SEED PROCESSING: MANAGEMENT TECHNIQUES

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SEED PROCESSING AND
MANAGEMENT TECHNIQUES

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Contents

• ?.Seed processing content
• 1.Seed cleaning
• 2. Seed moisture testing
• 3. Seed drying
• 4. Seed viability testing
• 5. Seed health testing
• ?.Management techniques
• ?.HACCP Quality management system

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?.Seed processing content

• Seed processing involves cleaning the seed
  samples of extraneous materials, drying them to
  optimum moisture levels, testing their
  germination and packaging them in appropriate
  containers for conservation and distribution.

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1.Seed cleaning

• The cost of maintaining an accession in a
  genebank is high and space is limited. Debris and
  damaged seeds can spread infection. Therefore,
  place only good quality viable seeds in storage.
• Seed cleaning involves removal of debris, low
  quality, infested or infected seeds and seeds of
  different species (weeds).

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2. Seed moisture testing

• Methods prescribed by the International Seed
  Testing Association (ISTA) are used for
  determining the seed moisture content in
  genebanks.

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• ISTA has prescribed two kinds of oven-drying
  methods for determining moisture content
• Low-constant temperature oven method for
  groundnut (oily seeds).
• High-constant temperature oven method for
  sorghum, millets, chickpea and pigeonpea
  (non-oily seeds).
• Grinding is required for determination of
  moisture content in all ICRISAT mandate crops,
  except millets.

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Equipment used to determine seed moisture content
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3. Seed drying

• (1)Dehumidified drying
• (2)Silica gel drying

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• Seed-drying cabinet at ICRISAT genebank.

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Walk-in seed drying room at
ICRISAT genebank
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Seed drying using silica gel at
ICRISAT genebank.
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4. Seed viability testing

• (1)Germination test
• Complete germination can be achieved only
  under optimum conditions of light, temperature
  and water. The requirements for germination vary
  with species as shown in Table.

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• Recommended conditions for germinating seeds of
  ICRISAT mandate crops.

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• Two methods are used for testing germination
• A. Top of paper method for millets.
• B. Between paper (Rolled towel) method for
  sorghum, chickpea, pigeonpea and groundnut.
• Paper towel is used as substrate for germination
  in both these methods.

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A. Top of paper method

• Quality of paper towel
• The paper used as substrate should not be toxic
  to developing seedlings.
• It should be able to absorb and supply
  sufficient moisture to the seeds to germinate.
• It should be strong enough not to fall apart
  when handled and not to be penetrated by the
  roots of developing seedlings.

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Top of paper method

• Place the paper in 9-cm petri dishes.
• Moisten it with about 4 ml of distilled water.
• Put a label in the petri dish with accession
  number, number of replicate and date of the test.
• Spread the seeds at regular distance on the
  surface of the paper.
• Cover the petri dishes and keep them in a
  plastic bag to prevent drying.
• Place the petri dishes in an incubator
  maintained at the recommended optimum temperature.

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Testing germination of seeds on the top of filter
paper.
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2
3
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B. Between paper (Rolled towel) method

• Cut the paper to a convenient size to hold one
  replicate of the seeds (1).
• Label the paper on the outside at one end with
  the accession number, replicate number and the
  date of testing (2).
• Moisten the paper towels with water.
• Arrange the seeds in rows at regular intervals
  4 cm from the top edge, leaving 34 cm gap on the
  sides (3).

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• Cover the seeds with another sheet of dry paper
  towel (4).
• Roll the paper loosely from the label end (5).
• Put a paper clip to hold the rolled paper
  towels from falling apart (6).
• Keep the rolls in a plastic tray (7).
• Add sufficient quantity of distilled water
  (covering the bottom 3-cm of rolls) to the tray.
• Place the tray in an incubator maintained at
  recommended temperature.

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Test germination of seeds of between moist paper
towels.
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Trays containing rolled paper towels placed in an
incubator.
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C. Evaluation of germination tests

• Seedlings with the following defects are
  classified as abnormal
• Roots
• primary root stunted, stubby, missing,
  broken, split from the tip, spindly, trapped in
  the seed coat, with negative geotropism, glassy,
  decayed due to primary infection, and with less
  than two secondary roots.

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• Shoot (hypocotyl, epicotyl and mesocotyl)
• short and thick, split right through, missing,
  constricted, twisted, glassy, and decayed due to
  primary infection.
• Terminal bud/leaves
• deformed, damaged, missing, and decayed due to
  primary infection
• Cotyledons
• swollen, deformed, necrotic, glassy, separated
  or missing, and decayed due to primary infection

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a
b
Normal and abnormal seedlings of sorghum (a) and
pearl millet (b).
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a
b
c
Normal (left) and abnormal (right) seedlings in
chickpea (a), pigeonpea (b) and groundnut (c).
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• (2) Topographical tetrazolium test for
  viability
• The tetrazolium test can be used as a
  backup procedure to germination tests in
  genebanks.
• It can be applied to firm seeds,
  which have failed to germinate at the end of
  germination test.

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• The tetrazolium test procedure includes the
  following steps
• Preconditioning
• Remove the seed covering structures (glumes,
  etc).
• Precondition the seeds by first soaking in
  water or by placing them on a moist medium at
  30C.

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• Staining
• Bisect the seeds longitudinally through the
  embryo with a razor blade.
• Discard one-half of the seed and place the
  other half in the staining solution at
  recommended concentration (Table 4D.2.1) in a
  glass vial.
• Place the vials in an incubator maintained in
  the dark at recommended temperatures and duration
  (Table 4D.2.1).

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• After staining, wash the seeds several times in
  distilled water to remove excess stain.
• Immerse the seeds in lactophenol (1 L of
  lactophenol prepared from 200 ml phenol, 200 ml
  lactic acid, 400 ml glycerine, and 200 ml water)
  solution for 12 h before evaluation of the
  seeds.
• Evaluate the seeds for staining pattern under a
  low power binocular microscope.
• Viable tissues stain bright red. Pink and very
  dark red stains are indicative of dead tissue.

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• Classify the seeds into three categories
  depending on staining pattern
• completely stained and viable seeds,
• completely unstained seeds that are
  nonviable, and
• partially stained seeds.

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• (3)Seed vigor tests
• Vigor is the sum total of all those properties
  in seed which upon sowing result in rapid and
  uniform production of healthy seedlings under a
  wide range of environments, including both
  favorable and stress conditions. Vigor tests
  supplement information about seed quality.

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Selected tests for vigor

• Speed of germination
• Speed of germination is an important measure
  of vigor. It depends on the time taken to reach
  50 germination at constant temperature. Seeds
  with low vigor take longer time to germinate.
• Place 2550 seeds over filter paper (Whatman
  No. 1) moistened with 4 ml distilled water inside
  a petri dish.
• Count and remove the germinated seeds every 12
  h. Germination is considered to have occurred
  when the radicle protrudes by 24 mm.
• Calculate germination index using the equation
  S(t n)/Sn, where n is the number of germinated
  seeds and t is the number of hours from the
  beginning of the germination test.

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• Seedling growth test
• Measurements of seedling growth (root and
  shoot) at specific number of days after sowing
  give an indication of their vigor (Annexure
  4D.3.1). Slow seedling growth (shorter roots and
  shoots) indicates low vigor.
• Conduct the germination test as described
  earlier and measure the length of the root and
  shoot.
• The seedlings may be cut and dried at 110C for
  17 h to record their dry weights, which is more
  for better quality seeds.

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• Membrane integrity
• The test is based on measuring the
  concentration of leachates by electrical
  conductivity (Annexure 4D.3.1). Lowvigor seeds
  generally possess poor membrane structure. When
  such seeds are soaked in water, greater
  electrolyte loss occurs, leading to higher
  conductivity of water. The test is mainly used
  for grain legumes.
• Soak 10 seeds in 50 ml of distilled water in a
  beaker at room temperature.
• Measure leachate conductivity after 24 h using
  a digital conductivity bridge.
• Record the reading in µS ml-1 water g-1 dry
  weight of the seed sample.
• A lower reading indicates seeds with higher
  vigor and vice versa. It is important to note
  that many species (eg, legumes) have seeds that
  are impermeable or only slowly permeable to
  water. This can affect the leaching of
  electrolytes from seeds in a conductivity test.

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5. Seed health testing

• Seed borne fungi such as Alternaria, Fusarium,
  Penicillium, Aspergillus and Rhizopus spp. affect
  longevity during storage. Curators should ensure
  that seeds prepared for long-term conservation
  are free from the seed borne pathogens. The
  methods employed to detect the pathogens are
  referred to as seed health testing methods.

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• (1) Visual examination
• Seeds are examined under an illuminated
  magnifying lens (2) or under lowpower
  stereobinocular microscope (Fig. 4E.1.1). By
  this method, it is possible to detect sclerotia,
  smut balls, fungal spores and other
  fructifications such as pycnidia, perithecia,
  etc.

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Seed health testing in laboratory using binocular
microscope.
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• (2)Blotter test
• Blotter tests are similar to germination tests
  in that seeds are placed on moistened layers of
  blotter paper and incubated under conditions that
  promote fungal growth.

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• Line the lower lid of the petri dishes with
  three layers of blotter paper moistened with
  sterile water.
• Drain off excess water and place 2025 seeds
  manually with a forceps.
• Evenly space the seeds to avoid contact with
  each other.
• Incubate the seeds under near ultraviolet light
  in alternating cycles of 12-h light/darkness for
  7 days at 20 2C.
• Examine the petri dishes under a
  stereo-binocular microscope for fungi developing
  on the seeds.
• Profuse seedling growth may make
  interpretations difficult. This may be overcome
  by adding 2,4-D sodium salt to provide a 0.2
  moistening solution.

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• (3)Agar plate method
• This is the most common method used for
  identification of seed borne fungi.
• Prepare the medium by mixing Potato Dextrose
  Agar (PDA) powder with appropriate quantity of
  water.
• Sterilize the mixture in an autoclave at 121C
  for 1520 minutes with 15 lb pressure and cool to
  about 50C.
• Carefully pour the mixture into petri dishes by
  lifting the lid enough only to pour in the agar
  to avoid contamination.

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• Allow it to cool and solidify for 20 min.
• Surface-disinfect the seed by pre-treating for
  1 min in a 1 sodium hypochlorite (NaOCl)
  solution prepared by diluting 20 parts of laundry
  bleach (5.25 NaOCl) with 85 parts of water.
• Place about 10 seeds (depending on size) on the
  agar surface with a forceps.
• Incubate the petri dishes at 2025C for about
  58 days.
• Identify the seed borne pathogens on the basis
  of colony and spore characteristics.
• Sometimes, bacterial colonies develop on the
  agar and inhibit fungal growth making
  identification difficult. This can be overcome by
  adding an antibiotic such as streptomycin to the
  autoclaved agar medium after it cools to 5055C.

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• (4)Seed health standard
• Examine each seed for the presence of
  pathogens.
• If the percentage of seeds infected by one or
  more of the following fungi is gt5, the seeds are
  unsuitable for conservation as base collection .

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?. Management techniques

• Management objective
• The basic management objective in a
  seed extractory is the attainment of quality
  seed.Quality is defined as good vigor, high
  purity percent, and germination percent. The
  management process to achieve this objective, or
  any objective, may be separated into five parts
  PLANNING, ORGANIZATION, MOTIVATION, CONTROL, AND
  INNOVATION (Batten 1969). Each part is dependent
  upon the other. Seed extraction easily fits into
  these five areas.

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Planning

• By the extraction year a fair estimate
  of crop size should be available to the manager.
  With this information it is then possible to plan
  budgeting data cost,length of time to accomplish
  the job, size of crew, equipment needs, and
  contingencies.These items are the very least
  required of a good extraction plan.

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Organization

• Organizing the job is where crew
  deployment takes place. A manager should know the
  people in the crew and how to best deploy them
  i.e., what they are best suited to do.Not all
  crew members function at the same levels. This is
  where skillful managers can best organize the
  utilization of their crew.

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Motivation

• Motivation is a very fragile word. The
  concept is not that difficult to understand.
  Webster defines motivate as some inner drive,
  impulse, intention, et cetera, that causes a
  person to do something or act in a certain way
  incentive, goal.Dwight Eisenhower is quoted as
  saying "Leadership is the ability to get a person
  to do what you want him to do when you want it
  done, in a way you want it done, because he wants
  to do it." I feel this is the core of seed
  extraction management.

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Control

• Control can be obtained in a few ways.
  As a manager you can be in the extractory
  checking on the crew's work constantly, or you
  can establish checks at various points in the
  process. If an accountability system is
  established, the spot check works rather well.

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Innovation

• In seed extracting this is, and must
  be, an on-going process. There is no single best
  method of cleaning seed. Each seedlot is slightly
  different. The size, weight, and shape of seed
  differs not only between lots but also within
  lots.The crew often times can be the best source
  of new ideas.

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MANAGEMENT METHODS AT COEUR D'ALENE

• The Coeur d'Alene Nursery is as follows
  The Nursery has established minimum purity
  standards for each species which we clean (Table
  1). These standards are made known to each crew
  member before the start of extraction (the
  standards are re-evaluated each year to reflect
  the state of the art). In doing this I accomplish
  two points

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• (1) Management objectives are
  explained to the crew, and (2) A quantitative
  goal is presented. It is also explained that when
  each new seedlot is tested for purity and falls
  below the standard, it will be tagged with yellow
  flagging and must be recleaned. This, coupled
  with the fact that as a seedlot is processed from
  tumblers to scalper to dewinger to fanning mill
  to pneumatic separator, the operators of each
  piece of equipment sign off on the lot,instills
  quite a bit of pride in work as well as a sense
  of accomplishment. When the system was first
  instituted on those few lots that needed further
  processing, crew members took it as a personal
  affront to receive a yellow flag. That's a nice
  type of management problem to deal with.

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Table l.--Minimum purity standards, Coeur d'Alene
Nursery
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• How does our crew accomplish the task
  of cleaning seed to a predetermined purity? The
  obvious answer is training and communication.
  This does not mean providing information. Often
  managers tend to equate information with
  understanding. This can lead to problems.
  Managers must communicate for the purpose of
  obtaining a level of understanding by crew
  members (Miller and Steinberg 1975). In 1978 the
  Coeur d'Alene Nursery processed 14M bushels of
  cones yielding 10M pounds of seed. This was
  accomplished with a neophyte crew. They had never
  cleaned seed before.

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• Each piece of equipment was
  explained as to its function and how it worked.
  Crew members were given instructions as to their
  equipment operations and after a short break in
  period told to clean seed. On those machines with
  different screens, starting points were
  established for each species and crew members
  were told to experiment for themselves to decide
  which other screens would work best, again
  keeping in mind the production goals. This free
  reign further installed a sense of accomplishment
  and pride in work.

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• As notes were compared crew
  members began to agree with my statement that
  each seedlot is different regardless of species,
  and certain standards began to be established as
  starting points for cleaning. Often times they
  were not in agreement with my original
  suggestions. Innovation or new methods to clean
  seed are often brought out by crew members. I
  feel it is important that they are given the
  freedom to try these techniques once they have
  been discussed with management. A successful
  process which we use for pitch removal on western
  larch came about after such a discussion.

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• It was also necessary to explain to
  crew members what to look for in seed cleaning,
  which trash could be removed in certain ways, and
  to explain that while seed cleaning is not hard
  work, it does require patience. One must accept
  each seedlot as a challenge to clean it to a
  certain standard. At Coeur d'Alene the crew
  members also participate in both bareroot and
  container sowing operations and therefore have
  the opportunity to see the fruits of their labors
  or past errors as well as an understanding of
  where they fit in the scheme of things.
  Monitoring is accomplished with an X-Ray unit at
  various points in the process. It is done not to
  criticize the operators of equipment but as an
  instructional tool to help them accomplish
  management's goal of high quality seed.

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?.HACCP Quality management system

• HACCPHazard analysis and critical control point
• Concept
• The hazard analysis and critical
  control point is a guarantee food security
  preventive technology management system. It uses
  food technology, microbiology, chemistry and
  physics, quality control and risk assessment, and
  other aspects of the theory and method, To the
  whole food chain real dangers in the risk
  assessment, and finally find out the quality of
  the final product may impact on the key point,
  and take preventive measures to control the harm
  in before they happen to control, to make the
  food achieve higher levels of security.

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• HACCP quality management system to make steps
• 1). hazard analysis
• 2). Determine key control
• 3). To make sure that each key point of
  critical value
• 4). Sure monitoring program
• 5). Make rectification measures
• 6). Verification Procedures

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Thank you!