1. Genetic principles

1. Genetic principles

    • These principles highly depend on genetic characters of seed which can modify its performance in production programme. In seed production genetic characters are evaluated through genetic purity.
    • Hence following principles are to be considered to obtain true to type seeds.
    a. Seed production in adopted area
    b. Approved seed source and generation system of seed multiplication
    • Seed source should be from authenticated and approved public or private sector agencies. Always use higher class of seed for production of seeds. (eg. breeder for foundation and foundation for certified seed)
    Generation system of seed multiplication
    • Generation system of seed multiplication is nothing but the production of a particular class of seed from specific class of seed up to certified seed stage.
    • The choice of a proper seed multiplication model is the key to further success of a seed programme.
    • This is basically depends upon,
    i. The rate of genetic deterioration
    ii. Seed multiplication ratio and
    iii. Total seed demand
    • Based on these factors different seed multiplication models may be derived for each crop and the seed multiplication agency should decide how quickly the farmers can be supplied with the seed of newly released varieties, after the nucleus seed stock has been handed over to the concerned agency, so that it may replace the old varieties. In view of the basic factors, the chain of seed multiplication models could be,
    (i). THREE Generation model :- Breeder seed - Foundation seed - Certified seed
    (ii). FOUR Generation model Breeder seed :- Foundation seed (I) Foundation seed (II) –Certified seed
    (iii). FIVE Generation model :- Breeder seed - Foundation seed (I) - Foundation seed (II) –Certified seed (I) - Certified seed (II)
    Generation system of seed multiplication and quality control (notified varieties and hybrids)


    Class of seed

    Quality control system

    Concerned breeder
    Sponsoring institution breeding
    Breeder himself (no specified tag)
    Nucleus seed Maintenance
    Concerned breeder or
    Sponsoring institution
    Breeder seed
    (Golden yellow tag)
    Breeder seed
    State department of agrl Foundation seed State seed National
    Seeds corporation
    Certification seed Cooperative and Private sectors (White tag) Field inspection and Central and State seed testing to check minimum required standards of genetic, physical purity
    Farmers Certified Seed
    Truthful labeled seed
    (Azhar blue tag)
    (Opal green)

    • Three Generation model - (BS-FS-CS) - FOR CROSS POLLINATED CROPS
    • Four Generation model - (BS-FSI-FS II-CS) - FOR SELF POLLINATED CROPS
    c. Previous crop requirement
    • This is very much required to avoid volunteer plants which can interrupt with genetic purity. Hence the land selected should not be grown with same crop of other varieties.
    d. Prevention of natural crossing
    • In sexually propagated crops natural crossing is another most important source of genetic contamination. This occurs due to crossing with undesirable plants, diseased plants and off types. This phenomenon is highly applicable to often and cross pollinated crops. The extend of genetic contamination in seed fields due to natural crossing depends upon the breeding system, isolation distance ,varietals mass, pollinating agent, insect activity, wind velocity ,humidity and temperature.
    Table .1: Isolation distance required for the production of foundation and certified seeds of various crops
    Sl. No. Name of group (Crops) Isolation in metres
    Foundation Certified
    1 Cole crops

    Cabbage 1600 1000

    Cauliflower 1600 1000

    Chinese cabbage 1600 1000

    Knol-khol 1600 1000
    2 Fruit Vegetables

    Brinjal 200 100

    Capsicum (chillies) 400 200

    Tomato 50 25

    Okra 400 200
    3 Bulbous vegetables

    Garlic 10 5

    Onion 1000 500
    4 Root vegetables

    Beetroot 1600 800

    Carrot 1000 800

    Radish 1600 1000

    Turnip 1600 1000
    5 Tuber vegetables

    Sweet potato 10 5

    Potato 10 5
    6 Rhizomatous vegetables

    Ginger 10 5

    Turmeric 10 5
    7 Legume vegetables

    Cluster bean 50 25

    Cowpea 50 25

    French bean 50 25

    Indian bean 50 25

    Lima bean 50 25

    Peas 10 5
    8 Leafy vegetables

    Amaranths 400 200

    Beet leaf 1600 1000

    Coriander 800 400

    Fenugreek 50 25

    Lettuce - -

    Spinach 1600 1000
    9 Cucurbits (All crops) 1000 500

    e. Mechanical mixture
    • Seeds should be physically pure ie., free from other crop seeds or other varieties of the same crop. It may often takes place at the time of sowing if more than one variety is sown with the same seed drill and also during post harvest handling of seed. Care on prevention is required as these will affect the genetic purity and also population maintenance.
    f. Vigorous roughing
    • Removal of unwanted, non true to type and diseased plants from the seed field is known as roughing. It should be done throughout the life cycle, but much care has to be given prior to the stage at which they could contaminate the seed crop.
    g. Adoption of quality control system
    • Seed must be produced only on adoption of generation system as recommended by Seeds Act 1966 to avoid genetic deterioration.

Last modified: Wednesday, 20 June 2012, 5:27 AM