Botany

Botany


What is Seed ?
Definition:


Seed is a mature integumented megasporangium or mature ovule consisting of embryonic plants together whit store food material covered by a protective coat (mega sporangium i.e. female gametophyte –the pistils are the female reproductive organs called megasporophylly in the flowering plants) the ovary of the carpel contains ovules (megasprorangia)
Definition of Seed technology:


Cowan (1973):


Defined as “That discipline of study having to do with seed production, maintenance, quantity and preservation


Feistritzer (1975):


Defined seed technology as the method through which the genetic and physical characteristic of seeds could be improved.


It involves such activities as variety development, evaluation and release seed production, seed processing, seed storage, seed testing, seed certification, seed quality control, seed marketing etc.


Role and Goal of Seed Technology in Crop Production


Role of Seed Technology:


Feistritzer (1975) outlined the few roles of improved seed.


1. Seed – a carrier of new technologies.
2. Seed – a basic tool for secured food supply.
3. Seed – The principle means to secure crop yields in less favorable production areas.
4. Seed – a medium for rapid rehabilitation of agriculture in case of natural disaster.


1. A carrier of new technologies:


The introduced of quality seed of new verities and combined with other inputs significantly increased yield level e.g. in cereals, yield increased up to 112%, in potato – 24% & sugar beet - 142% in U. S. A. & central Europe.


In India the cultivation of high yielding verities have helped to increase food production from 52 million tones (1947) to nearly 200 million tones in 2000-2001


2. A basic tool for secured food supply:


The successful implementation of the high yield verities programme in India has led to a remarkable increase the production.


As a result, food imports from other countries have been substantially brought down in spite of the rapid population increase.


3. The principle means to secure crop yield in less favorable area of production:


The supply of good quality seed of improved verities, suitable to these areas is one of the crops. Immediate contribution that seed technology can make to secure higher crop yield


Goals of Seed Technology:


The measure role of seed technology is to increase agriculture production through the spread of good quality seed of high yielding verities.


1. Rapid Multiplication:


Increase in agricultural production through quickest spread of new verities developed (released) by the plant breeders.


2. Timely supply:


The improve seeds of new verities must be made available well in time, so that farmer is planned planting schedule (or showing time) without disturbed. They are able used good seed for planning (sowing) purpose


3. Assured high quality of seeds:


Is necessary to obtain the expected dividends from the use of sees of improved verities


4. Reasonable price:


The cost of high quality seed should be within reach of the average farmer.
Seed Dormancy


Definition:


Non – germination of seeds due to absence of suitable conditions is termed as dormancy.


OR


A physical or physiological condition of viable seed, which prevents germination even in the presence of favorable conditions


The seed dormancy is divided in to three groups


1. Endogenous
2. Exogenous
3. Combined


Cause of seed dormancy/ factor responsible for seed dormancy


Genetical factor / cause:


1. Physiological
2. Embryo dormancy
3. Undeveloped cotyledon
4. Immature embryo


Coat imposed dormancy:


1. Seed coat factor:


a. Seed coat impermeable to water – i.e. water does not entered into seed coat
b. Seed coat impermeable to oxygen (0 is not entered in seed coat)
c. Mechanically resistant seed coat.


2. Embryo factor:


1. Dormant embryo
2. Immature/ Rudimentary embryo


3. Inhibitory factors:


Presence of germination Inhibitors in seeds i.e. presence of inhibitors or release of inhibitors.
Methods of Breaking Seed Dormancy


Various methods have been used by seed scientist and technologists to break the dormancy of seed.


Simple and widely used methods are


A. Scarification:


Any treatment i.e. physical or chemical that weakness the seed coat, is known as scarification.


Scarification method is applied, when dormancy is imposed by hard seen coat e. g. in legumes- cajanus cajan, (tur), gram etc.


In this method there are various way to break hard seed coat such as:
Seeds are either rubbed on a sand paper manually. At the time of rubbing care should be taken that not to damage the axis of the seed e.g. Green gram & subabool.
When seed coat is too hard i.e. of woody nature, the seed coat has to be removing completely by breaking it. E.g. Rubber (Havea app) seed India teak wood seed.
Soaking treatment: Soaking hard seed coat in concentrated or diluted solution of sulphuric acid for 1 to 60 minutes, it remove seed coat impermeability. E. g. cotton seeds, India teak wood seeds etc.


B. Temperature Treatments:
When the dormancy is due to embryo factor i.e. the seed is incubating at low temp. (0- 5o C) over a substratum for 3 to 10 days placing it at optimum temp. Required for germination. E.g. mustard. – (Brassica campestrits)
Some seeds required a brief period of incubation (from a few hours to one to five days) at 40 to 50 oC before germinating at required temp. ( in this method care should be taken that moisture content of the seed is not more than 15% e.g. paddy (Oryza Sativa)
Hot water treatment is also an effective method of breaking hard- seed ness in legumes. In this method the seeds are soaked in water at 80oC temp. For 1 – 5 minutes (depending up on the type of seed) before putting for germination.


C. Light Treatments:


Same seeds do not germinate in dark thus it provides continuous or periodic exposure of light is essential e. g. Lettuce (Lactuca Sativa) required red light (660nm) or white light is essential for germination to occur.


D. Treatments with growth regulators & other Chemicals:


Endogenous dormancy may be due to presence of germination inhibitors. Application of low level of growth regulators (i.e. Gibberellins, Cytokinins and Ethylene etc) may break the seed dormancy.


Most widely used growth regulators are gibberellins and kinetics e.g. seeds of sorghum crop presoaking seed treatment with GA3 at the conc. Of 100 ppm have been used for breaking seed dormancy


Among other chemicals potassium nitrate (0.2%) and thio – urea (0.5 to 3%) are widely used for breaking seed dormancy in oat (Avena Sativa), barley (Hordeum vulgare), tomato (Lycopersicon spp).


(For prepare 100 ppm solution of GA3, weigh 100 mg of GA3 & dissolve in a few drops of alcohol and make up the final volume (1000 ml) by adding distilled water).


(50 ppm kinetin 5 mg dissolved in few drops of alkaline made with sodium hydroxide and makes the final volume 100ml it gives to final conc. Of 50 ppm)
Principles of Quality Seed Production


During seed production strict attention must be given to maintenance of genetic purity and other qualities of seed in order to exploit the full dividends sought to be obtained by introduction of new superior crop plant varities.


Genetic principles:
Deterioration of varities:


Genetic purity (trueness to type) of a variety can be deteriorating due to several factors during production cycles.


The important factor & real deterioration of varities listed by Kadam (1942) & these are
Developmental variations
Mechanical mixtures
Mutations
Nature crossing
Minor genetic variations
Selective influence of diseases
The technique of plant breeder


Mechanical mixtures, natural crossing and selective influences of diseases are most important reasons for genetic deterioration.
Mechanical Mixture:


Mechanical mixture may take place at the time of sowing, it more than one variety is sown with same drill or through different varieties grown in adjacent field.


Two varities growing alongside each other the field are often mixed at the time of harvesting and threshing operation. Threshing equipments (i.e. threshing machine) is often contaminated with seeds of other varities.


The gunny bags, seed bines are also quite responsible mechanical mixture with seeds of other varities.


To avoid mechanical mixture, it must be necessary to rogue the seed fields and care should be taken at the time of harvesting, threshing and handling.
Natural Crossing:


In sexually propagated crops, natural crossing is most important source of vertical deterioration.


The deterioration in varieties due to natural crossing is of three reasons
Natural crossing with undesirable type
Natural crossing with diseases plants
Natural crossing with off- type of plants


According to Bateman (1947) genetic contamination is seed field due to natural crossing depends upon the some factors and these are
The breading system of species
Isolation distance
Vertical mass
Pollinating agents.


As the isolation between varieties is increased the contamination decreases. Isolation of seed crop is a primary factor in the seed production of crop plants of cross pollinated by wind or insects and their activities, humidity and temp. at the time of anthesis etc.
Selective Influences of Diseases:


New crop varieties often become susceptible to new races of diseases often caused by parasite.


Some vegetative propagated stocks deteriorate fast it infected by viral, fungal and bacterial diseases. It is very important to produce diseases free-seeds /stocks.


Genetic Purity during Seed Production


The various steps suggested by Hartmann and Kester (1968) for maintaining genetic purity.


The steps are
Providing adequate isolation to prevent contamination by natural crossing or mechanical mixtures.
Rouging of seed fields, prior to the stage at which they could contaminate the seed crop
Periodic testing of varieties for genetic purity
Avoiding genetic shift by growing crops in areas of their adaptation only.
Certification of seed crops to maintain genetic purity & quality seed.
Adopting generation system. (the seeds produced is restricted to four generation only i.e. starting from breeders seeds.) and the seeds can be multiplied up to three more generations i.e. foundations, registered and certified.
Grow-out – tests: The important factors / safeguards for maintaining genetic purity during seed production are


Control of seed source:


For raising a seed crop the seeds should be required from an approved source and from an appropriate class is necessary.


Four classes of seeds are generally recognized in seed certification namely breeder seed, foundation registered and certified. These classes are recognized by AOSCA i.e. Association of official seed certifying agencies.
Breeder’s seed: Is a seed or vegetative propagating material which is directly controlled by sponsoring breeder of institution & which provides increases of foundation seeds.
Foundation seed: is a seed stock so as to maintain specific genetic identity and purity and may be designated or disturbed by agriculture experiment station. Production must be carefully supervised by representatives of the station. Foundation seed is the source of all other certified seed classes, either directly or through registered seed.
Registered seed: Registered seed is the progenies of foundation and it is handled so as to maintain genetic identity and purity and that has been approved by and certified by certifying agencies.
Certified seed: Is the progeny of foundation, registered or certified seed, that is handled to maintain genetic identity and purity and that has been approved by and certified by certifying agencies.


Preceding Crop Requirements:


Preceding Crop Requirements has been fixed to avoid contamination through volunteer plants and also from soil borne diseases. (Volunteer plants mean plants grown in the field from previous crops).


Isolation:


Isolation is required during seed crop production to avoid contamination due to natural crossing and diseases infection by wind and insects from neighboring field and also during sowing, harvesting, threshing and handling of seeds to avoid mechanical mixtures.


The isolation distance is different from crop to crop and from different classes of seeds. i.e. certified seeds & foundation seed plots


Rouging of seed fields:


The off time plants i. e. plants offering in their characteristic from those of the seeds variety is another source of genetic contamination. Their continued presence would certainly deteriorate the genetic purity of the variety. The removal of such type of plant is referred as “rouging”.


There are three main sources of off- type
The off-type plant may be arises due to presence of recessive genes in heterozygous condition at the time of release of variety. (The recessive genes may also arise by mutation).
Off-type plants are due to volunteer plants or from seed produced by earlier crop.
Mechanical mixtures also constitute the major source foe off- type plants.


Seed certification:


The genetic purity in commercial seed production is maintained through a system of seed certification.


The objective of seed certification to maintain and make available crop seeds, tubers, bulbs, etc. which are of good seeding value and true to variety for seed certification purpose well experienced and qualified personal are required from seed certification agency & they carry out field inspection at appropriate stage of crop growth. They also make seed inspection variety the seed crop/seed lot is of the requisite genetic purity and quality.


After harvest crop they variety the quality and at the processing plants they take samples for seed testing and also for grow-out-test.


Grow- out – test:


Varieties being grown for seed production should periodically be tested for genetic purity by grow – out – test, to make sure that, seed being maintained in their true form.


Seed Purity


When a farmer buy a seed from any recognized institute or company, he expect to receive a good quality seed and not a mixture of other crop seed, weed seeds, straw etc. It is not possible to remove all these admixtures completely with the use of cleaning machine is & some seeds always remain present and there is necessary to take purity test or analysis, to determine how much % of the admixture is present in the seed.


To avoid admixture in seed of a particular variety or crop the buyer can be protected by the seed regulation laws or acts in many countries, for this purpose in many countries “seed testing stations or seed testing laboratory” are set up & these stations or laboratory are associated with ISTA (International seed testing association)
Stages of Seed Multiplication


The benefits of an improved variety are not released unless enough true seed has been produced for its commercial spread. The initial amount of pure seed which is limited in quantity is multiplied under various stages or classes or seed these are:


a. Nucleus seed b. Breeders seed c. Foundation seed
d. registered seed e. certified seed


Nucleus seed:


It is the initial amount of pure seed of an improved variety available with plant breeder who has involved it. The nucleus seed is sent per sent pure genetically as well as physically and is very limited in quantity.


Breeder’s seed:


It is the seed obtained from the progeny of nucleus seed. It is directly supervised by a breeder concern with the crop. Its genetically and physical purity to be 100 per cent.


Foundation seed:


It is seed obtained from nucleus or breeder’s seed. It is produced on seed multiplication farm of a state govt. or grill. Universities. Foundation seed plots are jointly inspected by the SCA (seed certification agency), it is not as pure as the nucleus and breeder’s seeds are. The bags are sealed with white colored label.


Registered seed:


It is raised from nucleus, breeders or foundations seeds. Registered seed growers are selected from progressive farmers. The maintenance of purity from time to time. The purity is maintained through field inspections by seed certifying agencies and seed tests.
The bags are sealed with purple colored label.


Certified seed:


It is progeny of registered or foundation seed. When the amount of seed registered seed id supposed to be inadequate to meet farmers agency. The bags are scaled with purple colored label.
Seed Certification




Seed certification is a legally sanctioned system for quality control of seed multiplication and production and which consists the control measures are
It is an administrative check on the origin of propagating material for the purpose of trueness to purity (genetic purity).
Field inspection: At the time of growing a crop for seed production purpose. The data should be obtained on trueness to varietals purity, isolation of seed crop to prevent crops- pollination, mechanical admixtures and diseases dissemination, objectionable weeds and admixtures.
Supervision on agricultural operations i.e. intercultural operations, harvesting, storage, transport and processing etc. for identity and quality of lots.
Sample inspection: For quality and to maintain genetic purity, a lab test of representative samples drawn by the S.C.A. for determining,% of germination moisture content, weed seed content, admixture and purity.
Bulk inspection: For checking homogeneity of the bulk as compared with the sample inspected.
Control Plot Testing: Samples drawn from the source seed and the final seed produced can be grown in the field along with standard samples of the variety.


The purpose of seed certification is to maintain and make available high quality seed and propagating materials of notified plant varieties.


Phases of Seed Certification


Seed certification has five phases of these are:
Verification of seed source.
Inspection of seed crop in the field.
Supervision at post-harvest stages including processing and packing.
Seed sampling and analysis.
Grant of certificate, certification tag, tables and sealing.


Concepts of Seed Certification


The AOSCA (association of official seed certifying agencies) have given some fundamental concepts of seed certification & these are:
Pedigree of all certified crops must be essential.
The integrity of certified seed growers must be recognized.
Field inspection must be made by through qualified field inspectors.
Verification trials to establish and maintain satisfactory pedigree of seed stock.
For keeping proper records to establish and maintain satisfactory pedigree of seed stock.
Standard should be maintained for purity and germination.
The principles of sealing seeds to protect both grower and purchase must be approved.


Steps Required for Organizing Seed Certification


The various steps are required for organizing seeds certification are:
Establishment and operation of seed certification agency.
Establishment of minimum seed certification standards.
Establishment of procedure for field inspection, seed processing, seed sampling and testing, tagging and sealing etc.









Seed Certification Agency


The broad principles for forming a seed certification agency are:


a. Should not involve in production and marketing seeds.


b. It should have a autonomy body.


c. The seed certification standards and procedure adapted by S.C.A should be uniform. The same standard and procedure should be adopted through out the country.


d. It is closely associated with technical institute. Its relationship with other institute should be clearly defined.


e. Should be operating on a no-profit-no loss basis.


f. Technique staff (adequate) trained in seed certification should be maintained.


g. Prevision for creating adequate facilities and timely inspections.


h. It should be served in the interests of seed produces and buyers.


Structure of Seed Certification Agency


a. Director: The director is responsible for the all over functioning of the company. He should be the member of secretary of the board of director and also the chairmen of various committees framed time to time with specific problem.


b. Supervisors (seed certification officers): For each group of related species under certification e.g. cereal seeds, vegetable seeds etc. He should the put in charge of supervising the field inspector’s work and observes the rules and regulations, minimum standers are met or not. He should trained seed inspectors and other personal involved in inspection.


c. Seed Certification Inspectors: He should be a trained and technical based of the seed certification system. During field inspection season, he must be willing to work long hours during peak period. He should be encourage and pursuable seed growers and seed producer to adopt new techniques and scientific finding. He should be good at public relation and also to guide and lead farmers by his devotion to work.


Duties and responsibilities of Seed Certification Agency


1. To arrange for suitable application, inspection and report forms.


2. To identify source of breeders seed. That can be used as the basis for further multiplication.


3. Through field inspection, that prescribes the minimum standard for isolation, planting ratio, raguing etc.


4. To assists seed growers and producers in obtaining suitable planting seed. This is especially in case of H.S.P.


5. To assists seed producer at the time of harvesting, drying & processing.


6. To draw a seed sample and inspect seed lots & submit such sample to the seed testing laboratory for maintaining the prescribed seed standards.


7. To issue appropriate seed certification tags for seed lots.


8. To maintain adequate records. So that the eligibility of specific lot can be determined in subsequent years.


9. Close working relationship between seed growers, dealers, research personals government’s officials, etc.


10. To take appropriate corrective actions against rigorously any violation of prescribed standards or complaints from uses of certified seeds.