Article Type: Review Several sources reported the advantages of synthetic fungicides in boosting food production. However, there are serious concerns and negative consequences associated with their use on ecological and human health in recent years. Besides, pathogens’ resistances to some of the most effective fungicides have been reported. These amongst other drawbacks prompted the search for alternatives. Plants offer an expanse of exploitable chemical space in this regard which is unparalleled in nature and not beaten by combinatorial chemistry as yet. Extracts of higher plants have demonstrated a wide range of activity against plant pathogenic organisms. These plants extracts have been found to contain broad spectra of phytochemicals (secondary metabolites) such as alkaloids, flavonoids, tannins, saponins, phenols, glycosides, terpenoids, phlobatannins, polyphenols and steroids. Secondary metabolites constitute plants’ weaponry against pests and pathogens invasion. These groups of phytochemicals possess wide ranging chemical functional groups; by which they establish contact with and bind to sites on target pathogens to ineffectuate them. Complexes of these secondary metabolites occur in crude extracts. Need therefore arises in the present to identify, isolate and purify the active secondary metabolite(s) in the crude extracts and to determine the one(s) effecting the reported kills and fungitoxity of the extracts. With the exception of neem assertive reports on the modes of action of most bioactive secondary metabolites are unavailable. We have to understand the functional groups of the bioactive phytochemical isolates, their position on the carbon skeleton of the principles, their binding sites on target pathogenic species; and the metabolic process(es) which they affect and ineffectuate. This will aid in either synergizing or synthesizing them so as to combat the enormous and obvious challenges of fungicide resistance threatening agricultural production and food security. This work reviews available literature in these regards. ©2013 BluePen Journals Ltd. All rights reserved

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Significance of characterization of secondary metabolites from extracts of higher plants in plant disease management

Antifungal effects of Rhus coriaria L. fruit extracts against tomato anthracnose caused by Colletotrichum acutatum

Objective: Present study is focused on development of EC (Emulsifiable Concentrate) from extract of aerial part of Ageratum conyzoides Linn and evaluation of antimicrobial activity of crude extract and developed formulation. Studies of physico-chemical parameter of crude extract (methanolic) and developed formulations was carried out for standardization of crude extract as well as developed formulation. Extraction from the aerial parts of plant using different solvents were done. Development of Emulsifiable Concentrate (EC) formulations from the crude extracts using non-toxic solvents and emulsifiers and studies of their physico-chemical parameters were carried out. Comparative antimicrobial study of crude extracts and developed formulations were also done. Methods: Extraction from the aerial parts of Ageratum conyzoides was done using different solvents like dichloromethane, methanol and hexane. Physico-chemical parameters of methanolic crude extract like loss on drying (LOD), total ash, acid soluble ash, etc. have been studied. Analysis of each crude extract (extract of methanol, dichloromethane and hexane) by HPTLC (High Performance Thin Layer Chromatography) and GC- MS (Gas Chromatography-Mass Spectrophotometry) for confirmation of bioactive compound was done. Emulsifiable concentrate (EC) was developed using bio-degradable solvents and emulsifiers. Physico-chemical parameters of these ECs were studied as per standard method. Comparative antimicrobial activity of crude extracts and developed formulations were done against Escherichia coli and Staphylococcus aureus bacteria and Candida albicans fungus. Results: The GC- MS analysis result showed presence of bioactive compounds in each extract where as HPTLC showed maximum elution of components in toluene: ethyl acetate (9:1) solvent system. Developed ECs were found much more active against bacteria and fungi than crude extracts. Conclusion: Developed formulations from aerial part of plant were found to have better antimicrobial activity than their crude extracts which can be tried in medicine formulations though lot of work is yet to be done. Physicochemical parameters and HPTLC studies were done to authenticate the adulteration for quality control of plant extracts and their formulation.

Formulation development, standardization and antimicrobial activity of ageratum conyzoides extracts and their formulation

Zizyphus spina-christi L. has antimicrobial properties because of the presence of biologically active compounds. Alternaria is an opportunistic pathogen that causes leaf spots, rots, and blights on a variety of plant parts. This study aimed to reduce the usage of synthetically derived fungicides. Identification of the bioactive components present in leaves and fruits methanolic extracts of Z. spina-christi was performed using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The efficacy of the two methanol extracts was tested against (a) in vitro fungal growth and (b) pathogenicity control on non-wounded and wounded tomato fruits. The results revealed that gallic acid and ellagic acid were the major components in leaves extract while quercetin was the major component in fruits extract. In addition, Phenol, 2,5-bis(1,1-dimethylethyl) (40.24%) and Decane, 2-methyl-(18.53%) were the most abundant components in the leaf extract, and the presence of D-mannonic acid, 2,3,5,6-tetrakis-o-(trimethylsilyl), and γ-lactone (22.72%) were major components in fruits extract. The methanolic extracts of Z. spina-christi leaves and fruits demonstrated significant antifungal activity against the growth of Alternaria alternata, A. citri, and A. radicina with variable inhibition percentages at different concentrations. Pathogenicity was increased when the skin was injured, as expected. Both extracts reduced the percentage of infected fruits.

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Bioactive Compounds and Antifungal Activity of Leaves and Fruits Methanolic Extracts of Ziziphus spina-christi L.

Pythium species are morphologically polymorphic, physiologically unique and ecologically versatile, which make them significant both theoretically and practically. They are ubiquitous in soil and in water, distributed worldwide, and with very diverse host ranges. They include some of the most important and destructive plant pathogens, causing losses of seeds, pre-emergence and post-emergence damping-off, rots of seedlings, roots, basal stalks, decays of fruits and vegetables during cultivation, storage, transit or at the market, and cause serious damage of a wide variety of crops. The most aggressive species of Pythium that cause important plant diseases is P. aphanidermatum. It is a soil as well as seed born pathogen. The chemical fight and physical control of this fungal pathogen are very difficult to realize and in view of its broad host range, crop rotation also not completely control the pathogen. Moreover, use of chemicals to control the disease is also criticized throughout the world due to its detrimental effects on environment, as they are harmful for human and animal health as well as soil. Besides this, P. aphanidermatum became resistant to the common fungicides used against it. Eventually, it has forced scientist to find out the best alternatives to control this notorious pathogen. Hence here in this review paper the different control measures as well as use of plant extracts used against Pythium by researchers and many workers is summarized in brief.

http://www.ijpaes.com/admin/php/uploads/781_pdf.pdf

Review article PYTHIUM DISEASES, CONTROL AND MANAGEMENT STRATEGIES: A REVIEW

The present study was undertaken to determine the effect of some medicinal plants on growth parameters and diseases, like alternaria canker, blight, leafspot, fruitspot, blossom end rot and sunscald of Lycopersicum esculentum. To understand the mechanism, the phytochemical analysis of plants and its effect on bacterial and fungal cultures were investigated. The effects of selected plant extracts on tomato were observed. Ten medicinal plants were applied for the control of diseases, and its antibacterial and antifungal effect was tested against Clavibacter michigenesis, Alternaria solani, and Septoria lycopersici, Pythium debaryanumand and Phytopthora capsici that cause alternaria canker,early blight, leaf spot, fruit spot, blossom end rot and sunscald disease in Lycopersicum esculentum..Extract of Ageratum.conyzoides was efficient in inhibiting the growth of Clavibacter michigenesis while mycelial growth of Alternaria solani,Septoria lycopersici,Pythium debaryanum & Phytopthora capsici was inhibited by Tagetes patula, Piper nigrum, Aegle marmelos & Ageratum conyzoides.Among the plant extract tested in field, Ageratum.conyzoides was found most effective in reducing the Alternaria canker disease by 78.20% and Azadirachta.indica reduced the Early blight & leaf spot disease by 53.84% & 40.78%respectivilly,Aegle marmelos reduced the fruit spot disease by 61.29%.Pongamia pinata & Brassica campestris reduced the Blossom end rot disease by 86.95% and 82.17% and Ageratum.conyzoides& Pongmia pinata reduced the sunscald disease by90.08% & 76.85% respectively in Lycopersicum esculentum. The result suggests the applications are also growth promotive and cost effective and non-hazardous in agro-ecosystem.

https://www.imedpub.com/articles/bioefficacy-of-some-plant-extracts-on-growth-parameters-and-control-of-diseases-in-lycopersicum-esculentum.pdf

Mitali Madhusmita Pattnaik

Papers

Bioefficacy of some plant extracts on growth parameters and control of diseases in Lycopersicum esculentum