Principles of seed production 2.pdf

Principles of seed production 2
Seed Science & Technology
K Vanangamudi
ICAR AIEEA JRF & SRF for PG admissions exams
ICAR NET, ARS & STO (T-6) exams
IBPS – AFO exams
Planting ratio, Border rows, Synchronized flowering, Detasseling, Emasculation and dusting, Supplementary pollination, Genetic contaminants, Grow-out tests in Hybrid seed production

1. SEED SCIENCE &TECHNOLOGY
Principles of Seed Production 2

Dr. K. Vanangamudi
Formerly Dean (Agriculture), TNAU, Coimbatore.
Dean, Adhiparasakthi Agricultural College,
Professor & Head,
Seed Science & Technology, TNAU, Coimbatore.


Agronomic principles Completed in Principles of Seed Production 2
Varietal seed production principles
1. Hybrid seed production
1.1. Planting ratio
 Ratio to be maintained between female and male lines in order to have good amount of
pollen grains for proper pollination and fertilization.
 E.g. Rice - 8:2 to 10:2 (Female : Male)
 Maize – 4:2
 Sunflower hybrid seed production is 4:1.
 Cotton (block system) - female and male are raised in a ratio of 8:1 in separate
blocks not more than 5 m distance. Hybrid seed production is by emasculation and
dusting.

2. 1.2. Border rows
 Seed field should be planted with border rows all the four sides with male parent
seeds to have more pollen source and avoid contamination.
 Number of border rows - 4 to 12


1.3. Synchronized flowering
 Uniformity of flowering between parental lines.
 To achieve uniformity, any one of techniques can be done.
 Staggered sowing
 Withholding irrigation
 Application of urea or DAP

 Staggered sowing
 Adjusting sowing time of parental lines in order to have synchronized
flowering between parental lines for proper seed set.
 Early flowering line should be sown later.

3.  E.g. Sunflower KBSH -1 hybrid seed production; male parent is late flowered by 6
days than the female.
 So, sowing of male line 6-D-1, 6 days earlier than female line ensures
synchronized flowering.
 Rice - exertion of female panicle from boot leaf is a problem.
 Spray GA3 @ 70-75 g/ha twice during flowering time.
 Since GA is cell elongation factor, it aids in exertion of panicle.

1.4. Special techniques for hybrid seed production
 Detasseling: Removal of tassel from the female row in maize.

 Emasculation and dusting: Done at proper time of flowering to have good yield and
also to avoid contamination in cotton.

 Not followed in the case of crops where hybrid is produced by utilizing male sterility
system, e.g. sunflower.
1.5. Supplementary pollination
 To have good seed set.
 Rice: Rope pulling or rod driving.

4.  Sunflower: Rubbing or installation of bee hives.

1.6. Genetic contaminants
 Off types: Deviant of seed plant. Common for varieties and hybrids.
 Pollen shedders: Presence of B line in A line of hybrid seed production. Eg. Rice.
 Pollen Partials – Bajra
 Shedding tassel: Presence of tassel in the female row of maize
 Selfed bolls: Cotton - selfed bolls without emasculation and dusting.
 Selfed fruits: in the case of other vegetables.

1.7. Method of harvest
 Hybrids - harvest R line first, remove produce from field and do one final rouging in
female row and do harvest.
2. Genetic principles
2.1. Maintenance of genetic purity during seed production
 Various steps suggested by Home (1953), to maintain varietal purity
 Use of approved seed
 Inspection and approval of fields prior to planting.
 Field inspection and approval of growing crops at critical stages for verification of
genetic purity, detection of mixtures, weeds, and for freedom from noxious
weeds and seed-borne diseases etc.
 Sampling and sealing of cleaned lots.
 Growing of samples of potentially approved stocks for comparison with authentic
stocks.

5.  Various steps suggested by Hartmann and Kester (1968) for maintaining genetic purity
 Providing adequate isolation
 Roguing
 Periodic testing of varieties for genetic purity.
 Avoiding genetic shifts by growing crops in areas of their adaptation only.
 Certification of seed crops to maintain genetic purity and quality of seed.
 Adopting the generation system.
 Grow out tests
2.2. The important safeguards for maintaining genetic purity during seed production are
1. Control of seed source
 Use of seed of an appropriate class of seed and from an approved source
2. Preceding crop requirements
 To avoid contamination through volunteer plants and also soil borne diseases.
3. Isolation
 Due to natural crossing with other varieties grown alongside and off-types present in
the seed field; contamination due to mechanical mixtures at the time of sowing,
harvesting, threshing, processing and handling of seeds and contamination due
to seed-borne diseases from nearby fields.
4. Roguing of seed fields
 Existence of off-type plants, i.e., plants differing in their characteristics from those of
seed variety is another potent source of genetic contamination.
 Three main sources of off-types:
 May arise due to presence of some recessive genes in heterozygous
conditions at the time of release of varieties.
 Volunteer plants arising from accidentally planted seed or from seed produced
by earlier crops.
 Mechanical mixtures
5. Seed certification
 Genetic purity in commercial seed production is often maintained through a system of
seed certification.

6.  Principal objective of seed certification is to maintain and make available crop seeds,
tubers, or bulbs and some-times turf grasses.
 To accomplish these purposes
 Qualified and well experienced personnel of seed certification agency carry out
field inspections at appropriate stages of crop growth.
 Also make seed inspections to verify that the seed crop/seed lot is of the requisite
genetic purity and quality, after harvesting to verify quality, and at the processing
plants, draw samples for seed testing and sometimes for grow-out tests also.
 In addition to inspections, seed certification agency also lay down the field and
seed standards to which the seed crop and seed lot respectively.
 Field standards - land requirements, isolation requirements, maximum permissible
off-type, shedding tassels (in case of hybrid maize production).
 Seed certification implies that both the seed crop and seed lot have been duly
inspected.
6. Grow-out tests
 Periodically tested for genetic purity by grow-out tests