ALLELOPATHY –A TOOL FOR WEED MANAGEMENT

Credit Seminar

SEMINAR INCHARGE & GUIDE

DR. M. L. KEWAT PROFESSOR

Department of Agronomy, JNKVV ,Jabalpur(M.P.)Department of Agronomy, JNKVV ,Jabalpur(M.P.)COLLEGE OF AGRICULTURECOLLEGE OF AGRICULTURE

JAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYAJAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYAJABALPUR(M.P.)JABALPUR(M.P.)

PRESENTED BY

POONAM CHOURASIYAEnrl. no. 160111009

ConceptConceptConceptConcept• The phenomenon of one plant having detrimental effect on

another through the production and exertion of toxic chemical compounds is called allelopathy. Allelopathy is the indirect harmful effect through exertion of chemical substances.

• Allelopathy is existent in the natural ecosystem and it occurs widely in the natural plant communities. Allelopathy is possibly a significant factor in maintaining the present balance among the various plant communities. Allelopathic substance was first detected by Davis (1928) in black walnut tree (Juglans nigra) whose foliar leachate containing Juglone was found to damage germination and seedling growth of crops beneath the tree.

ALLELOPATHIC PROBLEMS IN AGRICULTURE, HORTICULTURE AND FORESTRY

1)1)Soil sicknessSoil sickness

2)2)Auto toxicity under same crop monocropping.Auto toxicity under same crop monocropping.

3)3)Increased crop- weed interferenceIncreased crop- weed interference

4)4)Growing susceptibility of plants to disease/ pestsGrowing susceptibility of plants to disease/ pests

5)5)Reduced nitrification and biological nitrogen fixationReduced nitrification and biological nitrogen fixation

6)6)Reduced nutrient uptakeReduced nutrient uptake

7)7)Weed seed decomposition delayed/ preventedWeed seed decomposition delayed/ prevented

8)8)Poor success on replanting of tree cropsPoor success on replanting of tree crops

9)9)Failure of vegetative propagation (e.g. grafting, budding)Failure of vegetative propagation (e.g. grafting, budding)

10)10)Suppression effect from treesSuppression effect from trees

INTRODUCTIONINTRODUCTION

• Allelopathy is derived from two Greek words “allelon” Allelopathy is derived from two Greek words “allelon” means “of each other” and “pathos” means “to suffer”, means “of each other” and “pathos” means “to suffer”, and means the “injurious effect of one organism upon and means the “injurious effect of one organism upon the other” the other”

• Hans Molisch (1937)Hans Molisch (1937), plant physiologist, University , plant physiologist, University of Vienna, Austria, coined the term allelopathyof Vienna, Austria, coined the term allelopathy

• It was first reported in alfa-alfa, and the first It was first reported in alfa-alfa, and the first allelochemical was extracted from walnut.allelochemical was extracted from walnut.

• Actually, it is the process involving secondary Actually, it is the process involving secondary metabolites, produced by algae, bacteria, plants , metabolites, produced by algae, bacteria, plants , which influence the growth of the other or same which influence the growth of the other or same species.species.

• The central principle in Allelopathy arises from the fact that plants and microorganisms collectively produce thousands of chemicals, and many of these chemicals are released from the producing organism by leaching, exudation, volatilization, or decomposition processes. Subsequently, some of these compounds (known as allelochemicals) alter the growth or physiological functions of organisms that encounter them during growth.

• For example, almost pure droplets of sorgoleone (a quinone) are exuded from the roots of Sorghum species, which inhibits growth

in plants that contact it by blocking photosynthesis and respiration.

• Cinnamic and benzoic acids, flavonoids , and various terpenes are the most commonly found allelochemicals,. A few allelo-chemicals have been developed as herbicides and pesticides.

Allelopathic ChemicalsAllelopathic Chemicals

• Phenolic acid

• Coumarins – block mitosis in onion by forming multinucleate cells

• Terpinoids • Flavinoids • Scopulatens – inhibits photosynthesis without

significant effect on respiration

Ways of releasing allelochemicals Ways of releasing allelochemicals

Allelopathic chemicals are released from the plants as:

• Vapour – from root and leaf (through stomata)

• Foliar leachate

• Root exudate • Breakdown/ decomposition product of dead plant parts • Seed extract

SOURCES OF ALLELOPATHY

. TYPES OF ALLELOPATHY

True allelopathy Functional allelopathy

Crop against other crops:

Examples:Examples:• Sunflower has been foundSunflower has been found allelopathic to groundnut underallelopathic to groundnut under intercropping situationintercropping situation• Tree crops like Tree crops like EucalyptusEucalyptus also shows some allelopathic also shows some allelopathic

interactions to vegetables and some field crops grown interactions to vegetables and some field crops grown as intercrop with it.as intercrop with it.

• Crop residues of lentil are phytotoxic to wheat and of Crop residues of lentil are phytotoxic to wheat and of sunflower and mustard to several cropssunflower and mustard to several crops

• Sorghum is allelopathic to wheat and sweet potato to Sorghum is allelopathic to wheat and sweet potato to cowpea.cowpea.

• Mung/ green gram and cowpea are stimulatory to the Mung/ green gram and cowpea are stimulatory to the growth of wheat.growth of wheat.

FORMS OF ALLELOPATHIC INTERACTIONS

Crop against weeds: Crop against weeds: Examples:Examples:• Sorghum releases hydrocynic acid (HCN) and suppresses many Sorghum releases hydrocynic acid (HCN) and suppresses many

weeds growing in vicinity. weeds growing in vicinity. • Barley produces “gramine” an alkaloid, which inhibits weed growth Barley produces “gramine” an alkaloid, which inhibits weed growth

S.No. Crops Weed species

1 Maize Chenopodium album, Amaranthus retroflexus

2 Sorghum Setaris viridis, Bromus pectinatus, Amaranthus hybridus

3 Cucumber Echinochloa crusgalli

4 Sweet potato Cyperus rotundus, Cyperus esculentus

Crops Weeds Cause/source released from crop plant

Effect on weeds

Coffea arabica (Coffee)

Amaranthus spinosus (Spiny amaranth)

1,3,7-trimethylxanthin

Inhibit germination

Zea mays (Maize) Agropyron repens Setaria viridis

Increased Catalase and Peroxidase activity by root extract

Inhibit growth

Oat, pea, wheat Chenopodium album (Lamsquarter)

Root exudates Suppress growth

Weed against crops:Weed against crops:S.No. Weeds Crops

1 Cyperus rotundus Sorghum , soybean

2 Imperata cylindrical Several crops

3 Chinopodium album Alfalfa, cucumber, oat, maize

4 Cirsium arvense Several crops

5 Avena fatua Several crops

•

Weeds Crops Cause/source released from weeds

Effect on crops

Agropyron repens (Quack grass)

Maize, potato Ethylene produced by the activity of microorganism on rhizomes of weeds

Decrease uptake of manures (N,K) followed by yield reduction of crop

Avena fatua (Wild oat)

Wheat, barley, oat Root exudates Growth of leaves and roots of wheat

Cynodon dactylon (Bermuda grass)

Barley Decayed grass residues of weeds

Seed germination, root and top growth of crop

Cyperus esculentus (Yellow Nut sedge)

Grain crops, soybean, orchard

Vanillic acid, Hydrobenzoic acid in sedge extract

Root and shoot growth of maize and soybean

Weeds Weeds Cause/source released from weeds

Effect on weeds

Impereta cylindrica (Cogon grass)

Borreria hispada (Button weed)

Exudates of inhibitory substances through rhizomes

Inhibits the emergence and growth

Sorghum halepense (Johnson grass)

Setaria viridis (Giant foxtail), D. sanguinalis (Large crabgrass)

Living and decaying rhizomes and leaves

Inhibit growth

WEEDS AGAINST WEEDS

PLANT CHEMICALS REFERENCES

Secale cereal L.

(Rye)

Avena sativa L.

Sorghum bicolor L.

(Sorghum),

Barley

Mungbean

Medicago sativa L.

Chenopodium

Cucumis sativus L. (Cucumber)

2,4-dihydroxy-1,4(2H)benzoxazin-3-

one (DIBOA) 2(3H)-

benzoxazolinone (BOA)

Ferulic acid

P-cumaric acid

Hydroxamic acid

Saponins

Ascaridole, alpha-terpinene

Gamma-linolenic acid,

Alpha-asarone

Benzoic and Cinnamic acids

Barnes & Putnam (1987)

Rice (1984)

Perez ( 1990)

Corcurea et al. (1992)

Krol et al. (1995)

Corcurea et al. (1992)

Yu and Matsui, 1994

Crops Weeds Allelochemicals Referrences

Rice Echinochloa colona

Phenolic acids Rimando et al., 2001

Wheat Avena fatua Hydroxamic acids Niemeyer, 1988

Cucumber Impereta cylindrica Benzoic and Cinnamic acids

Yu and Matsui, 1994

Black mustard Phalaris paradoxa Allyl isothiocyanate Weston, 1996

Buck wheat Canada thistle Fatty acids Weston, 1996

Clovers and Sweet clover

Echinochloa crusgalli

Isoflavonoids andPhenolics

Weston, 1996

Oat Chenopodium album

Phenolic acids& Scopoletin

Weston, 1996

Cereals Hydroxamic acids Weston, 1996

Sudangrass - Phenolic acidsand Dhurrin

Weston, 1996

Sorghum Echinochloa colona

Sorgoleone Netzley and Butler(1986)

AJEA,2010

Factors affecting Allelopathic effect Factors affecting Allelopathic effect

• Allelopathic effects might also depend on a number of other factors that might be important in any given situation:

• VarietiesVarieties:: There can be a great deal of difference in the strength of allelopathic effects between different crop varieties.

• SpecificitySpecificity: There is a significant degree of specificity in allelopathic effects. Thus, a crop which is strongly allelopathic against one weed may show little or no effect against another.

• AutotoxicityAutotoxicity:: Allelopathic chemicals may not only suppress the growth of other plant species, they can also suppress the germination or growth of seeds and plants of the same species. Lucerne is particularly well known for this and has been well researched. The toxic effect of wheat straw on following wheat crops is also well known

• Crop on crop effectsCrop on crop effects: Residues from allelopathic crops can hinder germination and growth of following crops as well as weeds. A sufficient gap must be left before the following crop is sown. Larger seeded crops are effected less and transplants are not affected.

• Environmental factorsEnvironmental factors: Several factors impact on the strength of the allelopathic effect. These include pests and disease and especially soil fertility. Low fertility increases the production of allelochemicals. After incorporation the alleopathic effect declines fastest in warm wet conditions and slowest in cold wet conditions.

CONCLUSION• Allelopathy plays an important role in investigations of appropriate

farming systems as well as in the control of weeds, diseases and insects, the alleviation of continuous cropping obstacles, and allelopathic cultivar breeding.

• Furthermore, allelochemicals can act as environmentally friendly

herbicides, fungicides, insecticides and plant growth regulators, and can have great value in sustainable agriculture.

• With increasing emphasis on organic agriculture and environmental protection, increasing attention has been paid to allelopathy research, and the physiological and ecological mechanisms of allelopathy are gradually being elucidated. It is obvious that allelopathy requires further research for widespread application in agricultural production worldwide.

ReferencesReferences

• Abrahim D., Takahashi L., Kelmer-Bracht A. M., Ishii-Iwamoto E. L. (2003b). Effects of phenolic acids and monoterpenes on the mitochondrial respiration of soybean hypocotyl axes. Allelopathy J. 11, 21–30

• Anaya A. L. (1999). Allelopathy as a tool in the management of biotic resources in agroecosystems. Crit. Rev. Plant Sci. 18, 697–739. 10.1080/07352689991309450

• Belz R. G. (2007). Allelopathy in crop/weed interactions–an update. Pest. Manag. Sci. 63, 308–326. 10.1002/ps.1320

• Bhadoria P. (2011). Allelopathy: a natural way towards weed management. Am. J. Exp. Agric. 1, 7–20