eChapters

Previous Year Questions

1. Different Classes of Seeds?

2. Various parameters of field & seed standards for breeder seed production?

3. Factors that affect the longevity of seeds during storage in warehouses?

4. Initial Seed Quality?

5. Seed Testing?

Different Classes of Seeds

1. Nucleus Seed: It is handful of seed maintained by concerned breeder for further multiplication. The nucleus seed will have all the characters that the breeder has placed in it and it is of highest genetic purity. The quantity of nucleus seed is in kilograms.

2. Breeder Seed (BS): Breeder seed is a seed or vegetative propagating material directly controlled by the originating or sponsoring plant breeder of the breeding programme or institution and or seed whose production is personally supervised by a qualified plant breeder and which provides the source for the initial and recurring increase of foundation seed. Breeder seed is exempted from certification. However, the breeder seed crop is being inspected at appropriate stages by a Monitoring Team consisting of breeder, representative of NSC and representative of Seed Certification Agency. The breeder seed lots are affixed with Golden Yellow tags. The genetic purity of breeder seed crop should be maintained at 100 per cent.

Seed certification is a legal programme to maintain and make available to the public high quality seeds and planting material of genetically distinct crop varieties. Under seed production programme, quality seed is produced by govt. farms research stations, progressive farmers and seed producers using careful quality control, pedigreed plant stock, field inspections during the growing season and seed inspections after the harvest. Certification is an officially recognized method for maintaining varietal identity of the seed. In India certification is carried out by State Seed Certification Agencies.

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

I. FILL UPS

1. _____ is a legally sanctioned system for quality control on seed multiplication and production.
2. Certification consists of _____ phases.
3. In single application, the maximum area that can be offered for certification is _____.
4. AOSCA stands for_____.

Introduction

Seed certification is a legally approved system for quality control of seed multiplication and production. Seed certification procedures are designed to ensure physical and genetic purity, freedom from other crop seeds, objectionable and other weed seeds and designated diseases with good germinability of the foundation and certified seed. Seed certification is done by the State Seed Certification Agency of the concerned state (SSCA) notified under section 8 of the Seeds Act, 1966 or by National Seed Corporation (NSC), where State Seed Certification Agency does not exist. The General Seed Certification Standards are applicable to all crops, which are eligible for certification, while field and seed standards are applicable to individual crop, constituted as the minimum seed certification standards. The word ‘seed’ or ‘seeds’ as used in these standards also includes all the propagating materials. Seeds or propagating material, which does not meet the standards of seed certification prescribed in the Indian Minimum Seeds Certification Standards, 2013 (Gunasekaran and Trivedi, 2013), are not certified by the Seed Certification Agency. The general seed and field standards for various crops are given at the end of this chapter.

Seed multiplication and production was controlled by a legally sanctioned system called Seed Certification. Seed certification procedures and designed to ensure physical and genetic purity, freedom from weed seeds and diseases and good germinability of the certified seed. Seed certification is done by the Seed Certification Agency (SSCA) of the concerned state or by NSC.
 
Objectives of Seed Certification

The objective of seed certification programme was formulated by Douglas, 1971
 
i)    to ensure genuineness and quality of seed.
ii)    The identification and their rapid increase of new varieties under accepted names.
iii)    The systematic increase of superior varieties
iv)    Continuing supply of quality material and their maintenance.

Seed certification

It is a legally sanctioned system for quality control and seed multiplication and production. It involves field inspection, pre and post control tests and seed quality tests. As per Indian Seed Act seed certification is voluntary and it is not compulsory. The seed that is sold in the market is of two types certified seed or truthfully labelled seed. Whereas truthfully labelled seed is one which is being produced and marketed by the producing company by maintaining the labelling standards.

The collection of cones/fruits and seeds is the first step in the harvest, processing, and storage of seed in which man interacts with nature in determining ultimate seed quality. Successful collection, therefore, depends on understanding seed maturation and dispersal characteristics of each species, knowing local weather trends, and evaluating crop quality. Collection of propagating material is an expensive process and it is therefore also important that areas wherein cones and seeds are to be collected are evaluated to determine whether a sufficiently heavy crop to permit economic collection of seeds is present and whether the seed zone and elevation represented by the candidate area is appropriate for the production of seedlings needed in the reforestation program. Remember that properly collected, processed, and stored seeds may remain viable for a decade, so evaluation of seed needs may be projected well in advance of current harvest schedules through proper planning and organization of seed collection.

After harvesting and threshing, the seed usually arrives at the cleaning plant with trash, green leaves, weeds, other crop seeds and insects, etc. If the seed contains leaves, etc. and other high moisture materials, it cannot be accurately cleaned and safely stored until most of the foreign material has been removed. The process of removing the unwanted materials from a seed lot is known as seed conditioning. Seed conditioning is an essential component of seed technology to ensure that the farmers get the seed of high quality.

• The seed production of varieties and hybrids should be carried out carefully by following various techniques in the region where they are well adopted.
• The various factors affecting quality seed production includes,
  1. Agro climatic factors / Ecological factors - edaphic and climatic factors
  2. Production factors
  3. Post harvesting handling of seed
  4. Seed quality control factors

Concept of Delinting

Cotton seed clumps because of linters getting trapped on them after ginning. Gin-run seeds have very low flowability and do not singulate, making cleaning, upgrading, and precise metering in planting operations challenging or impossible. To singulate the seed and increase flowability, a variety of techniques have been and are employed. Most of the techniques entail removing the tags and linters entirely or partially, although other coating techniques have also been attempted with mixed results, both financially and technically (Mezynski, 1966; Webber and Boykin, 1907).

Methods of Delinting

1. Mechanical Delinting

Mechanical delinting is the usual technique used to improve the flowability of cotton seed. As previously indicated, mechanical delinting basically involves resharpening with finer, closer-spaced saws to remove part of the commercially valuable linters.

1. DEFINITION

Seed deterioration is defined as deteriorative changes occurring with time that increase the seed’s vulnerability to external challenges and decrease the ability of the seed to survive

I. FILL UPS

1. _____ is defined as deteriorative mechanism occurring with time that increase the seeds vulnerability and decrease ability to survive.
2. Lettuce seeds develop red necrotic lesions in cotyledons known as _____.
3. _____ morphological changes occur in ground nut due to deterioration.

The important events involved in seed development and maturation include

• Pollination
• Fertilization
• Development of the fertilized ovule by cell division
• Accumulation of reserve food material
• Loss of moisture content

A seed (in some plants, referred to as a kernel) is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed plants (started with the development of flowers and pollination), with the embryo developed from the zygote and the seed coat from the integuments of the ovule. In broad sense, seed is a material which is used for planting or regeneration purpose. Seed technological point of view, seed may be sexually produced matured ovule consisting of an intact embryo, endosperm and or cotyledon with protective covering (seed coat). It also refers to propagating materials of healthy seedlings, tuber, bulbs, rhizome, roots, cuttings, sets, slips, all types of grafts and vegetatively propagating materials used for production purpose. Quality seed, therefore, can be defined as the seed which fulfills the minimum requirements of getentic and physical purity, seed germination and vigour freedom from weeds and other crop seeds and other relevant seed standards.

Seed dormancy

Plants evolve many mechanisms that ensure their survival. For instance, some species produce prodigious number of seeds so that even if only a small proportion germinate and grow, some seedlings will survive. Alternately, dormancy can be defined as: a seed characteristic, the degree of which defines what conditions should be met to make the seed germinate. This definition may be more useful in understanding dormancy because it suggests that dormancy is variable, rather than constant, which is the situation that we generally encounter in the native populations of many species. The staggering of germination (dormancy) is an advantage for seeds that mature in late summer to early fall, since immediate germination would leave vulnerable seedlings exposed to harsh winter conditions.

I. FILL UPS

1. _____ refers to lack of growth due to any external or internal cause.
2. _____ refers to a state in which viable seeds fail to germinate even when given favourable environmental conditions.
3. _____ is a condition in which seed can germinate upon absorption of water.
4. _____ is otherwise known as primary dormancy.
5. A condition that develops to prevent germination after the seed has been detached from the plant is called _____.
6. Dormancy related to the embryo is called _____.

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.

Drying is an important unit operation in seed processing in order to maintain seed ability and vigor . it is advocated that seeds should be harvested soon after they attain physiological maturity to obtain better quality seeds and to minimize field losses. The traditional method of sun drying is inadequate, uncontrolled and time bound, which may not meet the high demand of quality seeds in time. Hence artificial drying, the effect of certain drying parameters like seed moisture content, drying air temperature, airflow rate, depth of seed loading and time of exposure on drying characteristics and viability of seeds are to be determined for safe and economical drying of seeds.

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.