1) Pollinators play an essential role in seed production of many crops as they transfer pollen between flowers, enabling cross-pollination and sexual reproduction. 2) Effective pollinators for seed production must efficiently remove and deposit pollen, exhibit flower constancy by primarily visiting flowers of the same species, and have foraging behaviors suited to the flower traits and needs of the crop. 3) Understanding the floral biology, pollinator species present, and foraging behaviors can help identify the most efficient pollinators to utilize for seed production of different vegetable, spice, pulse and oilseed crops.

1. POLLINATORS
FOR VEGETABLE SEED PRODUCTION
V.V. Belavadi
Emeritus Scientist (Entomology)
University of Agricultural Sciences, Bangalore
Seed Tech Trg Prg: 29/10/18

2. Importance of pollinators
NumberofCrops
(Klein, 2007)

3. • Biological species concept
–Species is a group of actually or
potentially interbreeding population
which is reproductively isolated from
other such groups
–How does a new species form?
potentially interbreeding population
reproductively isolated

4. “.. I was much struck how entirely vague
and arbitrary is the distinction between
species and varieties”
Charles Darwin, 1859
• Species is dynamic!!

5. Darwinian Tenets
• Individuals within a population of a
species are variable
• Some of these variations are passed on
to the offspring
• In every generation more offspring are
produced than can survive to reproduce
• Survival & reproduction are not random
The individuals that survive and go on to reproduce
are those with the most favourable variations.

6. Conventional breeding
• A population with high variability
• Identify certain members of the
population with traits that are useful
• Initiate sexual recombination that
allows segregation and combination of
traits in the offspring
• Identification of individuals that
exhibit the most ‘useful’ inherited traits
• Selection and multiplication not random
H
um
an
m
anipulated
Evolution?

7. • Most, if not all, of the
hybridization work carried out
has used genetic variability
within species

8. • Why plants need insects for pollination?
– How this relationship evolved and is
sustained?

9. • Sex has always been difficult for
plants, because they cannot move.
• If one cannot move, then finding a
suitable partner for reproduction
becomes almost impossible!
• 135 mya, plants discovered wind
pollination.

11. • Wind pollinated plants produce a large
number of pollen - success rate is low
and great majority of pollen goes waste
• Nature seldom tolerates waste, and it
was only a matter of time before the
plants arrived at a better solution in the
form of insects.

12. • Pollen is nutritious.
• Some winged insects soon began feeding
on it and before long some became
specialists in eating pollen.
• Flying from plant to plant in search of
their food, these insects accidentally
carried pollen grains upon their bodies,
trapped amongst hairs or in the joints
between their segments.

13. • When the occasional pollen grain fell off
the insect on to the female parts of a
flower, that flower was pollinated.
• And so insects became the first
pollinators or sex facilitators for plants.
• Although much of the pollen was consumed
by the insects, this was still a vast
improvement over their dependence on
wind.

14. • But still there was a problem – the early pollinators
had difficulty in spotting the flowers, since the
flowers were no different from the surrounding
vegetation!
• In order to attract insects, they had to get better &
“advertise” their flowers with a different colour than
the surrounding vegetation!
• Thus began the longest marketing campaign in
history, with the early lilies and magnolias the first
plants to evolve petals, conspicuously white against
the forests of green.

15. • With this new reliable means of pollination,
insect-pollinated plants became enormously
successful and diversified.
• Competition for pollinators resulted in
evolving bright colors, patterns and elaborate
shapes.
• In this battle to attract pollinators, some
flowers evolved an additional trick — they
began producing sugar-rich nectar as an extra
reward – possibly to save pollen!

16. • As these plants proliferated, the
opportunities for insects to specialize
grew; butterflies & some flies evolved long,
tubular mouthparts to suck up nectar.
• The most specialized and successful group
to emerge were the bees, the masters of
gathering nectar and pollen to this day.
• The first true bees appeared around 130

18. • Today, the majority of flowering plants
use insects, mostly bees, to carry their
pollen.
• Bees have one clear advantage over wind:
they can track down another flower of
the same species, so a plant species need
not produce huge amounts of pollen.
• This was the basis for the theory about
the rise of angiosperms: pollination was
more efficient.

19. Myth : Plants bear flowers which become fruits
We take pollination for granted

20. How many flowering plants ?
• There are an estimated 352,000 species
of flowering plants in the world (Paton,
2008)
• Of these, 87.5% (3,06,000) species
entirely or partially depend on flower
visitors for successful seed set
(Ollerton et al., 2011)

21. • 87 of the 115 global food crops
depend upon insects for pollination,
– 35 percent of global food production.
–Klein, 2007
• Annual economic value of pollination
service worldwide is about € 153
billion
–Gallai et al., 2009

22. Change in relative yield over years for pollinator dependent,
crops with high Pollinator dependence and
pollinator non-dependent crops
Basu et al., 2011

23. Pollination: Why is it important?
• Pollinators are Vectors for genetic exchange
– Largely responsible for the genetic variation
• Pollination is an essential service to crops
and wild plants
• Essential in obligate mutualisms
• Provide other ecosystem services
• Biodiversity value

24. Pollinators for seed production

25. Myth 1 : Plants bear flowers which become fruits
We take pollination for granted

26. Do we value Pollinators ?
• Excessive use of chemicals
• Monoculture
• Deforestation
– Habitat destruction
– Loss of flora that sustain pollinator
populations
 have lead to decline in pollinator
populations in cultivated systems
as well

27. Life on Earth
• Earth originated 4,500 my ago
• Life – 3,750 my ago
• Insects – 400 my ago
• First flowering plants 125 my ago
• First flower visiting insects 125 my ago
• Bees- 100 my ago
• Radiation among Angiosperms 65 my ago
• First Hominid – 4.00 my ago
• Homo habilis– 2.18 my ago
• Homo sapiens – 0.16 my ago
POLLIN
ATOR
M
EDIATED
EVOLUTION

28. Why are pollinators important?
Pollinators are vectors of genetic
exchange
They are important in Sexual reproduction of
plants
Increase variability in offspring, creating
diversity and variation among populations (gene
shuffling)
Variation needed for Natural Selection to
occur leading to evolution of new
varieties/species
Out-breeding is good! (inbreeding is bad…)

29. • Insects can be used in crop
improvement programmes and in
seed production
–Vegetable crops
–Some spice crops
–Some pulse crops
–Oilseed crops

30. • Seed Production – Seed Multiplication
– Quality
– Quantity
• Crop Improvement
– Development of Hybrids

31. Utilizing pollinators for seed
production
Myth 3 : When we think of bees
we think of only honey bees!!
Myth 2 : When we think of pollinators
we think of only bees!!

32. There are only ten species of
honey bees
20,000 species in the world
(estimates: 25000);
750 species in India
How many bees?

33. Bees for Seed Production
• The Crop
– Plant characters
– Flower characters
– Pollination syndrome
• Pollinator
– Efficiency
– Dependency

34. Prerequisites
• Floral biology of the crop
– When does it flower? Season, months
– What is the flowering duration?
– When is the anthesis? & Pollen dehiscence?
– Nature of pollen – sticky, powdery
– # of pollen grains/flower
– Pollen viability,
– stigma receptivity
– # of ovules/flower
– Longevity of flower
– Flower structure
Pollen – Ovule ratio

35. • Insect visitors:
–Species
• Identify the Potential pollinator
• Pollen removal efficiency index
PREi = Ri – N / V – N
 Ri mean # of pollen grains removed per
flower with a single visit by species i;
 N mean # of pollen grains removed per
flower that received no visits
 V mean #of pollen grains removed per
flower receiving unrestricted visitation by
bees.

36. • Pollination Efficiency Index
PEi = Pi – Z / U – Z
–Pi mean # of seeds set in flowers that
received only one visit by species i;
–Z mean # of seeds set in flowers that
received no visits and
–U mean # of seeds set in flowers that
received unrestricted visits.

37. Foraging behaviour of
pollinator
• Time of activity*
• Rewards collected
• Time spent per flower
• # of flowers per visit*
• # of visits to a single flower*
• Movement pattern*
• # of trips/day
• Patch fidelity *

38. Foraging activity of A.cerana bees in
different times of a day
0
5
10
15
20
25
30
35
40
#ofbees/clump
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
Time of day

39. Number of flowers visited by a
forager on successive trips
0
20
40
60
80
100
120
140
Numberofflowersvisitedper
trip
I II III IV V VI VII
Trip Number

40. Relation between number of bee visits per flower with the
number of pollen grains deposited on the stigma
y = 1.3603x + 3.9307
R2
= 0.8458
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60
Number of visits
#ofpollengrainsonstigma

41. 0
50
100
150
200
250Numberofvisits
15 30 45 60 75 >75
Distance from previous flower

43. Patch fidelity in foraging honey bees
at cardamom clumps.
0
10
20
30
40
50
60
70
Percentvisitstoclumps
Base
Clump
1.8 3.6 5.4 7.2 9
Distance from the base clump (m)
A. cerana
A. dorsata

45. Myth 3 : Bees mix up varieties !!
Very rare

46. • Flower constancy
• Patch fidelity
• Advantage for seed production
• Disadvantage for hybridization?
Pollinators are faithful to the flowers of one
plant species to minimize the costs of relearning
flower-handling skills after every switch.

47. • Bees have memory constraints
• They have to remember their way back to
hive
• They cann’t be flying to different parts
of a field or different fields
• If they have to visit two different types
of plants, they have to learn to handle
the flowers of both species & remember!
• Hence a very wide isolation distance for
seed production blocks may not be
necessary

48. ………insects should visit flowers of the same
species far as long as they can - is of great
significance to the plant, as it favours cross
fertilization of distinct individuals of the same
species; but no one will suppose that insects act
in this manner for the good of the plant. The
cause probably lies in the insects being thus
enabled to work quicker; they have just learnt
how to stand in the best position, and how far
and in what direction to insert their proboscides.
Darwin (1876)“Darwin’s interference hypothesis”

49. • Hence, this can be a great
advantage for using bees in
seed production!

50. Pollinator mediated seed
production
• For crossing to occur between two lines,
– flowering phenology should be similar
– flower structure – colour, shape and size
should be similar
– Bees should not descriminate between the
two lines but switch between lines in a
single foraging bout
- Wolf et al. 2001

51. • When you have two lines, a pollen
donor and female parent
–It is important to observe the
foraging behaviour of bees
–Movement pattern:
• How often they visit female line?
• After how many visits to male line?
–Planting architecture

52. Seed production in Bitter gourd
Male flowerMale flower
Female flowerFemale flower
Monoecious

53. Anthers &
pollens
Corolla
Structure of staminate flowers
Pollen grains
Nectar
gland
calyx
Male bud

54. Stigma
Ovary
Structure of pistillate flowers
Bud
ovary
Stigma
Ovules
calyx

56. Comparison between time of pollen viability, stigma receptivity
and activity of pollinators

57. Comparison of fruit weight and seed number with different
pollination treatments (n=25 fruits)
Treatments
Fruit weight (g) Number of seeds
Open pollination (A) 145.68 27.28
Hand pollination (B) 165.72 32.00
Green house + A. cerana
pollinated (C)
207.92 38.32
Open pollination +
A. cerana (D)
155.68 30.40
T test
A*B -1.40 NS -3.47 NS
A*C 7.64* 13.89*
A*D -0.82 NS -2.21 NS
B*C 3.07* 4.51*
B*D 0.58 NS 1.02 NS
C*D 4.65 * 5.29 *
T-Critical Value: 2.06; *Significant at 5% level; NS- Non significant

58. Fruit set and seed number with
different pollination treatments in bitter gourd

59. Comparison of fruit set and seed number in 1:1, 1:2 and
1:4 (Male: Female) ratio in bitter gourd across seasonal
variation during Kharif-2016 and Summer-2015 season
Treatments
Kharif-2016 Summer-2015
Fruit wt
(g)
No. of
seeds
Fruit wt
(g)
No. of
seeds
1:1 Ratio (A) 249.12±45.30 35.88±3.85 231.78±35.38 32.96±7.10
1:2 Ratio (B) 269.38±41.63 37.50±4.52 243.72±43.86 33.94±5.53
1:4 Ratio (C) 91.52±12.03 7.52±2.06 85.94±8.37 6.62±1.78
Hand pollination(D) 241.56±28.93 32.98±6.69 207.98±38.77 24.72±5.40
Z Test
A*B -2.32 NS -1.92 NS -1.49 NS -0.76 NS
A*C 23.77** 45.84** 28.35** 25.43**
A*D 0.99 2.65* 3.20* 6.52*
B*C 29.01** 42.61** 24.98** 33.24**
B*D 3.87* 3.95* 4.31* 8.43*
C*D 33.85** 25.68** 21.75** 22.49**
z - critical value 1.96, * -Significant at 0.05 level, ** -Significant at 0.01 level and NS- Non significant

60. Fruit set and seed number in 1:1, 1:2 and 1:4 (Male:
Female) ratio in bitter gourd
Tharini & Belavadi, 2016

61. Per cent seed germination in natural pollination, hand pollination, A. cerana + green
house, 1:1, 1:2 and 1:4 ratio in bitter gourd

62. Valuation of pollination service to bitter gourd
Treatments
Fruit
weight(g)
(n = 30)
Seed
number
(n = 30)
Seed
weight (g)
(n = 30)
Fruit yield
t/ac
Seed
yield
q/ac
Gross
income
(Rs.)
Cost of
cultivation
(Rs.)
Net
income
(Rs.)
B: C
Ratio
Open pollination 145.68 27.28 0.35 5.83 3.81
4,58,280.0
0
54,500.00
4,03,780.
00
1: 7.40
Hand pollination 165.72 32.00 0.41 6.63 5.24
6,28,800.0
0
68,000.00
5,60,800.
00
1: 8.25
Green house + A.
cerana
207.92 38.32 0.42 8.32 6.43
7,72,560.0
0
1,69,167.
00
6,03,393.
00
1: 3.57
Open pollination +
A. cerana
155.68 30.40 0.41 6.23 5.04
6,05,520.0
0
62,500.00
5,46,020.
00
1: 8.73

63. • Though the ovule number per female flower
was nearly 60 in bitter gourd but only a
maximum seed set 38 and 27 was achieved.
• Deficit in pollinator population and hence
there is a need for introduction of bee
colonies for higher seed set for seed
production.
• Conserve and manage the native pollinator
populations so that farmers can get good
quality and quantity of bitter gourd fruits
with more viable seeds.
• Bees can be effectively used for seed
production.

64. Thank you