy of the certification agency or the inspector.

The relative long periods of time required for completion of germination tests delays the seed marketing. This necessiated the development of rapid methods for estimating the germination capacity of seeds. This test was developed by Lakon (1942) in Germany.

1. PRINCIPLE

It is a biochemical test, in which living cells are made visible by reduction of an indicator dye. The indicator used is 2,3,5 triphenyl tetrazolium chloride. Within the seed tissues, it interferes with the reduction processes of living cells and accepts hydrogen from the hydrogenases. By hydrogenation of the 2,3,5-triphenyl tetrazolium chloride, a red stable and non diffusible substance, triphenyl formazan is produced in living cells (Fig. 1).

1. GERMINATION TEST PROCEDURES

Although several methods are available for germination testing it is suggested that use one of the two major methods described here because these are adaptable to most environments and in general give uniform results Select 400 seeds randomly and used for germination in 4 replications.

1.1. Top of Paper (TP)

Seeds are placed on one or more layers of moist filter paper or blotter paper in petriplates These petriplates are covered with lid and placed inside the gemination cabinet This is suitable for those seeds which required light Cut the paper to the size and shape of the dishes (Fig. 1).

Place a layer of paper in each dish If the paper is too thin use a double layer Label the top and bottom of each dish with the accession number number of the replicates and date of the test Moisten the paper with water (Fig. 2)

1. SEED MOISTURE

Seed moisture is one of the most important deciding factors of seed viability and quality during storage. Hence, determination of seed moisture content and drying to the safe moisture content is utmost important before transit and storage.

According to ISTA (1985), moisture content of the sample is defined as that loss of weight when it is dried in accordance with the rules or the amount of water collected when it is distilled. It is expressed as percentage of the original weight of sample (wet basis).

1.1. Principle

Moisture present in the seed is removed completely as much as possible without oxidation or decomposition or loss in other volatile substances by applying heat. The weight loss due to drying is estimated and the moisture content is calculated.

1. SEED PURITY AND ITS COMPONENTS

Seed purity analysis from the working sample taken from submitted sample is made in accordance to ISTA rules. The uncertified seed sample is generally a mixture of pure seeds, inert matter and biological impurities including genetically impure seeds of the variety.

A buyer expects to have good seed and not a mixture of pure seed with a high percentage of chaff, straw, sand, weed seeds and other crop seeds and also genetically impure or mixed seeds.

Purity analysis is a test to estimate the extent of biotic and abiotic impurities present in the seed lot of a variety.

1. MIXING AND DIVIDING

The main objective of mixing and dividing of seeds is to obtain the representative homogenous seed sample for analysis by reducing the submitted sample to the desired size of working sample.

2. TYPES OF MECHANICAL DIVIDERS

2.1. Boerner divider

The principle involved in mixing and dividing in gravitational force. It consists of a hopper, a cone and series of baffles directing the seeds into 2 spouts. The baffles are of equal size and equally spaced and every alternate one leading to one spout. They are arranged in circle and are directed inward. A valve at the base of the hopper retains the seeds in the hopper. When the valve is opened, the seeds fall by gravity over the cone where it is equally distributed and approximately equal quantity of seeds will be collected in each spout. A disadvantage of this divider is that it is difficult to check for cleanliness (Fig. 1).

1. SEED LOT

A specified quantity of seed which is physically identifiable to the types of which certificates may be issued.

2. SAMPLING

A sample is obtained from the seed lot by taking small portions at random from different position of the lot and combining them. It is a representative sample of a seed lot.

The objective of sampling is to obtain a representative sample of a size suitable for test. When the sample originates from seed lot, it is expected that the results reflect the average quality of the seed lot.

1. MINIMUM SEED CERTIFICATION STANDARDS

In a seed quality control programme through seed certification, the minimum seed certification standards, in fact, are the minimum standard conditions which must be met. The minimum seed certification standards, thus are the standards required for the certification of seeds by the certification agencies.

The minimum seed certification standards can be broadly grouped into two groups.

1. PRESENCE OF OBJECTIONABLE WEEDS

Objectionable weeds present in the seed crop of the respective species should be removed and destroyed before flowering. They should be verified during field inspection (Table 1). The maximum permitted limit of objectionable weed in seed crop is presented in table 2.

1. UNIT OF CERTIFICATION

The entire area planted under seed production programme by an individual constitutes an unit, provided;

1. All the seed production programme is to produce seed of one category and one variety.
2. Area does not exceed 10 hectares and scattered fields constituting one unit (10 ha) should not be separated by more than 50 metres distance (Table 1).
3. The crop of the entire area is more or less of the same growth stage. The seed crop is grown as sole crop and it is not heavily and uniformly lodged.

1. SEED CERTIFICATION

Seed Certification is a legally sanctioned system for quality control on seed multiplication and production. It involves field inspection, pre and post control tests and seed quality tests.

1.1. Phases of Seed Certification

Certification shall be completed in six broad phases listed under

Any new variety produced by the Scientist has to be multiplied to many times to meet the needs of the farmers. In order to ensure the availability of quality seeds, Government of India have enacted Seed Act 1966 and Seed Rules, 1968. The Seed (Control) order 1983 was promulgated under essential commodities act, 1955 in order to ensure the production, marketing and distribution of the seeds.

1. SEED ACT 1966

The objective of Seed Act is for regulating the quality of certain notified kind / varieties of seeds for sale and for matters connected therewith. The Seed Act passed by the Indian Parliament in 1966 was designed to create a ‘climate’ in which the seeds man could operate effectively and to make good quality seed available to cultivators. Seed Rules under the Act were notified in September 1968 and the act was implemented in October 1969. This act extent to the whole of India and it has 25 sections.

1. SEED FORTIFICATION

It is process of enriching the seeds with bioactive chemicals for improving the germination and seedling vigour. To the known volume of seeds, one third volume of the nutrient solution is added and allowed to imbibe for short duration. The imbibed seeds should be dried under shade. The fortification treatments recommended for different crops are depicted

1. INTRODUCTION

Field run seeds obtained from the seed production field posses high moisture and physical contaminants like trash and other inert materials (sand, stones, soil etc.,), diseased and pest damaged seeds, other crop seeds, weed seeds, deteriorated and damaged seeds, off-size and ill filled seeds, plant remnants etc. Seed processing is must to dry the seeds to safe moisture level, remove unwanted and inert materials as detailed above.

Seed qualities such as vigour and viability are improved by certain physical characteristics of the seed i.e., shape, size, large, denser and sound seed, etc. So, if grading is done to obtain a particular range of size, shape, length and density of the seeds, the quality of the lot is upgraded.

Seed processing refers to all the steps necessary for preparation of harvested seed for marketing namely handling, drying, shelling, preconditioning, cleaning, size grading, treating and packaging.

1. SEED PROCESSING

1.1. Purpose

Seed processing is necessary in order to dry the seeds to safe moisture level, remove or reduce to the extent possible the various undesirable materials, weed seeds, other crop seeds, deteriorated or damaged seeds, uniform size grading and seed treatment to upgrade the overall seed quality.

1.2. Physical characteristics that aid in grading and upgrading

The threshed produce are pre-cleaned either manually or mechanically and are graded using different, but optimum sieves of specified sizes. This grading bring homogeneity in the lot which aids in obtaining uniformity among the population in the subsequent sowing.

Different kinds of seeds can be separated when they differ in one or more physical characteristics. Physical characteristics normally used to separate seeds are size shape, length, weight, colour, surface texture, affinity to liquids, electrical conductivity, etc.

1. SEED DRYING

The process of elimination of moisture from the seed is called drying.

2. STAGE OF MOISTURE ELIMINATION

The moisture from the seed is eliminated in 2 stages

1. Surface moisture of the seed that initially removed by the drying air.
2. The removal of the moisture in the surface cause an imbalance in the moisture potential in the surface of the seed and the inner portion of the seed which leads to the migration of moisture from the inner organ to the surface.

The migration of moisture to the surface is slower than the evaporation and a moisture gradient is developed in the kernel. Elimination of moisture from the seed depends upon the relative humidity and temperature of the environment surrounding the seed.

1. SEED EXTRACTION

The processing of seeds starts from the extraction of seed material from the plant parts. The seed removal in dry fruits is known as threshing, while that of wet fruits is known as extraction.

2. METHODS OF SEED EXTRACTION

2.1. Dry extraction

Dry extraction is done either manually or mechanically. Manual extraction is by beating with pliable bamboo stick or by beating against a hard surface. Threshers are used for mechanical extraction. In this, care should be taken to avoid mechanical injury. Eg. All agricultural crops.

2. METHODS OF HARVEST

The seed can be harvested either manually or mechanically. In mechanical harvesting, single harvest is possible, but care should be taken to avoid mechanical injury. In manual harvesting, crops can be harvested either as single harvest or as periodical harvest. The crops having continuous flowering habit are to be harvested in different harvests/ pickings.

2.1. Manual harvesting

Harvesting any crop can be done manually. Manual harvesting is done by the hand of harvest worker. Multipicking in pulses and vegetables is done by manual methods.

1. INTRODUCTION

Green Revolution Technologies (GRT) such as greater use of synthetic agrochemicals like fertilizers and pesticides, adoption of nutrient responsive high yielding varieties, greater exploitation of irrigation potentials etc. have boosted the production output in most cases. However, continuous use of these high energy inputs indiscriminately now leads to decline in production and productivity of various crops as well as deterioration of soil health and environment. The most unfortunate impacts of GRT on Indian Agriculture are imbalance in production, dependency on synthetic chemical fertilizers, increase in secondary and micronutrient deficiencies, increase in pesticide use, unscientific water management and distribution, reduction in productivity, reduction in quality of the produce, extinction of gene pool, environmental pollution and imbalance in social and economic status.

Moreover, today the rural economy is now facing a challenge of over dependence on outside inputs and day-by-day increase in price of these inputs. Further, Indian Agriculture will face the market competition due to globalization of trade as per World Trade Organization (WTO). Thus, apart from quantity, quality will be the important factor. Such varieties of concern and problems of modern Indian Agriculture gave birth to various new concepts of farming such as organic farming, natural farming, biodynamic agriculture, do-nothing agriculture, eco-farming, etc. Therefore, for sustaining the productivity of the crop, maintaining the soil health and healthy ecosystem, there is a need for adoption of an alternative farming system, may be the organic farming.

Organic farming is not new to Indian farming community. Several forms of organic farming are being successfully practiced in diverse climate, particularly in rainfed, tribal, mountain hills and resource poor areas of the country. It safeguards/improves quality of resources and environment. It is labour intensive and provides an opportunity to increase rural employment.

For a product to be called and labelled “organic”, it should have been produced from start (seed) to end (the produces, the consumer is buying) in an organic way. International Federation of Organic Movement (IFOAM) has clearly laid down the condition that in order to get organic certification to the produces, the seed used for sowing should also have been produced organically. To enter into organic agriculture, timely research has been warranted to study the strategies and efficacies of organic seed production to fulfill the global organic seed demand.

Organic seed production system involves use of organic seed quality enhancement treatments, integrated organic nutrient management practices viz., organic manures, green manures and biofertilizers etc., and integrated organic plant protection viz., agronomic practices, crop rotation, growing border/trap crops and use of botanicals, biopesticides and biocontrol agents apart from encouraging natural parasites, predators and parasitoids etc.

1. DEFINITION

Micropropagation is the growing of plants from meristematic tissue or somatic cells of superior plants on nutrient suitable media under controlled aseptic physical conditions.

1. SELECTION OF SITE

Select a location where one could ensure semi-shady conditions. Well drained medium-loam soil; rich in organic matter and neutral soil pH. An irrigation source in the vicinity with natural pH water is highly desirable.

1. CUT FLOWERS

1.1. Common name, scientific name and family

1. TROPICAL FRUITS

1.1. Common name, botanical name and family

1. FORAGE LEGUMES

1.1. Isolation

1. TECHNIQUES OF HYBRID SEED PRODUCTION

1.1. Field crops

Table 1: Techniques of hybrid seed production in field crops

1. LAND REQUIREMENTS

1. LAND REQUIREMENTS

Land should be fertile with selected irrigation and good drainage facilities. It should be free from volunteer plants. The field should not have been grown with the same crop in the previous season. If grown, it should be the production of same class of seed for the same variety.

1. HAND EMASCULATION AND POLLINATION

The male part of seed parent is removed by hand before anthesis to check the self pollination from the crop plants with bisexual flower having fertile male and female part. This process is known as emasculation. These emasculated flowers are then pollinated by the pollens collected from pollinator parent to produce hybrid seed (Fig. 1). Eg. Cotton, tomato, brinjal.

1. HETEROSIS

1.1. Definition

Heterosis or hybrid vigor or outbreeding enhancement, is the increased function of any biological quality in a hybrid offspring. It is the occurrence of a genetically superior offspring from mixing the genes of its parents.

1.2. Inbreeding depression

Inbreeding depression is the reduced fitness in a given population as a result of breeding of related individuals. In general, the higher the genetic variation within a breeding population, the less likely it is to suffer from inbreeding depression.

1. GENETIC PRINCIPLES

1.1. Maintenance of genetic purity during seed production

The methods suggested by Home (1953) and Hartmann and Kester (1968) may be used wholly or in part to maintain high levels of genetic purity during seed production.

The various steps suggested by Home (1953) to maintain varietal purity are as follows:

1. SEED

It is a matured ovule usually developed after fertilization. Seed can also be defined as the embryonic plant in resting stage, usually supplied with food reserves in the cotyledons or endosperm or in perisperm with the protective structure called seed coat. In a nutshell, it is a dry dispersal unit of a plant. It develops into an individual similar to the one that produced it

1. INTRODUCTION

Seed is the most important determinant of agricultural production potential, on which the efficacy of other agriculture inputs is dependent. Seeds of appropriate characteristics are required to meet the demand of diverse agro-climatic conditions and intensive cropping systems. Sustained increase in agriculture production and productivity is dependent, to a large extent, on development of new and improved varieties of crops and an efficient system for timely supply of quality seeds to farmers..

1. INTRODUCTION

Indian population is estimated to increase to about 1400 million by 2025. Consequently, India’s requirements for food grains and other food products to feed the increasing population will continue to rise. The food grain requirements are estimated at 350 to 370 million tonnes by 2025. The demand pattern for agricultural commodities for the domestic market will also shift as a result of increasing incomes and faster urbanization. Compared to 26% increase in 1991, the urban population is projected to increase by 42% in 2020. For competing in the global market, the product pattern will shift to high value commodities like fruits, vegetables, floriculture, dairy products, meat and marine products. In such a future scenario, it is necessary to increase agricultural production through improved cropping system, judicious use of agro-inputs and wide use of modern agricultural technology. It is also important to augment and streamline the existing marketing system including handling, transportation, storage, processing and distribution.

1. DEFINITION

Seed village definition is to see that the aim right from the start is to make a holistic transformation in the village. Seed village concept is a “Win-Win model”, says Deepak Mullick, one of India’s foremost professionals in agribusiness. It is also known as “Compact area approach”. Seed village area should be suitable for crop or varieties. Seed in compact area, whole village should be involved. The whole farmers in the village cultivate same crop, same variety and follow same cultivation practices.

1. SEED CLASSES

Generation system of seed multiplication is nothing but the production of a particular class of seed from specific class of seed up to certified seed stage. The choice of a proper seed multiplication model is the key to further success of a seed programme, which basically depends upon

1. BASIC NUCLEUS SEED

The seed of the notified variety collected from the evolving institute with all the passport information is considered as basic nucleus seed. This seed is sown in prepared healthy field with more row to row and plant to plant distance than the normal recommendation at required isolation distance. Prescribed dose of fertilizer, irrigation and required plant protection measures are provided.

Off types and diseases plants are rogued out at seedling, before flowering, flowering and at physiological maturity stages. Plants are marked with contrast color thread and observed regularly. Marked plants are harvested separately and its produce is used as source seed for production of nucleus seed for next year. Produce of unmarked plants are used as nucleus seed for production of breeders seed. Harvesting threshing and drying are done without reducing physical and genetic purity. The discolored and diseased seeds are removed. The pure seed obtained is the nucleus seed for seed multiplication chain

Genetic purity (trueness to type) of a variety can deteriorate due to several factors during production cycles. The best means to insure genetic purity therefore, would be to overcome to the greatest possible extent the various factors responsible for genetic deterioration. The important factors of apparent and real deterioration of varieties as listed by Kadam (1942) are as follows:

Developmental variations

Mechanical mixtures

Mutations

Natural crossing

Minor genetic variations

Selective influence of diseases

The technique of the plant breeder

1. VARIETY

Variety is a seed/crop which suit the prevailing agroclimatic conditions, high yielding and possessing desirable attributes such as disease resistance, earliness and grain quality. Similarly, the seed should be pure, appropriate classes, and obtained from an authorised official agency.

1. PLANT DOMESTICATION AND INTRODUCTION

Domestication is the process of bringing wild species under human management. Under domestciation, the crop species have changed considerably as compared to the wild species from which they originated.

1. SEED GERMINATION

The process whereby seeds sprout and begin to grow is known as germination.

Germination is the onset growth of a seed, often following a period of dormancy, in response to suitable environmental conditions. During germination (the growth and development process) of a seed, the water is absorbed through micropyle, and the formerly dormant embryo resumes growth and emerges from the seed.

1. INTRODUCTION

In plants, seed dormancy is controlled by temperature, light and hormones. Unlike animals, which secrete hormones from special glands, hormones are always present in plant cells. Each plant hormone plays multiple roles, depending on the site of action, the life stage of the plant and the hormone’s concentration. A plant hormone is any chemical that is produced in one part of the plant that has a targeted function elsewhere. Certain hormones induce and keep seeds in a dormant state, while others cause seeds to break dormancy and initiate germination They are stored in regions where stimulus are and then released for transport through either phloem or mesophyll when the appropriate stimulus occurs. These are chemical messengers influencing many patterns of plant development

The first theory is that the five classic plant hormones, auxin, cytokinins (CKs), gibberellins (GAs), ethylene, and abscisic acid (ABA), plus the new plant hormones, brassinosteroids (BAs), and salicylates or salicylic acids (SAs) can be gathered into three groups. These are growth hormones, stress hormones and shock hormones. Auxin and CKs are growth hormones. Ethylene, GAs, and brassinosteroids are stress hormones. ABAs and SAs are shock hormones. All three types of hormones are similar in that they fall within the classic definition of an intercellular hormone. They are made by a cell and are meant to affect the behavior of other cells, either in nearby tissue or at the opposite end of the plant.

ABA, also known as abscisic acid plays a direct role in dormancy release and germination. Ethylene and the gibberellins group of hormones are indirectly involved.

1. INTRODUCTION

In general, seed dormancy refers to lack of growth due to any external or internal cause. It also refers to a state in which viable seeds fail to germinate even when given favourable environmental condition i.e. adequate moisture, appropriate temperature regime, a normal atmosphere and in some cases light.

There are various degrees of dormancy varying from very slight to very strong (deep). Sometimes the development or degree of dormancy changes during the lifetime of the seed, usually as a response to external conditions. Hence, dormancy may be innate, develop, be broken and redevelop in seed.

Several types of dormancy exist, and sometimes more than one type of dormancy occurs in the same seed. In nature, dormancy is broken gradually or by a particular environmental event. The type of event that may break dormancy depends on dormancy type. Dormancy caused by a hard seed coat may be overcome by a gradual or an instant abrasion, and darkness induced dormancy by exposure to light. In seed handling, the natural dormancy breaking mechanism is applied or simulated during the process of pretreatment. “Pretreatment” is a term used for conditions or processes applied to break dormancy prior to germination, while “treatment” is used for application of pesticides for control of pests and diseases.

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”.