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- The ovule after fertilization develops into
the seed with its coats completely fused together with the developing
ovary wall or pericarp. The rice grain has the following structures.
The Pericarp or Fruit Coat
- The pericarp is made up of distinct layers
of quadrangular cells which forms the epicarp. These cells have
slight thickening and are followed by cells which are much compressed
and form the mesocarp consisting of two to three layers.
- The endocarp is single layer of tube
cells. The colour in the rice grain is found in the pericarp
layer in the mature stage.
Seed Biology
- The ovule after fertilization develops
into the seed with its coats completely fused together with
the developing ovary wall or pericarp. The rice grain has the
following structures.
The Pericarp or Fruit
Coat
- The pericarp is made up of distinct layers
of quadrangular cells which forms the epicarp. These cells have
slight thickening and are followed by cells which are much compressed
and form the mesocarp consisting of two to three layers.
- The endocarp is single layer of tube
cells. The colour in the rice grain is found in the pericarp
layer in the mature stage.
The Seed Coats
- Due to the pressure brought out by the
developing seed on the pericarp, the testa and tegmen become
much pressed down and out of shape. A few layers of such cells
below the pericarp can be diagnosed as the integuments of seed
coats.
Aleurone Layer
- A prominent layer of rectangular cells which
contain protein lies next to the seed cents. This layer is known
as the aleurone layer. This layer in rice is not coloured unlike
in the case of maize.
- It has been observed that in coloured
varieties of rice, the aleurone layer is thicker than in the
white rice varieties. The coarse rice generally have a larger
aleurone layer than the finer rice. It has also been found that
in poor soils, the aleurone layer is thin and improves in thickness
with the fertility of the soil and manure.
The Endosperm
- The entire mass of tissue below the aleurone
layer is made up of cells which contain plenty of starch grains
and these form the endosperm.
The Embryo
- The scutellum has
an upper free part which has a flesh projection known as ventral
scale. Below this upper ventral scale and almost at the middle
of the free part there is another out growth which can be called
as the 'inner ventral scale' and this inner ventral scale is
peculiar to rice embryos only.
- On the surface of the embryo this out
growth along with the epiblast forms a continuous covering around
the plumule. The structure between the scutellum and the plumule
is the mesocotyl.
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Types of Seeds
- Local varieties are
nothing but traditional varieties but which are susceptible
to diseases and pests and are having long duration for maturity.
In case of rice - Krishnakatukalu, Basangulu.
High Yielding Varieties
- High yielding varieties are dwarf varieties
and having short duration with resistant to pests and diseases
with maximum yield potential.
Eg: I.R -64, I.R - 36, I.R - 50.
Hybrids
It is also called as micro propagation.
Tissue culture involves several techniques which are
- Anther culture
- Embryo rescue or ovary culture or Embryo
culture.
- Protoplast culture and protoplast fusion.
- Somatic embryogenesis.
- To develop a straight variety or true
to type variety in crop plants, pure line selection method is
adopted. In this method the seeds of pure lines are selected
from homogeneous population of a particular crop and multiplied
in the next season. This multiplication process is conducted
in different co-ordinated centers and performance of the pure
lines is tested. If the performance is good then the state varietal
release committee or central varietal release committee releases
the variety of that particular crop.
- The seed supplied from Agricultural Research
Stations, Department of Agriculture, or A.P. State seed corporation
is not adequate to meet the requirements of the farmers. So
the private seed producers are actively engaged in multiplication
and supply of seed to the farmers. But the cost of seed is some
times high and the quality also is not maintained. Hence, the
farmers are motivated to develop their own seed in respect to
varieties.
- A seed village concept was introduced
and the farmers were encouraged to develop their own seed. In
this process the farmer is supplied with limited quantity of
foundation seed or certified seed by Research stations or A.P
State seed corporation. The farmer will grow variety with the
seed supplied in a limited area with good management practices
of both plant husbandry and plant protection. He is also provided
with information of the characters of the variety like duration,
grain type, the time of panicle initiation etc. He observes
the crop from time to time, and the off-types will be removed
as and when noticed. He maintained a homogenous type of plants
having the varietal characters . while harvesting he eliminates
1 meter crop from all sides of the field to avoid contamination
from other varieties grown in neighbor hood and threshed, separately
with all the care to prevent admixture of other varieties in
threshing floor.
- Like wise care will be taken during storage
to maintain purity. Such seed will be used continuously year
after year for the period of 3 to 4 years. Such seed can also
be spread to the co-farmers interested in that specific Variety.
After 4 years the farmer can again secure foundation seed or
certified seed from the Research station. If it is practiced
by atleast 25% of the farmers there will not be any scarcity
for pure good seed.
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Categories of Seed
- Breeder seed is seed
or vegetative propagating material produced by or under the
direct control of the sponsoring plant breeder. It is the basis
of the first and recurring increase of foundation seed.
Foundation Seed
It is obtained from breeder seed by direct
increase and is the source of registered and or certified seed.
Foundation seed is produced on experimental stations of Agricultural
Universities and Government forms.
Certified Seeds
- Certified seed is
produced from foundation or registered seed. It is so known
because it is certified by a seed certifying agency.
- The certified seed is annually produced
by progressive farmers according to standard seed production
practices. Certified seed is available for general distribution
to farmers for commercial crop production.
Public Hybrid
- The hybrids developed by Govt. agencies
or Govt. Institutions and Agricultural Universities are called
public hybrids.
F1 Hybrid
- The resultant seed obtained from crossing
of two genetically dissimilar parents is called F1 Hybrids.
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- Seed viability is defined as " The
capability of a seed to show living properties like germination
and growth". Or
- It is represented by germination percentage
which expresses the number of seedlings that can be produced
by a given number of seeds.
- The duration of seed viability of rice
varieties depends mainly on the following aspects.
- Seed moisture % at the time of storage
( 10 to 12% is desirable).
- Storage conditions.
- Weather conditions ( relative humidity,
rainfall)
Seed Moisture
- The formation of germination
inhibitors was accelerated under reduced oxygen tension and
thereby the water content of the seed is increased which deteriorates
viability.
Storage
- The embryos and endosperm of seeds of
different ages were found to respire, the rate being higher
in fresh seeds then in older ones. Thus, the old seeds are living
but failed to germinate.
- The germination and viability of the
rice seed are related to the formation of inhibitors during
storage.
Weather Conditions
- Higher relative humidity and rainfall
during the storage periods will deteriorate the seed viability
.
- The paddy seed viability depends on the
weather conditions. The seed viability deteriorate very fast
during monsoon season.
- Due to this, the seed harvested during
rabi season do not retain its viability upto the next rabi season,
because it passes through the monsoon weather conditions i.e.,
from June to October months, where as the kharif harvested seed
retains its viability till the next kharif season.
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- Seed dormancy refers
to the resting stage of embryo with low germinability of viable
and freshly harvested grains. It is also defined as inability
or failure of perfectly matured seed to germinate even when
placed under conditions favourable for germination.
- Seed dormancy is an
important varietal trait in tropical rice where rain fall and
high humidity are of frequent occurance during the maturity
and harvest periods. Without dormancy, seed would germinate
on the standing crop.
Classification of Dormancy
Seed Dormancy at Maturity
Stage
- Strong seed dormancy
at maturity of the crop is a most desirable trait for all the
kharif varieties. Some of the rice varieties ( Masuri, I.R -50)
have little or no seed dormancy and in periods of wet weather
at harvest time, the seed may germinate on the panicle itself.
Duration or Length
of Dormancy
- This refers to the period from harvest time
to the time when the seeds have broken their dormancy.
Intensity of Dormancy
- This refers to the
level of breaking dormancy by artificial means, i.e., based
on the germination percentage after heat treatment for four
days at 50 degrees centigrade, and the rice varieties classified
based on germination percentage as follows
Strongly Dormant
- Varieties in which 50% of dormancy is broken
after 4 days of heat treatment.
Moderately Dormant
- Varieties in which 50 to 79% of dormancy is
broken after 4 days of heat treatment.
Weakly Dormant
- Varieties in which
above 80% of dormancy is broken after 4 days of heat treatment.
Factors Influencing
Dormancy Period
Climatic Conditions
Temperature
- Rice produced during
the cloudy wet season ( kharif) has a strong dormancy and longer
duration of dormancy than that of produced during the summer
dry season ( rabi).
- This is mainly due
to the temperature differences ( higher temperatures in rabi)
during the ripening stage of the crop.
Relative Humidity
- Higher R.H in atmosphere
at maturity stage also increase the degree of dormancy.
Age of Seeds
- A wide variation in maturity of seeds can be
observed within a hill, i.e., between the mother tiller to tertiary
tillers. Similarly there is about 7 to 10 days difference in
the maturity of individual seeds within the same panicle.
- The seeds in the upper portion of the panicle
have earlier maturity than the lower portion of the panicle.
So the duration, the dormancy of the individual seed varies
with in the hill and also within the panicle.
Genetics of Dormancy
- Genetically dormancy
is dominant over non-dormancy. Dormancy is inherited independently
and can combine with early maturity, photo sensitivity and also
with a range of grain types.
Mechanism of Dormancy
- Dormancy is the resultant
of the slowing down effect of the metabolic process during seed
maturation and also by the slow oxidation of the hormone IAA
( Indole Acetic Acid).
- Hence, it is essential that any treatment aimed
at breaking seed dormancy should hasten the rate of oxidation.
Respiration is a strong competitor for the oxygen available
for the dormancy breaking reaction.
Breaking Seed Dormancy
- Among the several methods available the most
suitable method to break seed dormancy at farmers level is nitric
acid treatment. - Soaking the seed in o.1 N nitric acid i.e.,
6.3 ml per lit. of water for 12 to 24 hours effectively breaks
the seed dormancy, where as the varieties like MTU-1001 which
is having 8 weeks and above dormancy duration should be treated
with higher nitric acid concentration i.e., 10ml per lit. of
water.
- The seeds can be utilized for sowing immediately
after the treatment or they can be dried thoroughly and can
be utilized later for sowing.
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- Seed treatment refers
to the application of fungicide, insecticide or a combination
of both to seeds, such as to disinfect and disinfest them from
seed-borne or soil-borne pathogenic organisms and crop pests
both in field and in storage. It also refers to the subjecting
of seeds to solar energy exposure, immersion in conditioned
water etc.
Benefits of Seed Treatment
- Prevention of spread
of plant diseases.
- Seed treatment protects
seed from seed rot and seedling blight.
- Improves germination.
- Provides protection
from insect pests.
- Controlling soil insects.
Seed Treatment for Breaking
Dormancy (Physiological Dormancy)
Dry Storage
- For species where dormancy is naturally of
short duration, it is often sufficient to store the samples
in a dry place for a short period.
Pre-Chilling
- The replicates for germination are placed in
contact with the moist substratum and kept at low temperature
for an initial period. Agricultural and vegetable seeds are
kept at a temperature between 5 and 10 degrees Centigrade for
an initial period of upto 7 days. In some cases it may be necessary
to extend the pre-chilling period or to re-chilling.
Pre-Heating
- The replicates for germination should be heated
at a temperature not exceeding 40 degree C, with free air circulation,
for a period of upto 7 days before they are placed under the
prescribed germination conditions.
Light
- The test should be illuminated during atleast
8 hours in every twenty four hours cycle and during the high
temperature period when the seeds are germinated at alternating
temperatures. The light intensity should be approximately 750
- 1250 lux from cool white lamps. Illumination is recommended
especially for certain tropical and sub-tropical grasses.
Eg. Chloris gayana, Cynodon
Potassium Nitrate (
KNo3)
- The germination substratum may be maintained
with 0.2% solution of KNo3. It effectively break the seed dormancy.
Gibberellic Acid( GA3)
- This GA3 method is recommended for wheat, oat
etc.
Sealed Polythene Envelops
- When a high proportion of fresh un-germinated
seeds are found at the end of the standard test, then re-test
in a sealed polythene envelop of sufficient size will usually
induce these seeds to germinate.
- In case of rice among the several methods for
breaking dormancy are available the most suitable method at
farmers level is nitric acid treatment.
- Soaking the seed in 0.1 N nitric acid i.e.,
6.3 ml per lit. of water for 12 to 24 hours effectively break
the seed dormancy, where as the varieties like MTU-1001 which
is having 8 weeks and above dormancy duration should be treated
with higher nitric acid concentration i.e., 10ml per lit. of
water.
- The seed can be utilized for sowing immediately
after the treatment or they can be dried thoroughly and can
be utilized later for sowing.
Seed Treatment for
Protection Against Pests and Diseases
- Several insecticides and fungicides are used
in seed treatment to protect the seeds from pests and diseases.
These may be merchandized in combination or individual. In case
of paddy the seed is treated with carbendism @ 1 gm / Kg of
seed to protect against plant diseases.
- The seedling dip in chlorpyriphos 2.5 EC solution
@ 1ml /lit of water was suggested to protect against insect
pests like rice stem borer, BPH etc.
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- Seed germination is
the resumption of growth by the embryo and development of young
plant from the seed.
- Germination, in a
laboratory test, is the emergence and development from the seed
embryo of those essential structures which, for the kind of
being tested, indicate the ability to develop into a normal
plant under favourable conditions in the soil.
Treatments for Promoting
Germination
- For reasons such as
physiological dormancy, hard seededness, inhibitory substances
a considerable number of hard or fresh seeds may remain at the
end of the germination test.
- When a proportion
of fresh or dormant seeds remain at the end of the test period,
complete germination can often be obtained by re-testing after
a period of dry storage. The following methods may also be used
to induce germination.
Methods to Overcome Physiological Dormancy
- Dry storage
- Pre-chilling
- Pre-heating
- Light treatment
- Potassium nitrate
( KNo3) treatment
- Gibberellic acid (GA3)
treatment
- Sealed polythene envelope treatment.
Methods of Removing
Inhibitory Substances
- Pre - washing
- Removal of structures
around the seed.
- Disinfection of the seed.
Methods for Removing
Hard Seededness
- Soaking
- Mechanical scarification
- Acid scarification.
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- The purpose of seed
storage is to maintain the seed in good physical and physiological
condition from the time they are harvested until the time they
are planted.
Stages of Seed Storage
- The seeds are considered
to be in storage from the moment they reach physiological maturity
until they germinate or until they are thrown away because they
are dead or otherwise worthless.
- The entire storage
period can be conveniently divided into following stages.
- Storage on plants
( physiological maturity until harvest).
- Harvest, until processed
and stored in a warehouse.
- In - storage ( warehouses)
- In transit ( Railway
wagons, trucks, carts, railway sheds etc.).
- In retail stores.
- On the user's farm.
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Why Quality Seed Production?
- Because:
- Most Important Agricultural
Input for a Farmers
- For Increased Grain
Yield
- High Product Quality
- Specific requirement
- Business for companies
- Employment to rural
people
- Backbone of nation’s economy
Sources Of Seeds
- Nucleus Seed- From Breeder of Hybrid /Variety
of Proprietor Breeder
- Breeder Seed - From Breeder of Hybrid /Variety
of Proprietor Breeder
- Foundation Seed-From Breeder Seed
- Certified/Truthful Seed- From Foundation Seed.
Nucleus Seed /Breeder
Seed à Foundation Seed Stage I/Stage-II –
Certified/Truthful Seed– Commercial grain for farmer’s
consumption
Seed Production Planning
MOTTO: Plan every thing before starting
Requirements for Quality
seed production facilities
MOTTO: Purity of Foundation
will ensure minimum efforts in field for production of high
quality seed
- High purity of breeder
seed.
- For in-house hybrids
Inspection of Breeder Seed plot by team of other breeders to
produce best quality breeder seed.
- For in-house foundation
seed of proprietary hybrids involvement of concerned Breeder
with F/S production official.
- High Quality foundation
seed minimizes the efforts for quality seed production.
- Plan the production
of foundation Seed three years in advance before the actual
marketing of Seed.
- Inspection of F/S plots by concern Breeders
to ensure best quality
Seed Production
MOTTO: Dedicated Team
work with Quality consciousness
- Selection of reliable growers before start
of season
- Growers should be knowledgeable,financially
sound and willing to take extra efforts to take up seed production
operations
- Seed production meeting before start of season
for allocation of area to different production areas
- Development of new production areas
- Regular field inspections by seed production
team at different stages of crop growth to advise growers on
different operations
- Random Field inspections by Seed Quality Field
Team to monitor the various seed production operations
- Midseason review of seed production to go for
alternate area if falling short of targets.
- Group and mass Seed Field inspections by seed
production team at critical stages of crop growth in crucial
- highly cross pollinated crops like Pearl millet,
maize sunflower and Jowar
- Harvesting and threshing instructions to growers
to avoid admixtures.
- Other important operations / instructions as
per crop growth
Seed Processing Plant
Operations
MOTTO: Quality of processed
seed should reflect on Market
- Most important function after seed production
- Overhauling and servicing of plant Machinery
before start of season. Replace worn-out parts. Keep spares
for emergencies. Extra Important implements to be kept in godown.
- Trained operators of plant machinery
- Separate godown for incoming, processed, sales
return and ruminant seed.
- Co-ordination with seed health team for sampling,
dispatches and movement of Seed
- Proper up storage and placement of screens,
- Proper records of processed, remnant and processing
losses to build full faith of seed grower in company
- Record of seed arrival, dispatch and sales
returns
Seed Health Laboratory
MOTTO: To ensure that
only and only quality seed reaches the growers .
- All facilities for testing of seed produced
- To ensure that every lot of seed is tested
for all the quality parameters of seed health before the dispatch
of seed.
- Trained qualified officicial for sampling of
seed during processing of seed lots
- Testing of all seed lots for germination, seed
vigor, infestations and purity etc
- Confidentiality of seed sampling and testing
process
- Seed health laboratory person to be trained
in such a way that he catches the problems of seed even visually
and to be very careful while testing these suspected lots for
seed health.
Grow out tests (GOT)
MOTTO: To Test the
Genetic purity of each and every seed lot
- Allocation of area before the season to create
all the facility required.
- As no. of lots are known before the arrival
of samples hence infra structure should be kept ready before
testing season (maximum Kharif)
- Highly technical qualified staff for the Grow
out Tests.
- Regular institutional Training of staff to
update their knowledge
- All seed lots of hybrids, parental lines and
in-house varieties are to be tested through grow out tests.(GOT)
- To strictly adhere to the plant characters
of hybrids and varieties/lines
- while taking the plant purity observations.
- In high value crop seeds like sunflower and
vegetable hybrids the Finger Printing technology to be used
to check the Genetic purity of seed.
- In case of crops where the time gap between
seed arrival and dispatch is very less the finger printing has
to be adopted to avoid any problem in field.
- Do not look at short term gains while dispatching
of seed at the times of Urgency of seed to market.
Handling of Seed complaints
Motto: Find the root
cause of problem and rectify it immediately.
- Mechanism to check the authenticity of seed
complaints
- Special cell to deal with seed complaints through
marketing network.
- To keep records of history of all seed lots
to be kept to trace the reasons for complaints.
Find the reason for the complaints
- If the faults found in production/processing/Grow
out tests, mechanism to address those problems
Handling of Seed Seed
law Enforcement Agencies
Motto: Hassle free
marketing of seeds
To Deal with Seed law Enforcement agencies (Agric. Department
and Court cases seed failures and consumers forum cases):
- Separate person to deal with court cases
- To keep the records ofall seed lots.
- Knowledge of seed laws to ensure there no convictions.
- Collection of judgments by various courts in
country
- Court cases can be handled easily with experience
of system.
- Not to accept faults in courts in seed failures
but to fight it out
Seed Logistics
Motto: Placement of
seed at market in time, safely with least costs in minimum time
- Selection of good reliable transporters through
tendering process required for bringing the raw seed from field
and dispatch of packed seed in bulk.
- For the small packings dispatches selection
of transporters with maximum reach to destinations
- Emphasis on cost reduction through proper planning
of dispatches.
- Safe movement of material by sending through
quality vehicles with full protection
- Use of railways instead of road transport for
bulk transportation and small important seeds to far off locations
- Monitoring of movement of seed till it reaches
the destination.
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Seed Biology 