eChapters

1. SEED STORAGE

Is the maintenance of high seed germination and vigour from harvest until planting.

1.1. Importance of seed storage

Seed storage is important to get adequate plant stands in addition to healthy and vigorous plants.

1. SEED TESTING

The science of evaluating the planting value of seed has been developed to achieve the following objectives for minimizing the risks of planting low quality seeds.

To determine the seed quality and its suitability for planting

To identify seed quality problems and their probable cause.

To determine the need for drying and processing, if any.

To determine if seed meets established quality standards for labeling.

To establish quality and provide a basis for price and consumer discrimination among lots in the market.

Founded in 1924, with the aim to develop and publish standard procedures in the field of seed testing, with member laboratories in over 70 countries world wide. ISTA membership is truly a global network. ISTA secretariat is located at Zurich, Switzerland.

1. VISION AND MISSION

ISTA members work together to achieve their vision of ‘Uniformity in seed quality evaluation worldwide’. The association produces Internationally agreed rules for seed sampling and testing, accredits laboratories, promotes research, provides International seed analysis certificates and training and disseminates knowledge in Seed Science and Technology. This facilitates seed trading Nationally and Internationally and also contributes to food security.

1. INTRODUCTION

For maintenance of genetic purity in the field with the seed crop and to test verify the standards in certification programme, the studies on varietal characterization and identification have attracted the attention of breeders, breeder’s right protection institutions, farmers, the seed industry, certification agencies, and seed testing laboratories with a view to assure the quality of seed marketed to the consumers.

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.