Introduction
Pollination is one of the most important mechanisms in the maintenance and promotion of biodiversity and, in general, life on Earth. Many ecosystems, including many agro-ecosystems, depend on pollinator diversity to maintain overall biological diversity. Pollinators strongly influence ecological relationships, ecosystem conservation and stability, genetic variation in the plant community, floral diversity, specialization and evolution. Pollination also benefits society by increasing food security and improving livelihoods. Pollinators are extremely diverse, with more than 20,000 pollinating bee species and numerous other insect and vertebrate pollinators.
Pollination: The transfer of pollen from the anthers of a flower to the stigma of the same flower or of another flower. SELF POLLINATED CROPS
Self-pollinated crop species occupying less than 15%
CROSS POLLINATED CROPS
The remaining cross-pollinated crops need help of pollinating agents, wind, water or insects for fertilization.
ď ś Several essential inputs such as improved seeds, improved implements ,irrigation ,fertilizers and pesticides are being used for improving the productivity but these components even when fully exploited may not give marginal returns if the desired level of pollination is not achieved.
ďƒźPollination and fertilization are the important events in seed development and maturation (Ragini and Vanangamudi,2006). ďƒź Deployment of insect pollinators is considered as one of the cheapest and eco-friendly approaches in maximizing the yield of cross pollinated crops (Free, 1970). Though butterflies ,moths, beetles ,thrips ,birds play a role in pollination ,Honey bees are the ideal pollinators.
Pollinators:
ď ś An animal that moves pollen from the anthers
to the stigmas of flowers, thus effecting pollination. Animals that are known to be good pollinators of flowers include bees, butterflies, hummingbirds, moths, some flies, some wasps, and nectar feeding bats.
Beetle Pollination The least specialized flowers are members of subclass Magnoliidae. These are often pollinated by beetles, although beetles also visit a wide variety of flat flowers (or flat inflorescences that function as single flowers). Some general features of beetle flowers are: Time: Either day or night Structure: Actinomorphic, numerous floral parts; large bowl shaped, ovules protected Color: Dull, white, few visual attractions, no nectar guides Scent: Strong, fruity or aminoid; no nectar, food primarily pollen or food bodies Carrion & Dung Beetles & Flies Time: Either day or night Structure: Actinomorphic, deep corolla tube with appendages forming traps Color: Purple, brown (like meat), no nectar guides or nectar Scent: Strong, like rotting meat .
Value of pollinators Animals pollinate approximately 75 percent of the crop plants grown worldwide for food, fiber, beverages, condiments, spices, and medicines. It has been calculated that one out of every three to four mouthfuls of food we eat and beverages we drink is delivered to us by pollinators. As such, agricultural products that are produced with the help of pollinators make a significant contribution to the economy. For example, it has been estimated that insect-pollinated crops directly contributed $20 billion to the United States economy in the year 2000. They also perform key roles in natural ecosystem. By helping to keep plant communities healthy and able to reproduce naturally, native pollinators assist plants in providing food and cover for wildlife, preventing erosion, and keeping waterways clean. Pollinated plants produce fruit and seeds which are a major part of the diet of approximately 25 percent NRCS of bird species, as well as many mammals. Excessive use and improper application of many pesticides impact pollinators and their habitats. Some insecticides directly kill pollinators, particularly pollinating insects, and herbicides reduce forage plant diversity by killing wildflowers.
Crops dependent upon or benefited by insect pollination Legumes
Beans, Cowpea, Lima Beans, Lupines, Mung Bean/Green or Golden Gram, Soybean
Vegetables
Asparagus, Beet, Broccoli, Brussels Sprouts, Carrot, Cauliflower, Celery, Cucumber, Eggplant, Endive, Green Pepper, Leek, Lettuce, Okra, Onion, Parsnip, Pumpkin, Radish, Rutabaga, Squash, Tomato, Turnip, White Gourd
Fruits, berries and nuts
Almonds, Apple, Apricot, Avocado, Blackberry, Blueberry, Cacao, Cashew, Cherry, Chestnut, and nuts ,Citrus, Coffee, Coconut, Date, Fig, Gooseberry, Grapes, Guava, Huckleberry, Kiwi, Kolanut, Litchi, Macadamia, Mango, Olive, Papaw, Papaya,Passionfruit, Peach, Pear, Persimmon, Plum, Pomegranate, Raspberry, Strawberry, Tung, Vanilla, Watermelon
Oils, seeds and grains
Alfalfa, Buckwheat, Canola, Flax, Oil Palm, Safflower, Sesame, Sunflower
Clover and relatives
Arrow leaf Clover, Ball Clover, Berseem Clover, Black Medic/Yellow Trefoil, Cider Milkvetch, Crimson Clover, Lespedeza, Peanut, Persian Clover, Red Clover, Rose Clover, Strawberry Clover, Subterranean Clover, Sweet Clover, Trefoil, Vetch, White Clover
Other crops
Cotton, Kenaf & Cosmos, shoe flower, Golden rod, Cup & saucer, Tacoma stans, zinnia, coral creeper (Antigonon leptopus), rose, rangoon creeper, aster, wild rose (kuja), hydrangea, violet, portulaca, poinsettia, honey suckle, corn flower, coreopsis, dandelion etc.
&ornamental
Honey bee pollinating crops APPLE
COFFEE
SUNFLOWER
PUMPKIN
CITRUS
CHILLI
Almond garden
Clover crop
Blueberries
SQUASH
TOMATO
RADISH
Cosmos
Aster
Edward rose
Hibiscus
Tecoma stans
Golden rod
Zinnia
Coral creeper Rangoon creeper
Pollinated crops Water melon
Radish Carrot
Ridge gourd
Pumpkin
cotton
Rapeseed flower
Cucumber
Lucerne
Pigeon pea Sunflower
Niger 17
pollinated by Bats
moth
BEE FLORA AND POLLINATION OF CROPS
Bee visits plants for its fidelity of bees is due to sugar contents and pollens getting food for the bees number of crops.
food, nectar and pollen. This floral their preference for nectars having with higher nutritive values. Besides as a result of their visit pollinate a
Qualities of honeybees which make them good pollinators Body covered with hairs and has structural adaptation for carrying nectar and pollen. Bees do not injure the plants Adult and larva feed on nectar and pollen which is available in plenty Considered as superior pollinators, since store pollen and nectar for future use No diapauses is observed and needs pollen throughout the year Body size and proboscis length is very much suitable for many crops Pollinate wide variety of crops Forage in extreme weather conditions also
Yield increase due to bee pollination
Crop
Per cent yield increase
Mustard Sunflower Cotton Lucerne Onion Apple
43 32-48 17-19 112 93 44
Scope of beekeeping for pollination in India: Total area of bee dependant crops in India is around 50 million hectare. One hundred and fifty million colonies are needed to meet this, at the rate of 3 colonies per hectare. In India at present, there are only 1.2 million colonies exist. Hence there is a wide scope for expansion of bee keeping for pollination in India.
Management of bees for pollination
Place hives very near the field source to save bee's energy. Migrate colonies near field at 10 per cent flowering. Place colonies at 3/ha for Italian bee and 5/ha for Indian honey bee. The colonies should have 5 to 6 frame strength of bees, with sealed brood and young mated queen. Allow sufficient space for pollen and honey storage
ďƒ˜Usually a honeybee can visit between 50-1000 flowers in one trip, which takes between 30 minutes to four hours. In Europe, a bee can make between seven and 14 trips a day. A colony with 25,000 forager bees, each making 10 trips a day, is able to pollinate 250 million flowers.
Pollination by bees - case studies with selected crops
Sunflower
Alfalfa or Lucerne
1. Sunflower: It is a cross-pollinated crop. The pollen of the plant cannot fertilize ovary of same plant. Pollen source should be from different plant. Hence, honey bees acts as important agents for pollination in sunflower. In sunflower, yield increases even up to 600 per cent due to bee pollination. It improves quality and quantity of seeds. Oil content also increases by 6.5 per cent in seeds. To achieve this it requires five strong C. indica colonies or three A. mellifera colonies. Mostly irrigated crop is preferred by bees.
2. Cucurbitaceous vegetables: Cucurbits are monoecious with staminate and pistil late flowers in same plant. Due to bee pollination fruit set increases up to 30 to 100 per cent. 3. Alfalfa or Lucerne: These plants have tubular flowers with 5 petals joined at base. They posses one large standard petal, 2 smaller petals on sides and 2 keel petals holding staminal column. When bee sits on a keel petal, stamina column strikes against standard petal resulting in shattering of pollen. This is called tripping. Seed set occurs only if bee sits to trips the flowers. 4. Coriander: In coriander yield increases up to 187 per cent due to pollination. 5. Cardamom: It is an important commercial crop depending on bees for pollination. Here yield increases up to 21 to 37 per cent. 6. Gingelly: Another oilseed crop where bee pollination causes 25 per cent increase in yield. 7. Apple: In apple seed set occurs only if it is pollinated by bees. Fruit is formed only around the seeds. If improper seed set occurs fruit shape is lopsided resulting in decreased market value.
ď śIt is now apparent that most of the pulses and oilseeds, fruits and orchard crops including vegetables heavily depend on bees for their pollination. ď śThis is also true for seed production of vegetables like onion, cabbage, cauliflower, tobacco, sun hemp, Alfa Alfa and clovers. The number of colonies of honeybees required per hectare very much depends on the strength of foraging bees in the colony, the crops and prevailing weather conditions. ď śThe optimum number of colonies of average strength may range from 3 to 9 colonies per hectare, since the bees usually forage within a radius of about 1 to 2 km to harvest their nectar and pollen loads, and then return to their own hive.
Important features of flower which aid in Honey bee pollination Colour of the flower Structure of the flower Good quality nectar High concentration of sugars in flowers Production of Abundant pollen
Honey bee species involved in pollination • • • • •
Apis mellifera( European bee) Apis cerana indica(Indian bee) Apis dorsata (Rock bee) Apis florea (Little bee) Trigona irridepennis (stingless bee) Stingless bees
European bee
Rock bee
Indian bee Little bee
Apis mellifera is generally preferred Adoptability Easy handling Slow swarming Tolerance to human management Honey making habit increases pollination
Factors which influences pollination efficiency • A biotic factors Rainfall Temperature:16OC - 41OC Wind velocity: Below 15 miles/hr (Ragini and Vanangamudi,2006)
• Honey bee spp. Body size with hairs Rock bee
Little bee
Pollen carrying ability
• Hives placement
• Stage of hive placement in the field
• Colony size: 8-10 combs of bees/hive, with more number of broods
•Other agronomic practices-Increases nectar production Timely application of fertilizers Irrigation (Especially during flowering)
Estimates of increased seed set due to pollinators have been made in different parts of the world
• • • • •
22-100% -Radish 100-300%-cabbage 100-125%-turnip 91-135%-carrot 345-500%-onion Gingras et al.,1999
Recommendation of bee hives in various important crops Crop Alfalfa
2.5-8
Crucifer
2.5
References Williams et al.,1995 Mayer (1986)
2.5-15
Scott-Dupree et al.,(1995)
2.5
Scott-Dupree et al .,(1995)
Carrot
5
Mayer and lunden (1983)
Cotton
2.5-5
Rapeseed Cucumis melo Attractiveness of the crop Number of wild bees Number of competing weeds
No. of hives per hectare
Cucumber
10
Levin (1986) Williams(1994)
Onion
10-25
Mayer et al., (1993)
Soybean
1-1.5
Sheppard et al.,(1995)
Gourds
2.5-5
Skinner(1987)
Sunflower
4
Williams (1994)
Water melon
5
Williams (1994)
Radish
5
Mayer and lunden (1983)
Strength and location of bee hives Weather Growers experience
Role of Pollinators It increases yield in terms of seed yield and fruit yield in many crops. It improves quality of fruits and seeds Bee pollination increases oil content of seeds in sunflower. Bee pollination is a must in some self incompatible crops for seed set.
Cross-pollination of Lucerne is vital to ensure that the maximum quantity and quality of seed is achieved. Cross-pollination is said to contribute about 89% of the seed yield. Wild pollinators visiting crops can increase the effectiveness of pollination, and thus the yields and quality of crop production. Profiles of practices that can affect the diversity and abundance of wild pollinators visiting crops give options for farmers and land managers to promote wild pollinators at different scales of management.
ďƒ˜Bee pollination not only results in a higher number of fruits, berries or seeds, it may also give a better quality of produce, and the efficient pollination of flowers may also serve to protect the crops against pests. ďƒ˜The better weight due to sufficient pollination arises from the development of all seeds in a fruit. ďƒ˜An apple, for example, will only develop all the seeds inside if it has been pollinated by several bees and fully fertilized.
Table 1. Role of insect pollination in seed production of Radish.
Parameter Fruit set (%)
Bee pollination
Self Per cent increase in bee pollination pollination over selfing
81.00
56.55
24.45
Siliqua length (cm)
13.213±2.140
6.832±0.911
91.93
No. of seeds/pod
8.163±1.923
4.816±1.201
78.84
Seed weight per 100 seeds (g)
1.500±0.316
0.9000±.260
66.67
Both the quantitative and qualitative characters were expressed better in case of insect pollinated flowers, due to frequent visits of the insect pollinators, Priti et al.., 2001
Table 2. Effect of honey bee pollination on seed yield & quality of Radish. Treatment Caged with Mean honey bees SD Open
Mean
pollination SD % increase in open over cage
Siliqua Siliqua/length
Grain
Yield/plant
/plant
(cm)
/siliqua
80.62
5.50
30.67
(g)
100-seed weight(g)
Germination (%)
2.02
1.25
0.87
76.80
0.24
0.25
0.54
0.08
17.94
84.92
5.48
4.30
3.67
1.06
91.00
24.11
0.31
0.64
1.47
0.10
5.81
-
-
112.87
193.63
21.83
-
Both the quantitative and qualitative characters were expressed better in case of open pollination due to frequent visits of the insect pollinators. Kapila et al.,2002
Table 3.Pollinating efficiency of Apis Species in hybrid seed production of Brassica napus L.
Treatments
Number of Seeds set per pod
A.mellifera
11.571
A.cerena
9.143
A.florea
6.857
CD (P=0.05)
1.896
Increased amount of pollen deposition on stigma by A.mellifera because of its large body size with more hairs Jasvir Singh et al., 2002
Table 4. Relative efficiency of various agents as pollination facilitators in Lucerne. Treatment
Pollination efficiency
Yield
Test weight
Germination
% increase over control
(q/ha)
87.41
119.56
5.55
3.27
91.33
30.37
-91.53
0.59
1.60
45.35
39.81
-
2.52
2.80
88
1.17
-97.06
0.15
1.58
40.66
Hand tripping
15.00
-62.32
1.60
2.48
-
walking
34.00
-14.59
2.46
-
-
Rope pulling
35.95
-9.96
2.42
-
-
(%) Plots caged with a bee colony Plots caged with out bees Open pollination Selfing
(g)
(%)
ďƒź Increase in the yield was due to combined effect of cross pollination and reduced ovule abortion ,because tripping mechanism carried efficiently by honey bees. ďƒź Decrease in the yield in other treatments may be due the absence of tripper and pollen carrier, damage to florets, stigmatic membrane might not have got ruptured. Padmavathi et al., 2003
Table 5. Honey bee pollination requirement for triploid watermelon. Honey bee visitation treatment No visits control 2 visits 4visits 8 visits 16 visits Open pollinated control (about 24 visits)
Fruit set%
Fruit no per plot
Fruit wt(kg)/ per plot
0* 9* 25* 38* 53* 80*
0.0* 1.8* 5.0* 7.5* 10.5* 16.0
0.0* 5.5* 32.0* 46.9* 68.8* 106.1
Maximum fruit set and development was recorded in open pollination compared to other treatments .Since triploid watermelon do not provide sufficient viable pollen to fertilize pistillate flowers, it requires more number of visits. Alan walters, 2005
Table 6. Effect of honey bee pollination on pumpkin (Cucurbita pepo) fruit yield.
Fruit/ha Pumpkin cultivar Appalachian Autumn king Gold rush Motherlode Aspern Gold strike Howden Ichabod Mean
Without bees 4,765 4,595 3,233 3,803 5,105 3,148 2,638 3,148 3,805
Bees 5,955 4,765 4,085 4,425 4,340 3,998 3,403 2,893 4,233
Total weight Without bees 26,242 27,260 23,712 22,930 27,198 20,136 14,888 16,454 22,353
Bees 44,755 35,363 33,846 33,781 30,134 28,754 24,394 21,347 31,547
Average fruit weight(kg) Without Bees bees 5.5 7.6 5.9 7.5 7.4 8.3 6.1 7.7 5.4 7.0 6.4 7.3 5.7 7.2 5.3 7.4 5.9 7.5
Alan Walters and Bradely, 2006
Table 7. Effect of honey bee pollination on pumpkin (Cucurbita pepo) seed yield. Pumpkin cultivar
Seeds/Pumpkin
Mother Lode
Without bees 551
Autumn king
Bees
Seed weight(g)/pumpkin Without bees
Seed weight/100 seed (g)
Bees
Without bees
Bees
700
78.4
106.4
14.8
15.7
644
684
86.8
100.8
13.7
15.1
Ichabod
555
633
64.4
103.6
10.9
16.8
Gold stike
531
609
75.6
86.8
14.3
14.3
Gold Rush
553
595
81.2
81.2
14.8
13.7
Appalachain
506
595
70.0
89.6
13.7
15.7
Aspen
503
590
78.4
109.2
15.4
18.8
Howden
591
570
78.4
86.8
13.4
15.7
Mean
554
622
75.6
95.2
13.7
15.7
It is due to increased pollen deposition on the stigma and high pollinator density with maximum pollination activity
Conclusion
ďƒ˜ On a global level, the Convention on Biological Diversity has identified the importance of pollinators . It is apparent that speculative and practical utilization of heterosis in terms of seed yield and quality are directly related to the role of insects principally bees in cross pollinated crops which exhibits male sterility and self incompatibility mechanism . Thus an effective pollination through careful planning and skillful management strategies in entomophilous cross pollinated crops can be achieved if strong bee hives are maintained in the apiaries beside tumbling pesticide application which are detrimental to honey bees. ďƒ˜ pollinators are increasing in seed yield also increasing total food production in the country.
Honeybees are the “ Angles of agriculture “, the farmers best friend . Using honey bees for crop production, the production can be increased manifolds , however it needs to be encouraged among farmers.
REFERENCES Bees and their role in forest livelihoods research paper . Encyclopedia Google scholar Vegetable seed production text book