Isolation distance refers to the minimum separation required between crop varieties to maintain seed purity. There are three main types of isolation: spatial, temporal, and physical barriers. Spatial isolation involves separating fields by distance, with greater distances required for cross-pollinated crops versus self-pollinated crops. Temporal isolation is achieved by staggering planting dates of different varieties by 15-20 days. Physical barriers use border crops or bags to prevent cross-pollination. Factors like pollination method, pollen viability, disease pressure, and seed class influence isolation distance needs. Techniques like block planting, only collecting central seeds, and using barrier crops can reduce isolation distance requirements.

1. WELCOME

2. Isolation distance and its
importance

3. INTRODUCTION
Isolation distance:
Isolation distance is the minimum separation required
between two or more varieties of the same species for the
purpose of keeping seed pure

4. Types of isolation
Types of Isolation:
• 1. Spatial Isolation
• 2. Temporal Isolation
• 3. Physical barrier

5. 1. Spatial Isolation
The spatial separation required between a seed field and
other sources of genetic and mechanical contamination,
especially between varieties of cross pollination.
•more the extent of out crossing wider the distance.
• higher the class of seed wider the distance. (bs v/s fs).
• in hybrid seed production wider the distance
than that of variety(inbred/pureline).

6. 2. Temporal Isolation
crop of seed production
should be sown early or late by a
margin of 15-20 days than
neighboring fields of same or
other variety to prevent entry of
foreign pollens in the field of
seed production.

7. 3. Physical barrier
in surrounding of
crop of seed production
particularly on bunds crop
of well plant height and
densely planted should be
grown to prevent entry of
foreign pollens in the field
of seed production .

8. 4. Physical isolation
It can be practiced by covering the floral part or
whole plant we can avoid the physical contaminants
into seed field.
ex:- paper bags.

9. Factors affecting isolation distance.
 Pollination behavior of crop.
 Pollinating agent
 Pollen trails
 Wide pollinator
 Designated diseases
 Type of seed production
 Class of the seed

10. Pollination behavior of crop.
plants that primarily self-pollinate require less
isolation distance, while plants that primarily cross-
pollinate require greater distances.

11. Pollination agents
1. pollination.
ABIOTIC POLLINATION
 Wind Pollination:
 Water and Rain Pollination:
BIOTIC POLLINATION (INSECT POLLINATION)
 Domesticated bees (honeybees):
 Bumblebees
 Butterflies:
 Moths:
 Flies
 Wasps

12. Pollen trails
 Pollen viability
 Pollen production capacity
 Pollen mate and
 Time of anthesis

13. Wide pollinator
 Inter varietal crossing
 Intra generic crossing
 Inter generic cossing

14. Designated diseases
Crop Designated disease Causal organism
Wheat Loose smut Ustilago tritici
Sorghum Grain smut or Kernel smut Sphacelotheca sorghii
Mustard Alternaria blight Alternaria sp
Pearl millet
Grain smut
Green ear
Ergot
Tolyposporium penicillariae
Sclerospora graminicola
Claviceps microcephala
Sesame Leaf spot Alternaria sp
Brinjal Little leaf Datura virus 2
Chilies
Anthracnose leaf blight
Leaf blight
Gloesporium piperatum
Alternaria solani
Cucurbits Mosaic Cucumis virus
Cowpea Anthracnose Colletotricum sp
Bhendi Yellow vein mosaic Hibiscus virus 1
Potato
Brown rot
Root knot nematode
Pseudomonas solanacearum
Meloidogyne incognita
Tomato
Early blight
Leaf spot
Alternaria solani
Xanthomonas vesicatoria
It refers to the diseases specified for the certification of seeds and for which certification standards must be
met with.

15. Class of the seed
higher the class of seed wider the distance.
that is breeder seed production requires relatively large
isolation distance compared to foundation seed production
i.e breeder seed> foundation seed> certified seed> elite
seed production.

16. Type of seed production
In hybrid seed production wider the distance
than that of varietal improvement (inbred pureline).

17. Importance
 Isolation prevents unwanted cross-pollination
 It is the primary practice required to keep varieties true to type.
 Isolation begins with an understanding of the distance required to limit or
eliminate chances of cross-pollination between two varieties of the same
species.
 You can manage isolation through several methods:
 by distance,
 by timing of flowering, or
 by containment.
 Isolation by distance is the most reliable method, which involves providing
enough distance between a variety and any sources of contaminating
pollen to ensure that the variety remains true to type.

18. Factors affecting isolation distance for
different crops.
Okra
 By the size of the growing area. In large intensively
cultivated fields, the amount of cross pollination is
smaller than it would be in small fields because the
ratio of pollinators to plants is smaller in large plots
than in small plots.
 In addition, if the fields have been sprayed with agro-
chemicals, the pollinator pressure will be even less, and
the amount of cross-pollination will be
correspondingly lower.

19. TOMATO
(1) wind movement
(2) Variety characteristics such as style length
(3) environmental variables affecting style length
(4) pollinator pressure
(5) isolation distance
(6) biodiversity - presence of other pollen-producing plants in
the area of the seed crop.

20. PEPPER
such as
 Location,
 Time of year,
 Changes in insect populations, and
 Climatic factors.
 Several seed saving guides recommend
isolation distances ranging from “several
feet” to “50 feet”,

21. TECHNIQUES FOR DECREASING THE MINIMUM
ISOLATION DISTANCE
Plant in blocks rather than rows:
 Planting crops in blocks rather than rows decreases
the exposure of crops to foreign pollen.
 A block planting has a much smaller periphery than
a row planting.

22. Collect seed from center of block plantings:
 This technique is an extension of the previous
technique, and takes edge effects into account.
 There usually will be a larger percentage of
pollinators at the edges of a block than in the center
of the block.
 Therefore, the plants in the center of the block are
more likely to produce pure seed than those at the
edges.

23. Collect seed from fruits produced during peak
flowering:
 At low planting densities, the ratio of flowers to
pollinators remains relatively constant.
 As the number of flowers increases toward maximum
blooming, a point may be reached in which the ratio
of flowers to pollinators increases.

24. Use barrier crops:
Barrier crops serve several functions:
 1. They provide a physical barrier for pollinators,
disrupting the line of flight and the line of sight.
 2. They distract pollinators by providing alternative
pollen and nectar sources.

25. Isolate in time (staggered blooming times):
An early variety of crop plant can be planted early
in the season, followed three weeks later by a planting
a late variety crop.

26. SITUATIONS REQUIRING INCREASED
ISOLATION DISTANCE
 Larger population of plants.
 Larger number of varieties.
 High pollinator pressure.
 Variety characteristics (susceptible to out crossing).
 Genetically-modified crop nearby

27. SUMMARY OF ISOLATION DISTANCE FACTORS AND
ADJUSTMENTS
FACTORS HAVING AN EFFECT ON ISOLATION DISTANCE INCREASE OR DECREASE DISTANCE
Plants planted in blocks rather than rows Decrease permissible
Seed collection from center of blocks Decrease permissible
Seed collected only from peak production Decrease permissible
Use of barrier crops Decrease permissible
Use of alternate pollen and nectar sources Decrease permissible
Time isolation (staggered blooming times) Decrease permissible
Large seed crop population size of each variety Increase suggested
Larger number of varieties grown for seed Increase suggested
High pollinator pressure due to apiculture Increase required
High pollinator pressure due to biodiversity Increase required
Organic agricultural practices instead of conventional Increase required
Variety characteristics which favor outcrossing Increase required
Genetically modified crop grown nearby Increase required

28. Crop Distance for Distance for
(m) Foundation seed (m) Certified seed (m)
Self pollinated crops
Rice, Wheat, Ragi, 3 3
Groundnut, Greengram,
Cowpea, Tomato
Cross Pollinated Crops
Maize, Mustered, 400 200
Pearlmillet, 1000 25
Lucerne, 400 100
Suhemp 200 100
Castor 300 150
Sunflower 1000 500
Carrot 1000 800
Onion 1000 400
Cucumber 800 400
Often Cross Pollinated Crop
Pigeonpea 100 50
Cotton 50 30
Sorghum 200 100
Chilli,
Brinjal 200 100
Isolation distance for different crops.

29. Refrences
 http://agropedia.iitk.ac.in/content/isolation-distance-different-crops
 http:// IsolationDistancesVer_1pt5
 https://www.seedsavers.org/isolation-distances
 https://www.carolinafarmstewards.org/wp-
content/uploads/2012/05/IsolationDistancesVer_1pt5.pdf

30. Thank you…..
Presented by
Mahammed faizan
MH2TAG0165
Jr.M.Sc ( hort) in GPB
College of horticulture
mudigere.