Seed is any material used for planning & propagation whether it is in the form of seed (grain) of food, fodder, fiber or vegetable crop or seedlings, tubers, bulbs, rhizomes, roots, cuttings, grafts or other vegetative propagated material.
Seed is a fertilized ovule consisting of intact embryo, stored food (endosperm) and seed coat which is viable & has got the capacity to germinate.
As we say, “Reap as you sow”, the good quality seed must have following characters:
1. Seed should be genetically pure & should exhibit true morphological & genetically characters of the particular strain (True to type).
2. It should be free from admixture of seeds of other strains of the same crop or other crop, weeds, dirt and inert material.
3. It should have a very high & assured germination percentage and give vigorous seedlings.
4. It should be healthy, well developed & uniform in size.
5. It should be free from any disease bearing organisms i.e. pathogens. 6. It should be dry & not mouldy and should contain 12-14% moisture.
Seed is the basic input in the crop production which should be of good quality.
Seed Germination: Means the resumption of growth by embryo & development of a young seedling from the seed. Germination is an activation of dormant embryo to give rise to radical (root development) and plumule (stem development).Germination is the awakening of the dormant embryo. The proce4ss by which the dormant embryo wakes up & begins to grow is known as Germination.
Seed Emergence Means actually coming above and out of the soil surface by the seedling.
Changes During Germination:
1) Swelling of seed due to imbibition of water by osmosis.
2) Initiation of physiological activities such as respiration & secretion of enzyme.
3) Digestion of stored food by enzymes.
4) Translocation & assimilation of soluble food.
When seed is placed in soil gets favorable conditions, radical grows vigorously & comes out through micro Pyle & fixes seed in the soil. Then either hypo or epicotyls begins to grow.
Types of germination:
1. Hypogeal germination: The cotyledons remain under the soil. E.g.: cereals, gram.
2. Epigeal germination: The cotyledons pushed above the soil surface. E.g.: mustard, tamarind, sunflower, castor, onion.
Seed Dormancy: Failure of fully developed & mature viable seed to germinate under favourable conditions of moisture & temperature is called resting stage or dormancy and the seed is said to be dormant. Kinds of Dormancy in Seeds:
1. Primary dormancy: The seeds which are capable of germination just after ripening even by providing all the favourable conditions are said to have primary dormancy. E.g.: Potato.
2. Secondary dormancy: Some seeds are capable of germination under favourable conditions just after ripening but when these seeds are stored under unfavourable conditions even for few days, they become incapable of germination.
3. Special type of dormancy: Sometimes seeds germinate but the growth of the sprouts is found to be restricted because of a very poor development of roots & coleoptiles.
Causes of Dormancy:
The dormancy in seeds may be due to any single or a combination of more than one of the following causes.
1. Seed coats being impermeable to water: Some seeds have a seed coat which is impermeable to water. Such seeds even when fully matured & placed in favourable conditions; fail to germinate because of failure of water to penetrate into the hard seed coats. These seeds become permeable, if they are treated with H2SO4 or dipped in boiling water for few seconds. E.g.: Cotton.
2. Hard seed coat: Seeds of mustard, amaranths, etc. contain a hard & strong seed coat which prevents any appreciable expansion of embryo. Thus, if the seed coats fail to burst the embryo will remain dormant even after providing all the favourable conditions for germination.
3. Seed coats being impermeable to O: The seed coats are impermeable to O2 & if the seed coats do not rupture the seed fails to sprout.
4. Rudimentary embryo of seeds: The seeds which are apparently ripened contain a rudimentary or imperfectly developed embryo and the germination of such seeds naturally gets delayed until the embryo develops properly.
5. Dormant embryo: The seeds of an apple, peach, pinus, etc. do not germinate even though the embryos are completely developed and all the favourable conditions for germination are provided. In such seeds, physiological changes called after ripening take place during the period of dormancy which enables the seeds for germination.
6. Synthesis & accumulation of germination inhibitors in the seeds: Plant organs synthesize some chemical compounds which are accumulated in the seeds at maturity and these chemicals inhibit the germination of their seeds.
Multiplication & Distribution of Seeds
In India, farmers depend for their seed supply primarily on the state department of Agriculture and the National Seeds Corporation. The Department of Agriculture in all states has a planned programme of seed multiplication.
Classes of Quality seeds: The various classes of seed that are used in a seed production programme are:
1. Breeder seed: It is the seed or the vegetative propagating material produced by the breeder who developed the particular variety. The production & maintenance of breeders stock on main research station is controlled by the plant breeder. It is produced by the institution where the variety was developed in case the breeder who developed the variety is not available. In India, it is also produced by other Agri. Universities under the direct supervision of the breeder of the concerned crop working in that University, this arrangement is made in view of the large quantities of the breeder seed required every year. It is generally pure having high genetic purity (100%). Off type plants are promptly eliminated and care is taken to prevent out crossing or natural hybridization & mechanical mixtures.
2. Foundation seed: It is the progeny of the breeder seed and is used to produce registered seed or certified seed. It is obtained from breeder seed by direct increase. It is genetically pure and is the source of registered and/or certified seed. Production of foundation seed is the responsibility of NSC. It is produced on Govt. farms (TSF), at expt. stations, by Agri. Universities or by component seed growers under strict supervision of experts from NSC. It should be produced in the area of adaptation of the concerned variety.
3. Registered seed: It is produced from foundation seed or from registered seed. It is genetically pure & is used to produce certified seed or registered seed. It is usually produced by progressive farmers according to technical advice and supervision provided by NSC. In India, often registered seed is omitted and certified seed is produced directly from foundation seed.
4. Certified seed: It is produced from foundation, registered or certified seed. This is so known because it is certified by a seed certification agency, in this case state seed certification agency, to be suitable for raising a good crop. The certified seed is annually produced by progressive farmers
according to standard seed production practices. To be certified, the seed must meet the prescribed requirements regarding purity & quality. It is available for general distribution to farmers for commercial crop production.
Seed Production Organizations
Seed Production Organizations:
There are two types of Govt. / Public sector organizations responsible for seed production & certification in India. The first type of organization is represented by the National Seeds Corporation (NSC) which has responsibilities for the entire country. The second types of organizations are State Seeds Corporation (SSCs) and State Seed Certification agencies (SSCAs) that have state-wise responsibilities.
National Seeds Corporation:
The NSC was initiated in 1961 under the ICAR. Later, on 7th March, 1963, it was registered as a limited company in the public sector. It was established to serve two main objectives:
1) To promote the development of seed industry in India and
2) To produce & supply the foundation seeds of various crops.
The present functions of NSC may be summarized as:
a. Production & supply of foundation seed,
b. To maintain improved seed stocks of improved varieties,
c. Interstate marketing of all classes of seed,
d. Export & import of seed,
e. Production of certified seed where required,
f. Planning the production of breeder seed in consultation with ICAR,
g. Providing technical assistance to Seeds Corporation & private agencies,
h. Coordinating certified seed production of State Seed Corporation,
i. Conducting biennial surveys of seed demand,
j. Coordinating market research & sales promotion efforts,
k. Providing training facilities,
l. Providing certification services to states lacking established and independent seed certification agencies.
General principles of Seed Production
Production of genetically pure and otherwise good quality pedigree seed is an exacting task requiring high technical skills and comparatively heavy financial investment. During seed production strict attention must be given to the maintenance of genetic purity and other qualities of seeds in order to exploit the full dividends sought to be obtained by introduction of new superior crop plant varieties. In other words, seed production must be carried out under standardized and well-organized condition.
1. Deterioration of varieties: Genetic purity (Truness to type) of a variety can deteriorate due to several factor during production cycles. The important factors of apparent and real deterioration of varieties) are as follows:
a. Developmental variation: When the seed crops are grown in difficult environment, under different soil and fertility conditions, or different climate conditions, or under different photoperiods, or at different elevation for several consecutive generations, the developmental variation may arise sometimes as differential growth response. To minimize the opportunity for such shifts to occur in varieties it is advisable to grow them in their areas of adaptation and growing seasons.
b. Mechanical mixtures: This is the most important source of variety deterioration during seed production. Mechanical mixtures may often take place at the time of sowing, if more than one variety is sown with same seed drill; through volunteer plants of the same crop in the seed field; or through different varieties grown in adjacent fields. Often the seed produce of all the varieties are kept on same threshing floor, resulting in considerable varietal mixture. To avoid this sort mechanical contamination it would be necessary to rogue the seed fields, and practice the utmost care during the seed production, harvesting, threshing and further handling
c. Mutations: This is not a serious factor of varietal deterioration. In the majority of the cases it is difficult to identify or detect minor mutation. d. Natural crossing: In sexually propagated crops, natural crossing is another most important source of varietal deterioration due to introgression to genes from unrelated stocks which can only be solved by prevention
Natural crossing occurs due to following three reasons
i. Natural crossing with undesirable types.
ii. Natural crossing with diseased plants. iii. Natural crossing with off- type plants.
Natural crossing occurs due to following factors
i. The breeding system of species
ii. Isolation systems
iii. Varietal mass
iv. Pollinating agent
a. Minor genetic variations:
Minor genetic variations may exist even in the Varieties appearing phenotypically uniform and homogeneous at the time of their release. During later production cycle some of this variation may be lost because of selective elimination by the environment. To overcome these yields trials are suggested.
Selective influence of diseases: The selective influence of diseases in varietal deterioration is also of considerable importance. New crop varieties often become susceptible to new races of diseases often caused by obligate parasites and are out of seed programmes. Similarly the vegetatively propagated stocks deteriorate fast if infected by viral, fungal and bacterial diseases. During seed production it is, therefore, very important to produce disease free seeds/stocks.
b. Techniques of plant breeders:
In certain instances, serious instabilities may occur in varieties due to cytogenetically irregularities not properly assessed in the new varieties prior to their release. Other factors, such as break down in male sterility, certain environmental conditions, and other heritable variations may considerably lower the genetic purity.
Maintenance of Genetic Purity During seed Production:
The various steps suggested), to maintain varietal purity, are as follows.
a. Use of approved seed only in seed multiplication.
b. Inspection and approval of fields prior to planting.
c. Field inspection and approval of growing crops at critical stages for verification of genetic purity, detection of mixtures, weeds, and for freedom from noxious weeds and seed borne diseases etc.
d. Sampling and sealing of cleaned lots
e. Growing of samples of potentially approved stocks for comparison with authentic stocks.
The various steps suggested for maintaining genetic purity are as follows:
a. Providing adequate isolation to prevent contamination by natural crossing or mechanical mixtures
b. Rouging of seed fields prior to the stage at which they could contaminate the seed crop.
c. Periodic testing of varieties for genetic purity.
d. Avoiding genetic shifts by growing crops in areas in their adaptation only.
e. Certification of seed crops to maintain genetic purity and quality of seed.
f. Adopting the generation system. g. Grow out tests.
1. Selection of a Agro-climatic Region A crop variety to be grown for seed production in an area must be adapted to the photoperiod and temperature conditions prevailing in that area.
2. Selection of seed plot the plot selected for seed crop must be free from volunteer plants, weed plants and have good soil texture and fertility the soil of the seed plot should be comparatively free from soil borne diseases and insects pests.
3. Isolation of Seed crops the seed crop must be isolated from other nearby fields of the same crops and the other contaminating crops as per requirement of the certification standards.
4. Preparation of Land Good land preparation helps in improved germination, good stand establishment and destruction of potential weeds. It also aids in water management and good uniform irrigation.
5. Selection of variety The variety of seed production must be carefully selected, should possess disease resistance, earliness, grain quality, a higher yielder, and adapted to the agro climatic conditions of the region.
6. Seed treatment: Depending upon the requirement the following seed treatment may be given
a. Chemical seed treatment.
b. Bacterial inoculation for the legumes.
c. Seed treatment for breaking dormancy.
1. Time of planting The seed crops should invariably be sown at their normal planting time. Depending upon the incidence of diseases and pests, some adjustments, could be made, if necessary.
2. Seed Rate Lower seed rates than usual for raising commercial crop are desirable because they facilitate rouging operations and inspection of seed crops.
3. Method of sowing The most efficient and ideal method of sowing is by mechanical drilling.
4. Depth of sowing Depth of sowing is extremely important in ensuring good plant stand. Small
seeds should usually be planted shallow, but large seeds could be planted a little deeper.
5. Rouging: Adequate and timely rouging is extremely important in seed production. Rouging in
most of the field crops may be done at many of the following stages as per needs of the seed
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