Phytoalexins ptt by AARIF

Phytoalexins ptt by AARIF

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  Presented By; Aarif Maqbool M.Sc4th Sem. Roll No. 01 SCHOOL OF STUDIES IN BOTANY JIWAJI UNIVERSITY, GWALIOR (M.P) Paper code: 403 Session 2016-17 Guided by; Dr. Sapan Patel
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  CONTENTS  Introduction.  Phytoalexinsas defence system.  Concept of Phytoalexins.  Mechanism (Action of phytoalexins).  Synthesis of Phytoalexins.  Types of Phytoalexins.  Functions of Phytoalexins.  Conclusion.  Refrences.
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   Phytoalexins aredefined as "low molecular weight, antimicrobial compounds that are both synthesized and accumulated in plants after exposure to microorganisms or abiotic agents''  The term phytoalexin is derived from Greek word- phyto meaning plant and alexin means warding off compound INTRODUCTION  The concept was formalized by Müller & Börger (1941)  Müller (1958) demonstrated the detection of a chemical entity as a phytoalexin while working with the hypersensitive response of bean tissue to the soft-fruit pathogen Monilinia fructicola.
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  PHYTOALEXINS DEFENCE SYSTEM PRE -EXISTINGPOST EXISTING STRUCTURAL BIOCHEMICAL PHYTOALEXINS
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  CONCEPT OF PHYTOALEXINS Mueller and Borger concept of Phytoalexins and their conclusions :  a) phytoalexin is formed only when the host cells come into contact with the parasite.  b) the defence reaction occurs only in the living cells.  c) the inhibitory material is a chemical substance & may be regarded as a product of necrobiosis of the host cell.  d) phytoalexin is non-specific in its toxicity.  e) the resistant state is not inherited.  f) the defence reaction is confined to the tissue colonized by the fungus and its immediate neighbourhood.
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  SYNTHESIS OF PHYTOALEXINS Hostplant surface+ water Diffusion of host nutrients Host lechates +Fungal spores Germination & growth of fungus Mycoantigen +viable host cells Stimulation of host metabolism Production of phytoalexin
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  MECHANISM; (ACTION OFPHYTOALEXINS)
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  TYPES OF PHYTOALEXINS Ipomoeamarone;Sesquiterpinoid induced in sweet potato tissue infected with black rot fungus Ceratocystis fimbriata. Inhibitory effect on the fungus even at 0.1% concentrations. Pisatin; It is a phenolic ether having chromocoumarin ring. Produced by the exposed endocarp of the detached pea in response to inoculation with many fungi or injury. Production of pisatin by pea pods inoculated with Monilia fructicola . It is a weak antibiotic with broad spectrum activity Source; https://pubchem.ncbi.nlm.nih.gov Ipomoeamarone Pistan
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  Phaseollin: It issimilar to pisatin in chemistry and function prduced by beans. It is fungicidal at high concentrations and fungistatic at low concentrations against Sclerotinia fructigena. Isocoumarin: isolated from carrot root tissues inoculated with a fungus non-pathogenic to carrot, Ceratocystis fimbriata ,chemically related to the pterocarpan phaseollin Source; https://pubchem.ncbi.nlm.nih.gov Phaseollin Isocoumarin
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  Trifolirhizin: It isa glucoside which has been isolated from the roots of red cloves. Its structure indicates that it is chemically closely related to pisatin. Rishitin: Muller and Boerger(1940) were the first to show that the potato tubers carying the gene R1 for late blight resistance responded when inoculated with avirulent race of P.infestans by producing a phytoalexin that inhibited the development of a virulent race. Source; https://pubchem.ncbi.nlm.nih.gov Trifolirhizin Rishitin
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  Gossypol: It isan ether soluble phenol produced by cotton . It is also produced in diseases like black spot of rose(Diplocarpon rosa),leaf spot of wheat (Septoria tritici). Xanthotoxin: Isolated from parsnip root discs inoculated with C.fimbriata inoculation with other non pathogens resulted in production of xanthotoxin Capsidiol: it is a sesquiterpene phytoalexin produced in pepper fruits inoculated with fungi. Produced concentrations are sufficient to inhibit these fungi in vitro. Source; https://pubchem.ncbi.nlm.nih.gov Gossypol Xanthotoxin Capsidiol
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  Source; https://pubchem.ncbi.nlm.nih.gov Medicarpin Glyceollin Medicarpin:Alfalfa (Medicagosativa) inoculated with a series of pathogens and non pathogens have been studied. The antifungal compound was isolated and identified as Medicarpin. Glyceollin: produced in soybean plants infected with the fungus Phytophthora megasperma.
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  FUNCTIONS OF PHYTOALEXINS Phytoalexins produced in plants act as toxins to the attacking organism.  They may puncture the cell wall.  Delay maturation, disrupt metabolism or prevent reproduction of the pathogen.  Their importance in plant defense is indicated by an increase in susceptibility of plant tissue to infection.  They show defence reaction only in living cells.  They can't be inherited.
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  CONCLUSION  Phytoalexins areonly one components of the complex mechanisms for disease resistance in plants  Phytoalexins tend to fall into several classes including terpenoids, glycosteroids and alkaloids.  They act against fungi pathogens espacially.  They are synthesized de novo by plants that accumulate rapidly at areas of pathogen infection.  Health promoting effect.  They have susceptible host and present in living cells only.
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  REFRENCES  Mehrotra RS '' Plant Pathology '' First Edition (1980), Tata McGraw Hill Publishing Company limited, New Delhi.  Panday B P " Plant pathology (pathogen and palant diseases) '' First Edition (1982) , S.Chand publication ,New Delhi.  Yadav Dinesh Kumar "Plant Pathology"First Edition (2013), Shree Publishers and Distributors, New Delhi.  http://bcs.whfreeman.com/webpub/Ektron/Hillis%20Principles%20of %20Life2e/Animated%20Tutorials/pol2e_at_2801_Signaling_between_ Plants_and_Pathogens/pol2e_at_2801_Signaling_between_Plants_and Pathogens.html