2. INTRODUCTION
Onion (Allium cepa L.) is a major bulbous crop
among the cultivated vegetable crops and it
is of global importance.
Top 3rd vegetable with production of 1.064 mT
15.118mha.
India needs around 7000 tonns of seeds
annually.
3. Anthesis occurs in early morning (6-7 hrs).
Anther dehiscence is between 7.00 and 17.00 hr and on next
day also with peak between 9.30 and 17.00 hr.
Pollen fertility is highest on the days of anthesis.
Stigma receptivity is also high on the day of anthesis (Jones,
1933).
The duration of anthesis is approximately 4 weeks on
individual umbel.
.
FLORAL BIOLOGY
4. FLORAL BIOLOGY
The anthesis begins from outer flowers and goes centrally
in succession
The flower is protandrous in nature and stigma becomes
receptive when shedding of pollen is over.
5. Onion is cross- pollinated in nature and bees, flies and other
insects do pollination.
It is essential to ensure that there is sufficient population of
pollinating insects to achieve the full potential of onion
seed.
It is also possible in some situation to encourage the
development of increased blowfly population by
distributing suitable carrier or dried fish among the
flowering crop (Currah and Proctor, 1990).
POLLINATION
6. LAND REQUIREMENT
Land to be used for seed production of onion should be free
from volunteer plants.
Although onion can be grown nearly in all types of soil
from sandy loam to loam. heavy clay soil should be
avoided, but unless they are satisfactory well supplied
with humus to lighten them.
The soils pH should preferably be 6.0-6.8.
7. CLIMATE & SEASON
It is being a short day favored crop it is advised to grow
during rabi season for seed production.
Desai et al reported that temperature around 21.1°c
favours vegetative growth, where as lower temperature
around 12.8°c are continue to seed stalk formation and
shortday condition also favours to seed production.
8. METHODS OF SEED PRODUCTION
There are two methods of seed production.
Seed to seed method
Bulbs to seed method
Both the methods are in use in onion seed production.
But bulb to seed method is most commonly used method of
seed production.
9. SEED TO SEED METHOD
In this method seedlings are transplanted in first week of
October and allow over-wintering at the same place and
allowing bolting (flowering).
The seed are threshed from the mature umbel.
This method does not allow to examine the mature bulb
characters and field is rogued for off-types.
Seed to seed method is not popular, since all the variety are
not suitable for annual seed production due to poor
bolting habit and lower seed yield.
10. SEED TO SEED METHOD CONTINUED…
The seed produced in this method is not suitable for further
multiplication.
The seeds produced from this method having low genetic
purity,
But advantage here is low cost of seed production
compared to bulb to seed method.
11. BULB TO SEED METHOD
Here in first season bulbs are produced, which after maturity
are harvested and bulbs which are true to type are sorted
and stored.
The rabi and late kharif varities are stored for next season and
kharif varities are given rest for 15-30 days.
The stored bulbs are planted in the next season to produce
seeds.
Top 1/3 portion of the bulb is cut to examine the number of
axis of growing center preferably single centered and
medium to large sized bulbs should be chosen and soaked
in Ig/litre bavistin & corbosulphon 1m/litre.
12. This method is widely practised it allows us to examine the bulb
characteristics and rouging of undesirable bulbs hence genetic
purity is high in this method of seed production
One hectare of bulbs from the first year will plant 3-5 ha for the seed
production.
The bulbs selected for seed production and usually referred to as
mothers bulbs. 4-6 cm size bulbs are selected for getting good
crop (Pandey 1996).
BULB TO SEED METHOD CONTINUE…
13. FERTILIZERS
FYM @ 25 tons/ha,
NPK @ 100:50:50 kg/ha apply 50:50:50 kg/ha NPK at the time of
planting & remaining nitrogen in 2 splits, one at 30 days and 2nd
at 45-60 days after planting.
Give 1% spray of Poly feed (19:19:19, NPK) at 30 & 60 days after
planting & one spray of multi K (0:0:50) after 60 days of planting.
14. ISOLATION
For mother bulb production 5 m isolation should be maintained.
Since onion is cross pollinated through insect (entomophilous) two
varieties have to be well isolated from each other.
An isolation distance of 1000 m for foundation seed and 500 m for
certified seed shall be provided all round a seedfield to separate
it from fields of other varieties, fields of the same variety not
confirming to varietal purity requirement for certification.
15. SOWING SEASON
The seeds are sown in may-June for harvesting of bulbs in October-
November.
Selected bulbs are planted in November-December to produce seed in
April-may for use in the next season.
Oct.-Nov. planting is the best time for tropical types.
Dharm Singh and Ranjeet Singh (1991)stated that the best time for
bulb planting is 3rd week of October.
Malik et al. (1999) reported that highest yield and quality of seed was
recorded for 15th October planting.
Bulbs must be stored in well-ventilated storage structure with
temperature 25-30°C and RH 65- 71%.
16. SEED RATE & SOWING
Spacing: 15 x 10 cm bulb production.
45 x 30 cm, 60 x 20 cm (on drip)
Bulb Rate
Total of 25-30 quintal bulbs are needed for one ha. depending on
the size of the bulb (Pandey, et al.)
Weed Management:
Spray Goal @ 1.5 mI/L after planting of bulbs and one weeding after
45 to 60 day after planting should be done.
Weedicides like pendimethalin at 2.5-3.5 litlha or oxyflorofen at
0.15-0.25 liters ha with one hand weeding at 45 days given good
control of weeds.
17. IRRIGATION AND AFTERCARE
• Irrigation is given at 7-10 days interval depending on
types of soil and season.
• Earthing is done 2 months after transplanting to avoid
lodging. Weeding and hoeing are done as per
requirement.
18. FIELD INSPECTION
A. Mother bulb production stage
• First inspection shall be made after transplanting of
seedlings in order to determine isolation, volunteer
plants, off-types including bolters and other relevant
factors.
• The second inspection shall be made after the bulbs
have been lifted to verify the true characteristics of
bulbs.
19. FIELD INSPECTION
B. Seed production stage
• The first inspection should be made before flowering in
order to determine isolation, off types including
bolters and relevant factors.
• The second and third inspection shall be made during
flowering to check isolation, off types and other
relevant factors.
• The forth inspection shall be made at maturity to verify
the true nature of the plant and other relevant factors.
20. ROGUEING
Plot should be visited regularly.
Yellow and lanky plants should be removed before
flowering.
Plants with differential umbel height should be removed
before opening of flowers.
Plants affected by aster yellow and stemphyllium blight
should be removed before seed harvest.
21. MEASURE TO IMPROVE POLLINATION
Following points should be taken care of for improving the
pollination.
• Bee colonies should be kept in field .
• Irrigation should be given more frequently at the time of
flowering and seed setting.
• Only safer insecticides should be sprayed during flowering.
• In case of high wind, sometimes bees do not sit on the
flowers. To avoid this plant wind breakers all round the
field.
22. MATURITY, HARVESTING AND CURING
All seed heads do not mature simultaneously, therefore, harvesting is done
in installments.
When seed inside capsules become black and 20-25% black seeds are
exposed the umbels should be
cut with 10-15 cm stem attached. The umbels are spread on ground or
canvas to avoid attack of mould for drying.
When seed inside capsules become black and 20 - 25% black seeds are
exposed, the umbels are cut with 10 – 15 cm of stems attached.
• The optimum moisture content is 10 to 15 per cent at the time of
harvesting (Khurana and Mehra, 1986; Brewster 1994)·.
• The heads are spread on ground or canvas to avoid attack of mould and
obtain uniform drying.
24. POST HARVEST MANAGEMENT
Cleaning
• Onion seed can be cleaned using any regular screening and fanning
mill, after which it is separated by employing gravity separators.
• For safe storage, seeds are dried to a level of about 6% moisture and
then packed in aluminium foils or tins.
• Then it is stored in air conditioned and dehumidified store having a
temperature of 20-25ºC and relative humidity of 30-40%.
• In hot and humid climate, viability of onion seed is lost within an year.
• Onion seed if dried to 6.0% moisture level and stored in sealed
containers, its life may be prolonged to 3-4 years without evident
loss in seed germination.
25. Seed yield:
500 - 800 kg seed/ha, in best management and climatic
conditions 1000
to 1200 kg seed can be obtained.
Grading
Seeds are size graded using BSS10 X10 wire mesh sieve
and the seeds retained by
this sieve alone is recommended for sowing/storage.
26. CERTIFICATION STANDARDS-FIELD STANDARDS
Contaminant Isolation distance (m)
Mother bulbs production Seed production
Foundation
Seed
Certified
Seed
Foundation
Seed
Certified
Seed
(A) General requirements
Field of other variety 5 5 1000 500
Field of the same
variety notconforming
to varietal purity
requirement for
certification
5 5 1000 500
(B) Specific requirements
Bulbs not confirming
to the varietal
characteristics
0.10% (by
number)
0.20% ( by
number
**Off-types 0.10% 0.20%
29. HYBRID SEED PRODUCTION
I.Hand emasculation and pollination :
Flowers are very small, androgynous, very few seeds/ cross. It is
time and labour combursum, so, it is not economical. Not
followed also.
II. Use of Male sterile lines-4F:1M
a) CMS :commonly used
b) CGMS : also used but high cost of production.
30. USE OF MALE STERILE LINES
In onion the use of male-sterile lines is common to
produce seeds of F1 hybrids.
The male sterility in onion is due to the interaction of
cytoplasm and nuclear gene
The nuclear gene is single recessive msms while its
dominant allele MsMs is for male fertility.
31. PARENTAL LINES
Three parental lines, namely A, B and C, are used for hybrid
seed production.
The line A, known as the female parent, is male sterile having
the genetic constitution Smsms, which produces hybrid
seeds,
The line B with the geno-type Nmsms is the male-fertile
counterpart for the maintenance of male sterility of line A
The line C is the fertile pollen parent or inbred which is
genetically diverse from the lines A and B.
32. PROCEDURE
The hybrid seed is produced in the open in an isolated field.
The bulbs of A (male sterile) and C (pollen parent) lines are planted
alternately in a ratio of 4 rows of the A line to 1 row of the C line.
Sometimes 8 rows of the A line are alternated with 2 rows of the C line.
The flowering in the lines A and C must synchronize. If it does not, it can be
accomplished by adjusting planting dates of the lines A and C.
Daily rogueing of pollen-bearing plants and other off-types in the line A in
the morning before the anthers dehisce is essential.
When the seed of the line C is not to be saved its flower stalks may be cut
and destroyed as soon as the pollination is completed.
