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Seed Processing_ Storage and Testing

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					          Seed Processing, Storage and Testing
                                   Booklet No. 252
                         Seed Production: Technology: SPTS - 2

Contents
Preface
I.     Introduction
II     Cause of Problems in Seed Storage
III.   Safe Drying of Seed
IV.    Requirements for Seed Drying
V.     Methods of Seed Drying
VI.    Seed Cleaning and Upgrading
VII.   Operations Required for Improving Seed Quality
VIII. Seed Storage
IX.    Seed Testing
X.     Seed Health Test
XI.    Seed Certification
XII.   Conclusion

Preface

       Quality seed is one of tile most important input factors governing the yield potential of a
crop. Use of unhealthy insect and disease attacked seed will just bring the disaster to the
farmers. Therefore it is imperative to supply farmers quality seeds of various crops. This booklet
describes the various aspects of processing storage and testing of tile seeds.

Dr. K. T. Chandy, Agricultural & Environmental Education

I. Introduction

        Freshly harvested and threshed seed is generally fit for growing a new crop. But it has to
be stored for some period ranging from a few days to numerous years, because of unfavourable
climatic conditions or dormancy for germination or for national reserve. The raw seed is,
through genetically pure, it contains a lot of undesirable materials like weed seeds, seeds of
other crops or varieties and damaged seeds. Therefore, it has to be processed and upgraded
for better and uniform crop stand in the next crop season.

II. Cause of Problems in Seed Storage

       The main cause of problems which damage the seed quality in stores is the moisture
content of tile seed. Moisture content of a few crop seeds are in table 1 given below.

                      Table 1: Moisture contents of freshly threshed seeds

                          Sl.   Seed                   Moisture
                          No                           content
                          1     Maize                  30-35 %
                          2     Wheat                  16-17 %
                          3     Rice                   20-21 %
                           4       Oats                    17-18 %

         The deterioration in seed quality is initiated at moisture content above 15% due to mould
growth, heating due to increased respiration and activities of micro-organisms. The seed start
germination at 30 -35% moisture content. To avoid such losses in seed quality and to maintain
it, the seed has to be artificially dried to 10 -12% moisture content before storing. The table 2
gives maximum moisture content for safe storage.

                      Table 2: Maximum moisture content for safe storage

                               Sl.No Crop                Maximum
                                                         moisture
                                                         content (%)
                               1     Wheat               12
                               2     Oats                13
                               3     Barley              13
                               4     Sorghum             12
                               5     Shelled corn        13
                               6     Soyabean            11
                               7     Rice                12

III. Safe Drying of Seed

        Moisture is a fundamental and ubiquitous part of the seed. Its content in the seed
depend upon the relative humidity and temperature of air. The moisture moves from the centre
of the seed towards the seed coat by the influence of the temperature of seed, while the
moisture from the surface of the seed coat is influenced by the drying air. A generalized
relationship among seed moisture content, relative humidity and seed temperature are in table 3
given below.

   Table 3: Generalized equilibrium condition of seed moisture at varying temperatures and
                                     relative humidities


                           Sl.No    Seed            Temperature
                                    moisture
                                    (%)
                                                    15C          25C
                                                    relative %   humidity
                                                                 %
                           1        17              83           85
                           2        16              79           81
                           3        15              74           77
                           4        14              68           71
                           5        13              61           65
                           6        12              53           58


IV. Requirements for Seed Drying
        Seed has to be dried as soon as it is harvested. For safe drying of the seed, so that its
germination do not drop more than 2%, certain conditions are to be taken care of. They are: (1)
holding time before drying commences, (2) air-flow during drying, (3) static pressure during
drying, (4) humidity of the drying air, (5) drying temperature arid (6) seed depth during drying.

1. Holding time before drying
        Wet seed must be subjected to drying as early as possible, since it is very likely to be
damaged by moulds, high temperature etc. Under unavoidable circumstances it may be
temporarily kept at aeration @ 1 cub. m/min cub. m seed to prevent rise in temperature and to
avoid damage to seed viability. Under field conditions, seeds are spread on the floor in thin
layer, but never keep them. If the layer is thick, periodic stirring is done to aerate all the seeds.

2. Air flow during drying
         A uniform air -flow keeps the seed homogeneous, without affecting the viability of the
seed. Air-flow is influenced by the kind of the seed, depth of the seed and static pressure etc.
An air-flow of 15 cub.m/min/cub. m seed for maize, 40 cub.m/min/cub.m seed in open drying
floor and 8 cub.m/ min/cub.m an average for most of the cereal seeds is required for satisfactory
drying.

3. Static pressure
        A resistance to air -flow through the seed is called the static pressure. It is determined by
the kind of seed, its depth, its moisture content and rate of air -flow. When drying bed is only
one sack deep a static pressure of 2.5 cm of water gives and excellent airflow for drying. Air-
flow can be accelerated in the field condition by using fans or exhaust fans.

4. Humidity of the drying air
        The rate of moisture removal from the surface of seed is influenced by the humidity of
the drying air. As the air is heated, its relative humidity goes down, and it increases the rate of
drying. The table-3 (given above) explains the effect of relative - humidity in drying the seed. For
example an air at 250 C with relative humidity as low as 58% can dry the seed, by removing all
moisture, higher than 12 per cent. But the same air with relative humidity 85% can remove all
moisture higher than only 17 per cent. Therefore as the relative humidity of air at a given
temperature goes up its ability to withdraw water from the seed drops. At any given
temperature, it is physical structure, chemical composition of the seed, seed coat permeability
and moisture percentage of the seed unitedly on one side and relative humidity of the air on
other side which set up a balance between moisture retaining tendency of the seed and
moisture with-drawing tendency of the air. The air and seed are then said to be in equilibrium
when seed either looses moisture or takes it. Table -3 (given above) this situation for 15°C and
25o C temperature when grain has 17% moisture, it is in equilibrium with 150 C air at 78%
relative humidity and if the air bas a higher relative humidity than 78%, no drying can be done.
Moreover if relative humidity drops lower than 78% , the seed moisture percentage decreases.

5. Drying temperature
        Temperature of the air influences the seed temperature and also the relative humidity of
the air and thereby controls the rate of drying the seed. Drying time in bours can be estimated
by the equation.

                         35.44 x MR
               t = --------------------------
                             F x TD
               Where.
               t = drying time in hours.
               35.44 = a constant,
               MR = Moisture removed (20 litres /cub.m seed),
               F = air flow cub.m/min/cub.m seed, and
               TD = temperature drop (Co).

        The temperatures exceeding 43°C or II0oF are detrimental to the viability of the seed.
therefore, the temperature of incoming of air should not be higher than this limit. The table 4
gives the recommended temperature of various crop seeds.

    Table 4: Temperature recommended for drying for various crops and their depth in bins.
                      Sl.     Seed             Temperatur Depth
                      No                       e               (cm)
                                               (degree C)
                      1       Shelled corn     43              50
                      2       Wheat            43              50
                      3       Barley           40              50
                      4       Oats             43              90
                      5       Rice             43              45
                      6       Soyabeans        43              50
                      7       Peanuts          32              150
                      8       Grain sorghum    43              50

6. Seed depth during drying
       Depth of the wet seed layer in the container offers an increasingly more resistance to air-
flow and creates an atmosphere of high temperature and high relative humidity which slows
down the drying process which becomes injuries to the seed viability. In field conditions spread
seeds into thin layer.

V. Methods of Seed Drying

      The drying of seed is done by two methods viz. sun drying and forced air drying. These
methods are described here.

A. Sun drying
        Most of the moisture content of seeds have to be reduced in the field before harvest, and
later on drying it on the threshing floor in sun heat. The main advantage of sun drying is that it
requires no additional expenditure. The disadvantages of this type of drying are delayed
harvests, risk of weather damage and increased likelihood of mechanical admixtures.

B. Forced air drying
        This method of seed drying is highly technical and requires a constant care while drying,
since first hot air is made to flow through the moistured seeds which absorbs water. In general
air of 43°C at relative humidity 60% blowing at the rate of 8 cub. m/ min/cub.m seed with a static
pressure of 8.75 cm of water is used. This method is supplied for the drying of seeds for several
cereal crops such as maize, wheat, oats, rice, sorghum, etc.

       The type of drier that is best suited for a particular situation depends upon (1) volume of
seed to be dried in a season, (2) the length of the drying season, (3) the size of seed lot, and (4)
the handling or transportation methods to be used. There are several types of driers such as: (a)
bag driers, (b) box driers, (c) wagon driers, (d) bin driers, and (e) continuous flow tower drier.

1. Bag driers
        Mostly the bags are used to pack the seed after threshing in small scale farms.
Convenient way to reduce the moisture of seed from 30% to 12% is to dry them by opening and
repacking. This is done in specially prepared bag-driers unit, where bags containing seeds of
different varieties with label are staked and a flow of air 40 cub.m/min/cub.m of seed at 3 cm of
water static pressure is adjusted till the seed becomes properly dry.

2. Box drying
       This method of drying is quite similar to the bag driers, only that in place of gunny -bags,
the boxes generally made from wood, plastic, metal, with perforated bottoms are used. Wet
seed is filled in box, which is kept over the drier -unit and removed after the seed is dried.

3. Wagon drying
        Wagon drying is a special type of drying technique, the threshed seed is loaded on a
specially constructed wagons, which are then taken to drier and connected to hot -air pipe to dry
the seed without unloading it. The wagons with dried seed are emptied into the storage bins.
This method of drying seed is very useful in lowering the cost of the operation and also saves
the time.

4. Bin drying
        When tile quantity of seed to be dried, exceeds 5 tonnes to 100 tonnes, the perforated
floor drying bins are very practical for drying and storing. The fan of sufficient size to deliver 8
cub m of air /min/cub. m of seed against a static pressure of 8.75 cm of water for deep -bed
seed drying in bin is recommended. The drying capacity of a bin is estimated by the time taken
to dry the seed. Similarly, the drying time in hours can be calculated with the equation
mentioned earlier.

        This determines how long it takes seed to dry at a particular depth, from which the drying
rate for the whole bin is derived. Actually all the seeds in tile drying bin may be considered to be
in three zones: (1) the dried zone (2) the drying zone and (3) the wet zone. As the air enters the
seed, the region nearest the inlet dries first. This dried zone gradually moves upward as drying
proceeds. The region below the drying front is characterized by dry seed and higher
temperatures and that above the drying front by moist seed and lower temperature. The width of
drying zone depend upon the volume of air flowing through the seed and its relative humidity.
An equality in temperature of the top-layer of seed and incoming air indicates that drying has
been completed.

5. Continuous flow tower drier
        Seed corporations, seed farms and private seed industries, which are engaged in
production of seed in large scale, use continuous flow tower driers. These type of driers are
mostly used in grain drying than in seed drying because of the risk of contamination by varietal
mixture. They are useful for drying of very large quantities of seed of one variety in seed
industry. In continuous flow driers seed moves through heating and cooling sections of the
column metering devices at the lower side of the seed column. Heated air is forced through the
upper 2/3 to 3/4 of the seed column.
VI. Seed Cleaning and Upgrading Ii
         Seed lots usually contain inert material, weed seeds, deteriorated and damaged seeds,
off-size seeds, etc. Seed cleaning and upgrading to remove or reduce to the extent possible the
various undesirable material and to get a uniform size seed so as to upgrade its overall quality
is a must. The cleaning process is done on the basis of differences in physical properties of
desirable seed and undesirable matter i.e. seed size density, shape surface texture, colour,
affinity for liquids and seed conductivity. Most often, satisfactory processing requires that lots be
processed in a specific sequence through several operations. Few examples are given below.

I. Sequence of seed flow for maize seed
       Receiving -> sheller -> air-sieve cleaner -> width-thickness
       grader -> length grader -> gravity separator -> treater -> bagger.

2. Sequence of seed flow for rice seed
       Receiving -> scalper -> air-sieve cleaner -> length, grader ->
       width grader -> treater -> bagger.

3. Sequence of seed flow for wheat, barley, oats and rye seeds
       Receiving -> scalper -> debearder -> air-sieve cleaner ->
       length grader -> gravity separator -> treater -> bagger.

Vll. Operations Required for Improving Seed Quality

       The operations and machines required for seed -processing, depend on the kind of
seed, the nature and kind of adulterants in, the seed lot and final quality required. The usual
operations are described here.

I. Preconditioning
       Freshly harvested seeds of many crops like blue -grass has, cob-webby hairs on seed,
oats and barley have awned seeds, maize cobs bearing seed and incompletely threshed heads
of wheat cause quite often hindrances in the crop -seed flow, during advanced stages of seed
processing. Therefore, it has to be decided, on the economic grounds to remove such
obstacles before processing of seed is initiated. These operations of pre -conditioning are
performed by using specialized machines for different crops specific crop like maize sheller for
maize, debeader for oats, scualper and rough cleaner for some other crops etc.

2. Basic cleaning
       The separation of light chaffy material, light-weighted, immature, deteriorated and insect
damaged crop seed, heavier trash and dust, constitute the basic process of cleaning.
Consequently, in basic cleaning, separations are made mainly on the basis of two physical
properties i.e. size and density of the seed.

3. Finishing operations
        The air-sieve cleaner alone cannot always process the seed to a desired seed -quality
standard. Precise separations are done with the help of two types of length separators. The
density -table is the best known of the density separators for a classification into various grades
and removing badly deteriorated, diseased, insect-damaged crop seeds.

4. Seed treatment
       Seed is covered with some organic compounds to protect it from storage loss or loss to
the germination young seedlings by organism like fungi, bacteria and virus in the soil. The seed
treatment is generally done with materials in the form of dust, wettable powders or liquids. Seed
dressing drum or quick wet method are generally used for this purpose.

VIII. Seed Storage

       Seed reaches physiological maturity on the plant before harvesting. At the stage it has
maximum viability and vigour, which get lost in due course of time. The loss in germination
potential cannot be stopped, but it can be retarded to get prolonged seed -life by improving the
seed storage conditions.

A. Factors influencing storage life
       The most important factors influencing germination potential in storage are discussed
here.

1. Relative humidity and temperature
        The two factors i.e. relative humidity and temperature determine the rate of seed
deterioration. Two simple rules are useful measures on the effect of moisture and temperature
on seed life as these control seed moisture content.

Rule 1 For every decrease in percentage of seed moisture content (14% to 50%) the life of the
seed is doubled.

Rule 2 For every decrease of 5°C in storage temperature (below 32°C), the life of the seed is
doubled. Table-6. explains the first rule, while Table 7. explains the suitable seed moisture
contents for seed storage.

           Table 6: Storage life of cereal seeds stored at different moisture contents

                            Sl.No     Moisture      Storage life
                                      contents
                                      (%)
                            1         11-13         6 months
                            2         10-12         1 year
                            3         9-11          2 years
                            4         8-10          4 years

                  Table 7 : Seed moisture level and their affect on stored seed

                        Sl.No Seed        moisture Changes in stored
                              above                seed
                        1     40%                  Germination occurs
                        2     18 %                 Heating may occur
                        3     12%                  Mould grow on and
                                                   in seed
                        4       12%                Fumigation     may
                                                   hurt germination
                        5       10%                Sealed storage is
                                                   unsafe
                        6       9%                   Insects multiply


       Therefore, seed having moisture contents between 9 -14% I should be stored in
temperature below 30°C. For bulk short-term storage of certified seed, adequate protection can
be provided by use of insulation material, vapour proof walls and judicious ventilation.

2. Oxygen and carbon dioxide content :
       The concentration of low oxygen and high carbon dioxide, when moisture content of the
seed is below 10%, increases the f seed life, while the same concentration when seed moisture
is above 10% reduces the seed life in cereals.

3. Direct sun light on the seed
       Infra-red light of the sun -light increases the seed temperature, thereby reducing its
storage life. The seed kept in open must be covered with black-cloth or turpauline materials.

4. Kind or seed
        The storage life of the seed seem to be an inherited attribute. Different varieties of the
same crop species exhibit various response to the loss of germination capacity, when stored
under similar conditions. Similarly different kinds of the seed, even under the same storage
conditions some seed lose the ability to germinate faster than others.

5. Previous history or the seed I
        The previous history of seed lot prior to a specific storage period also influence the
speed of germination loss during storage, such as: (1) weathering in the field, (2) mechanical
injury during harvesting and cleaning,. (3) heat damage during drying and (4) previous high
moisture periods.

6. Moisture contents or the seed
        The ideal long term storage, where all deleterious factors are eliminated, a moisture
content of below 9% is necessary. This will also increase the storage life by slowing the aging
process. If the seed is stored with moisture contents more than 14% then seed destroying
factors like growth of moulds, insects, damage by rodents, effects of fumigation and seed
treatment etc. will become pronounced and seed quality may be lost.

B. Protection from insect and fungal damage
        The protection of stored seed from different types of injuries such as those caused by
insect pests and diseases is very important. Some common measures are suggested here to
control them.

1. Use of insecticides
       The floor and walls should be sprayed with residual insecticides like DDT (50% WP) 1 -
2g/sq. m or Malathion (25%WP) 1.2 g/sq. metre.

2. Fumigating the stores
       Fumigation of gas tight stores when air temperature is below
300C and seed moisture is below 12% with Methyl bromide ( 16 -32 mg/litre) or Hydrogen
cyanide (32 -54 mgnitre) for 24 bours and Hydrogen phosphide (5 -10 tablets tonne of seed for
3 –7 days should be carried out.

3. Installation of advanced amenities
       Seed must be stored in room or go downs having all advanced facilities like (i) moisture-
vapour proofing, (ii) insulation, (iii) refrigeration, (iv) dehumidification, (v) desiccants etc.

4. Use of proper packaging material
        Packaging material must provide protection against high relative humidity. Under dry
warehouses and storage condition, the use of cotton, jute and paper bags is the most
satisfactory method of seed packaging. While in high -humidity location, some moisture-proof
containers like aluminum –polythlene laminated pouches, polyethylene bags of over 700 gauge
thickness, sealed tins etc. are good for this purpose.

5. Use of natural insecticides
        The natural insecticides of plant origin known as plant products have been used since a
long time. They are commonly known as grain protectants. They act as repellents, deterrents,
rodenticide and insecticides in the stored grain pest control programme.

a. Repellents
        Some of the plant species from which these repellents are derived are: (a) Azadirachta
indica, (b) Trigonellafoenumgraeum, (c) Artemisia absinthium, (d) Acorus calamus, (e) Valariana
officinalis, (f} Xanthoxylum armalus, and (g) Artemisia maritime.

       These possess repellency is against many insects like grain moth (Sitotroga cerealella),
rice weevil (Sitophilus granarius) and red flour beetle (Tribolium castaneum). The rice grains are
treated with turmeric powder, mustard oil and common salt for protection against insect
damage.

b. Deterrents
        The plants like (a) Acorus calamus, (b) Saussrea lappa, (c) Skimmia laureola, (d)
Sanlaillm album, and (e) Azadirachta indica are used as insect deterrents.

c. Insecticides
       Several plant products have been found to be toxic on stored grain insects.

i. The seed powder of Azadirachta indica @ 2% protects wheat flour from Sitophilus oryzae,
Trugoderma granarium for one year.
ii. The above powder also protects moong, gram, cowpea and
peas against C. maculatus for 8 -9 months.
iii. The same powder also protects paddy from R. dominica and S. cerealella.
iv. Lympholized oil from lemon, grape, and lime are highly toxic to the pulse beetle C.maculatus
v. Piper nigrum when grounded possess high toxic effect against S. oryzae damage.
vi. Allium sativum oil contents are toxic to T: granarium.
vii. The extract of A. calamus is toxic to C. chinensis, S. oryzae, T: granarium, and Corcyra
cephalonica.
viii The powder of plant specius A. calamus, A. sativum, A. indica, Carum corticum and X.
armatum controls the insects like R. dominica, S. granarins and S. cerealella.
ix. The plant materials of A. indica, Casia absus, lmpomoea hederaceae, Mentha arvensis, M.
sylvestris and poganum harmala show high insecticidal activity against S. oryzae.

IX. Seed Testing

       Evaluation of the quality of the seed has been practised by the farmers and gardeners,
by using their senses like looking, feeling, smelling and even tasting. They have developed an
ability to discard seed -lots of low -quality. However, many deficiencies in seed cannot be
detected by such simple methods and consequently low quality seed may be used, leading to
thin and poor crop stand and wastage of all inputs and growing season. Therefore, a reliable
seed test, conducted by seed-testing laboratories, will avoid the use of inferior seeds. Seed
testing is done for judging the following aspects of plant life.

A. PurIty analysis
       Purity of seeds can be acertained by the following methods.

1. Size of the sample
        A seed sample from a well blended seed lot is taken. A sample of 900 gm for maize, 40
gm for rice and 120 gm for wheat etc. is taken.

2. Pure seed
        Pure seed fraction includes: (a) mature and undamaged seeds, (b) under-sized,
shriveled, immature and germinated seeds, (c) pieces of broken seed, (d) diseased seed, (e)
grass or cereal florets with an obvious endosperm, and (f) free caryopsis.

3. Seeds of other crops and weeds
       This fraction of the seed includes seed of other crops or plants recognized as weed and
bulbets or tubers.

4. Inert matter
        Inert matter consists of mainly (a) empty florets, (b) broken pieces, (c) pieces of straw,
chaff, glume, soil and sand, (d) empty fruits or seeds of weeds, and (e) smut balls, ergots and
nematode galls.

B. Germination test
        The prescribed number of seed for germination test is 400, which can be divided into
four batches of 100 seeds or eight batches of 50 seeds. These lots are tested separately for
their germinability by adopting following methods.

1. Seeds are grown in sand or blotter at 250 C for maize and rice and at 200 C for wheat and
barley. Dormancy in rice is overcome by presoaking for 24 hours in water at 400C and in wheat
by pre-chilling up to 7 days at a temperature 5°C and to 10°C. Fungicide treatment with 1 %
sodium hypochlorite for surface sterilization of seeds is undertaken only upon request.
Germinated seedlings are classified into (i) normal (ii) dormant (iii) ungerminated and (iv) dead.
2. Germination test by using tetrazolium salt is one of the best method of finding the viability of
seeds. It is very useful test for rapidly obtaining an indication of germination potential and
viability of samples. It requires more work, attention and experience.
3. The X-ray technique is well established as non-destructive test for the assessment of insect
damage and infestation, underdeveloped, mechanical damage and poly embryony in seed. With
the BaCl2 contrast method, dead seed can also be distinguished and thus an indication of
germination potential is obtained.

C. Moisture determination
       Sample is analysed for moisture content promptly on the same day. The standard
method for moisture determination for maize, rice, and wheat is to dry the sample in a hot air
oven at 1300C for one hour, as per description laid down by international rules for seed testing.
D. Cultivar purity
        Sample of seed along with the authentic sample of cultivar are grown in the greenhouse
or in field plots to carryout constitute the grow -out -test. Morphological and physiological
characteristics of the seed, seedling and plant are examined and compared with the recorded
one.

X. Seed Health Test

       Many diseases like smuts in cereals and downy mildews on tobacco are transmitted by
seed. Seed functions as the vehicle for conveying serious pathogens to new areas. These
diseases not only destroy tile main crop but also the neighboring crops. The pathogen per
petuates in the soil affecting subsequent crops. Many procedures for testing seed health before
sowing have been developed.

1. Use disease free seed
       The best approach to control the seed born diseases is to prevent their occurrence by
using only disease free seed or following seed treatment if healthy seeds are not available.

2. Produce seed in disease free regions
       To escape from disease infection, the seeds should be grown in disease free areas.
Regions notorious for specific diseases outbreak should never be selected for growing the
seeds of susceptible crops.

3. Dry seed observation
        The dry seed, especially its inert matter is examined by using a low -power stereoscopic
microscope, with magnification up to 50 : -60 times, to detect the pathogens for disease like
sclerotic (Claviceps purpurea), fruiting bodies in flax (Septoria linicola), galls of nematodes, bunt
or smut balls in cereals and grasses, symptoms of infection of anthracnose and bacterial blight
in beans etc.

4. Incubation test
        Inoculum for many pathogens is present mainly in the form of mycelium in the seed and
can be properly assessed only through incubation. For this seed are sown on moist absorbent
paper (the blotter test) or in petri-dishes on agar (Agar test) for one week at 18 to 22°C. To
stimulate sporulation of fungi, standard illumination of a near-ultraviolet light-darkness cycle of
12/12 is provided. The seeds are examined under a low stereoscopic microscope, and numbers
of infected seeds are recorded and results are given in percentage. Incubation test is
particularly useful for detecting fungi, which readily produce conidia, in cereals, vegetables,
ornamentals, forest trees specially for the genera Alternaria, Ascophyta, Botrytis, Colletotricum,
Drechslera. Fusqrium. Myrothecium and Phoma.

5. Seedling symptom test
       In this test the seeds are grown by providing all possible natural conditions for
germination and growth of fungi often at low temperature, such as 10- 12°C to enable the
fungus grow, or high temperature such 200C for developing symptoms of Septaria and
Drechslera spp on cereals. Records are made after 2 -4 weeks of incubation.

6. Growing. on .tests
       Diseases like downy mildews and wilts do not attack seedlings. Therefore, plants are
grown in quarantine houses and observations are made in plots for detection of pathogens of
these diseases to prevent the dangerous effect of the pathogen in the next growing season.

7. Seed treatment
         Seeds of all cereals are treated with organo-mercurial compound @ 2 g/kg of grain,
before sowing as a precaution, to protect them from seed-born diseases. Freshly purchased
certified seed is generally sold as treated one.

XI. Seed Certification

        Seed of the new crop varieties, superior in some quantitative and qualitative
characteristics to existing ones, should be made available in appreciable quantity to farmers in
area for which the varieties are most suitable. The farmers those who purchase seed should be
sure of buying good seed of specific varieties. To provide a reasonable guarantee of the genetic
quality of seed prior to sowing, seed quality control systems works in India with the aim of
thorough supervision of the entire production of the seed. This involves keeping records of the
multiplication of varieties and inspection of the seed, production field, seed processing, seed
treatment, testing and finally packaging for marketing. Each bag package or container is labeled
to prove that it is part of a certified lot. Labeling the bags is the concrete act of certification and
provides the tangible document of certification to each buyer. Following official and technical
descriptions are made on the tag.

A. Official
1. Name and address of certifying agency
2. Species. type. variety
3. Certification, class, generation
4. Lot -identification and test number
5. Date of expiry

B. Technical
1. Purity test report
2. Germination test report
3. Moisture contents
4. Any related educational information.

XII. Conclusion

        The seed processing technology is becoming highly specialized and takes advantage of
various branches of science and technology. However. a general knowledge about the
principles and practices involved in seed processing is beneficial to farmers.


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