saving your own vegetable seeds part i · modes of pollination self-pollination –pollen grains...
TRANSCRIPT
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1
Saving Your Own Vegetable Seeds
Part I
AVRDC – The World Vegetable Center
Global Technology Dissemination
Wuu-Yang (Willie) Chen
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Outline
• Reproduction of plants
• How to produce and harvest seeds
• Hands-on practicum
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Modes of Reproduction in Plants
• Sexual reproduction
– Involves male (pollen) & female (egg) flowers
– Pollination produces seeds which grow into new plants
– Ex. tomato, pepper
• Vegetative reproduction
– Sex (flowers) is not involved
– New plants develop from a portion of plant body
– Ex. sweet potato, banana
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Types of Planting Materials
• Seeds
– Dry seeds
– Wet seeds with mucilaginous coating
– Wet seeds without mucilaginous coating
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Types of Planting Materials
• Cuttings
–50-100 cm stem
–Upper 20-30 cm terminals
–Survives better when older leaves are trimmed
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Types of Planting Materials
• Rhizomes/Corms
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Types of Planting Materials
• Bulbs/Tubers
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How to Save Vegetable Seeds
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Selection Criteria
• Traits subject to selection
– Seedling color
– Leaf shape, size
– Disease susceptibility
– Insect pest tolerance
– Flowering time
– Pollen fertility
– Plant habit
– Fruit shape, color, size
– Earliness of fruit maturity
– Taste, texture
– Yield
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Selection Strategies
• Negative selection (remove off-types due to mutation, out crossing, segregation) – Roguing
• Positive selection– Bulk (mass) selection (bulk at least 30 plants)
– Half sib selection:• Select individual plants, save seed separately
• Grow out in rows
• Bulk seed only from rows with acceptable overall performance
– Progeny testing
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Selection Strategies
• Negative selection (remove off-types due to mutation, out crossing, segregation)
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Measure Moisture Content
• Carefully weigh a sample of seed (Wb)
• Dry at 100-120oC for several hours
• Weigh sample again (Wa): weight lost is
moisture
• % moisture = X 100%Wb – Wa
Wb
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Parts of a Perfect Flower
Female
repro-
ductive
organ:
pistil
(stigma,
style, ovary)
Male repro-
ductive
organ:
stamen
(anther, fila-
ment)
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Producing New Seeds Through Pollination:
Basic Steps
• Anther releases pollen
• Pollen lands on stigma
• Pollen grows down the style to the ovary
• Pollen fertilizes an ovule to form a zygote
(new individual)
• Seed maturation
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Producing New Seeds Through Pollination
3 Pollen
tube
grows
2 Pollen
lands on
stigma
1 Anther
releases
pollen
4 Sperm
fertilizes
egg
5 Seeds
develop
over
time
http://www.emunix.emich.edu/~ghannan/systbot/doublefertanimation.html
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Modes of Pollination
Self-pollination
– Pollen grains from anther of a given plant fall on
the stigma of the same flower (perfect flower)
– Pollen grains from a flower of one plant fall on the
stigmas of other flowers of the same plant
Cross-pollination
– Pollen grains from a flower of one plant fall on the
stigmas of flowers of another plant
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Can you identify the Capsicum flower parts on
the left using the diagram on the right?
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Can you identify the eggplant flower parts
on the left using the diagram on the right?
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Some Vegetable Crops Have Separate Female and
Male Flowers – example, squash
Female Male Induced pollination
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What are Open-Pollinated Varieties?
• Crop can be self-pollinated or cross-
pollinated.
• Plants are allowed to pollinate freely, and
seed can be harvested from all plants.
• Farmers can keep the seeds for next
cropping season.
Can you keep seeds of hybrids for next
cropping season?
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How to Keep Seed Pure
• Isolation in distance
• Bagging
• Caging
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Isolation Distance
• Separation from similar crops minimizes
– Cross pollination by airborne pollen, insects
– Risk of physical admixture
– Recommended distance varies with crop, surrounding vegetation, wind patterns,
– Time isolation may also be possible
(H. Van de Berg, 2004. Small-scale seed production, Agrodok,
©Agromisa Foundation, Wageningen, 2004.)
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Avoid Admixture
• Keep all containers thoroughly clean
• Keep work area and tools cleanded, swept
• Label or mark all containers with cultivar
name and harvest date, etc.
• Store different varieties separately
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Recommended Isolation Distances for
Seed Production
• 50 meters (self pollinated; avoid physical mixing)
– Bean, chicory, endive, Lettuce, Pea, Tomato
• 200 + meters (insect borne pollen):
– Asparagus, Cabbage and brassicas, Carrot, Celery,
cucumber, Eggplant, Melons, Onion Parsley,
Pepper , Squash
• 2 km or more (airborne pollen)
– Beet, Corn, Spinach, Swiss Chard
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Vegetables Needing Vernalization to
Produce Seed Stalks
• Beet
• Brussels Sprouts
• Cabbage
• Carrot
• Celery
• Chard, swiss
• Collard
• Florence Fennel
• Kale
• Leek
• Onion
• Parsley
• Parsnip
• Radish (winter type)
• Rutabega
• Turnip
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Seed Drying
• Reduce moisture gently, by air flow under sun
• Low heat dryer (max. 45-50oC)
• Dessicant in air-tite container (e.g. calcium chloride in glass jar)-keep physically separated from seed
• Seed will reach equilibrium with atmosphere in a few weeks
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Seed Quality Factors
• Moisture content
• Cleanliness (purity)
– Dirt, debris
– Weed Seed
• Viability and Vigor
• Seed Health
– Seed borne pathogens
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Seed Quality
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Storing Seeds
• Humidity
• Darkness
• Temperature
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Seed Storage Environment
“the sum of the percentage relative humidity
plus the temperature in degrees
Fahrenheit should not exceed
100.”(Harrington, 1972)
RH(%) + T(⁰F) ≤ 100
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Vapor Proof Packaging
• Cans, glass, foil packs can maintain moisture equilibrium at varying temperatures
• Seeds need to be dried to lower moisture content before sealing
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Seed Storage Room or Cabinets
• Heavily insulated
• Good temperature and humidity control – Target maintaining seed at < 8% moisture content
• Temperature (oF) + Relative Humidity (%RH) ≤100
• Seed life doubled for each 1% reduction in moisture content (between 6 and 16%)
• Seed life halved for each 5oC increase in temperature (between 0 and 50oC)
– Cooling, dehumidification, monitoring circuits
• Volume capacity needed will grow over time.
• Moisture-proof containers will help, if seed is initially dried to low moisture contents
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Evaluation of Germination Test
• If you are saving seed to grow next year, it
is important to know that they will sprout
when you want them to.
• Whether it is seed you saved, or those
received from a gardening friend, make
sure to do a germination test sometime
before planting.
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Germination
• Germination is defined as:
– "the emergence and development from the seed
embryo of those essential structures which are
indicative of the ability to produce a normal plant
under favorable conditions."
• The purpose of laboratory testing of seed
germination are:
– to assess seed quality or viability
– to predict performance of the seed and seedling in the
field
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Top of Pepper Method
• Procedure:
1. Place water absorbent material inside the waterproof tray
2. Wet the water absorbent material and allow free water to
drip off for a minute.
3. Count out 20 seeds from each sample and place them on
absorbent material inside the tray
4. Record the number of germinated seeds
5. Compute germination test for 5 days and for 10 days
• Note:
– The size sample depends on the size of the seed lot but
usually 20 to 100 seeds are germinated.
– Each day check that absorbent material remains moist.
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Germination Rate Test
• Cabbage as an example
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1 day 3 day2 day
4 day 5 day 6 day
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Calculating the Germination Rate
• Germination rate is the average number of
seeds that germinate over the five and ten
day periods.
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Germination (%) = x 100Number of seeds germinated
Number of seeds on tray
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Tomato
• Production:
– Grow best in dry season
– Day 21-25oC, night 15-20oC
– Avoid field where the previous crop was
tomato; this prevents the new seed crop
from being contaminated with seeds from
volunteer tomato plants
– Growing tomato after paddy rice reduces
the incidence of diseases and nematodes
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Tomato
• Isolation:
– Usually not needed
– Perfect, self-pollinating flowers
• Selection:
– Look for early maturing and attractive
plants
– Resistance to disease
• Harvesting:
– Allow tomatoes to completely ripen on the
plant before harvesting for seed
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Tomato
• Processing: (Video)
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Fermentation
25-30oC
for 2-3 days
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Hands-on Practicum
• Germination test
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Hands-on Practicum
• Tomato seeds extraction (I)
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