Research on the control of plant diseases by phyllosphere applied biological control agents has produced a wealth of informations on a wide range of fungal and bacterial biocontrol agents and their applications for controlling diseases affecting leaves, flowers and fruits. Research into their mode of action and ecological adaptation has provided critical insights that have increased commercial utilization of phyllosphere applied biocontrol agents has proven to be challangeing because the leaf surface presents a relatively hostile environment for introduced microbes with a relative paucity of available nutrients, wide water availability fluxes, direct exoposure to ultraviolet radiation and infrared radiation and competition with other phyllosphere colonist.
Foliar applied biocontrol agents do not have the avoidance strategy of endophytic growth available to pathogens and therefore must primarily utilize a tolerance strategy whereby they colonise and survive on the leaf surface or in protected sites that may or may not be the same as the pathogen they are intended to control. Because of the variable effects of the biological and physical environment, the vast majority of phyllosphere applied biocontrol agents research has been focused on glasshouse or storage environment wherethe physical environment is more predictable and stable.
Many of the early studies aimed at the study of the mode of action and evaluation of the efficacy of some potential biocontrol bacteria, such as Brevibaccilus subtilis, producer of antibiotics, however, the application of such bacteria on fruit did not prove to be commercially acceptable. Wilson and Wisniewski indicated the following characteristics of an ideal antagonist: genetic stability, efficacy at low concentrations and against a wide range of pathogens on various fruit products, simple nutritional requirements, survival in adverse environmental conditions, growth on cheap substrates in fermenters, lack of pathogenicity for the host plant and no production of metabolites potentially toxic to humans, resistance to the most frequently used pesticides and compatibility with other chemical and physical treatments. Yeasts seem to possess a good number of the above mentioned features and during the last few years, research has been made on the selection and study of yeasts.
Table of Contents
1. Against Colletotrichum musae
2. Against Rhizoctonia solani
3. Against Alternaria solani
4. Against Fusarium oxysporum f.sp.ciceri
Research Objectives and Topics
The primary objective of this study is to evaluate the antagonistic efficacy of 38 distinct yeast isolates against four major post-harvest plant pathogenic fungi (Colletotrichum musae, Alternaria solani, Rhizoctonia solani, and Fusarium oxysporum f.sp.ciceri) using an in-vitro dual culture assay on modified PDA medium.
- Screening of yeast isolates for biocontrol potential against post-harvest pathogens.
- Assessment of growth inhibition percentages in dual culture plates.
- Development of a modified culture medium to support both yeast and pathogen growth.
- Categorization of antagonistic potential into low, medium, and high efficacy groups.
- Observation of fungal morphological changes and suppression mechanisms in the presence of antagonistic yeasts.
Excerpt from the Book
Introduction:
Research on the control of plant diseases by phyllosphere applied biological control agents has produced a wealth of informations on a wide range of fungal and bacterial biocontrol agents and their applications for controlling diseases affecting leaves, flowers and fruits. Research into their mode of action and ecological adaptation has provided critical insights that have increased commercial utilization of phyllosphere applied biocontrol agents has proven to be challangeing because the leaf surface presents a relatively hostile environment for introduced microbes with a relative paucity of available nutrients (Beattie and Lindow,1999;Beattie,2002), wide water availability fluxes (Beattie and Lindow,1995), direct exoposure to ultraviolet radiation(Sundin,2002) and infrared radiation and competition with other phyllosphere colonist.
Foliar applied biocontrol agents do not have the avoidance strategy of endophytic growth available to pathogens (Beattie and Lindow,1995) and therefore must primarily utilize a tolerance strategy whereby they colonise and survive on the leaf surface or in protected sites that may or may not be the same as the pathogen they are intended to control. Because of the variable effects of the biological and physical environment, the vast majority of phyllosphere applied biocontrol agents research has been focused on glasshouse or storage environment wherethe physical environment is more predictable and stable (Paulitz and Belanger,2000).
Summary of Chapters
1. Against Colletotrichum musae: This chapter details the screening of yeast isolates against the banana anthracnose pathogen, identifying Y22 and Y4 as highly effective strains.
2. Against Rhizoctonia solani: This section reports on the inhibition of this soil-borne sclerotial fungus, noting Y7 as the most potent antagonist among the tested samples.
3. Against Alternaria solani: The chapter presents the results of growth inhibition for this widespread pathogen, highlighting Y49 as the most effective yeast isolate.
4. Against Fusarium oxysporum f.sp.ciceri: This final chapter discusses the in-vitro suppression of the wilt pathogen, finding that while several isolates showed moderate inhibition, no single isolate exceeded 50% inhibition.
Keywords
dual culture technique, antagonistic yeasts, bio-control efficiency, plant pathogenic fungi, Colletotrichum musae, Rhizoctonia solani, Alternaria solani, Fusarium oxysporum f.sp.ciceri, phyllosphere, post-harvest disease, growth inhibition, biocontrol agents, in-vitro, radial growth, pathogen control.
Frequently Asked Questions
What is the primary focus of this research?
The work focuses on the in-vitro evaluation of 38 yeast isolates to determine their potential as biological control agents against four specific post-harvest fungal pathogens.
What are the central thematic fields covered?
The paper covers agricultural biotechnology, specifically plant pathology, biological control, fungal inhibition, and microbial screening for post-harvest disease management.
What is the main objective of the study?
The objective is to identify and categorize yeast isolates based on their ability to inhibit the radial growth of pathogens in dual culture experiments.
Which scientific method is employed?
The study utilizes a dual culture technique on a modified potato dextrose agar (PDA) medium, supplemented with yeast extract to facilitate the growth of both yeasts and pathogens.
What topics are discussed in the main body of the work?
The main body presents experimental results for each of the four pathogens, including inhibition percentages, radial growth observations, and summaries of the antagonistic potential of each yeast isolate.
Which keywords best characterize this work?
Key terms include dual culture technique, antagonistic yeasts, biocontrol efficiency, post-harvest pathogens, and specific fungal names like Colletotrichum musae.
Why was it necessary to modify the PDA medium?
Standard PDA was suitable for the fungi but insufficient for the growth of the isolated yeasts; therefore, 1% yeast extract was added to provide essential growth factors for both organisms.
What are the characteristics of the most successful antagonist, Y7, against Rhizoctonia solani?
Y7 was isolated from date palm wine and is described as having a creamish, smooth, and fast-growing nature, likely employing antifungal metabolites, space competition, and mycoparasitism.
How does the pathogen behavior change in the presence of effective yeast isolates?
Observations showed growth suppression, hyphal dissolution, and in some cases, swelling and development of irregular septation in the inhibited hyphae compared to normal conditions.
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- Prasad Singha (Autor:in), Dharnendra Reang (Autor:in), Mayanglabambam Ranjana Devi (Autor:in), 2010, "In-vitro" Evaluation of Antagonistic Potentials of Some Yeast Isolates Against Different Plant Pathogenic Fungi, München, GRIN Verlag, https://www.grin.com/document/380446
