Role of fungi as biocontrol agents

In this slide different fungi are Mentioned and their role as bio-control agents is also elaborated which is reviewed from different research articles cited in reference portion.

1. Muhammad Anwaar Ul Haq F16-BSBT-011 Contact Number : [phone] [email protected] Role of Fungi As Biocontrol Agents for the Control of Plant Diseases BS-Biotechnology Group- ll Fungal Biotechnology Instructor: Dr. Shumaila Sikandar

2. Biological control is the process which decreases the inoculum density of the pathogenic microbes, present in dormant state by the other microbes. Generally, it involves either the naïve or genetically modified microbes which reduce the effect of pests, pathogen, and diseases. The plant disease is controlled by the pesticides, which are now extensively used. Due to excessive use of pesticides, socioeconomic and environmental pollution issues have been resulted, which demand the alternative method to reduce content of chemical pesticides. Biological control is an eco-friendly method employed to control the plant diseases, with the aim of developing a sustainable system in agriculture. Biological control mecha - nism involves the interaction among the antagonists and pathogens , which aid in selection and manipulation to develop an effective control system. Currently, this approach is employed when no other alternative is available. Emergent of fungal antagonistic has made it a promising biological control strategy to control the plant diseases. Introduction

3. Cont … Biological control is the process which reduces the number of microbes or patho - gens by other microorganisms, without the external intervention of humans (Cook and Baker 1983 ). In 1967 , Beirner stated that biological control is the controlling of one microbe by the other. This can be stated either as a large community of pest ( DeBach 1964 ) or as an inhibitor of severe pest damage irrespective of the pest inhabitants (Cook and Baker 1983 ). It largely depends on the understanding of biological interactions with ecosystem and microbes up to cellular and molecular level, which are more complex and difficult to control in comparison to physical as well as chemical methods. Additionally, this method is a highly stable and long- lasting process (Baker and Cook 1974 ). This method is claimed to be a valuable alternative approach to regulate the plant diseases , in which one microbe inhibits the proliferation and infection caused by the other microbes (Cook 1993 ; Baker 1987 ). Being an eco-friendly approach, thus in few cases, this approach is predominantly used to save the plant from pathogenic microbes (Cook 1993 ). The approach employs natural predators which have the ability to eradicate and control the growth of pest as well as pathogens. This method explores the antagonism potential of microbes, which makes it an eco-friendly approach to control the plant disease. Thus, by calculating the cost of hazardous pesticides and other chemical agents, biological control is an efficient and eco-friendly method for controlling plant dis- eases, which can be used worldwide.

4. Significance of Biological Control   Biological control provides protection to the plant throughout its cultivation period. The biological agents proliferate rapidly in soil and leave no residue. Being non- toxic, it is safer for humans and plants . This approach is not limited for controlling the disease; additionally, it also enhances the growth (especially root) and yield of the crop . Due to easy handling and manufacturing , it can be used in combination with bio-fertilizers. Moreover, it is a cheap, safe , and eco-friendly method.

5. Importance of Biological Control Chemical pesticides were used to enhance crop yield, but extensive use affects the nontargeted organism and surrounding environment. Thus, the current scenario demands the eco-friendly approach for controlling the pest, as chemical pesticides being not suitable for cultivation of crop. Bacteria, fungi, nematodes, protozoans, and virus have been extensively studied because of advantageous characteristics. Overexploitation of fungicides has resulted in gathering of the toxic molecules which are harmful to the environment and humans, but pathogenic microbes have adapted themselves by getting resistant to it. In order to overcome this global prob- lem related to chemical control, alternative approaches are being exploited. Additionally, this biological control approach is highly effective for sustainable agriculture and is a vital component of integrated pest management (IPM) program.

6. Microbial Biocontrol Agents   Aspergillus spp., Ampelomyces sp., Candida sp., Coniothyrium sp., Gliocladium sp., and Trichoderma spp. are fungal. Among them, the most versatile fungal agent belongs to Trichoderma sp. for controlling the growth of pathogenic fungi. Presently, commercial Trichoderma products are used as biopesti - cides which amend the soil and increase the plant growth. In 1934, Weindling showed the bio- control potential of Trichoderma lignorum ( viride ) against Rhizoctonia solani , a fungal pathogen. Further, Trichoderma lignorum ( viride ) also showed mycoparasitic activity against Phytophthora , Pythium , Rhizopus , and Sclerotium rolfsii (Wells 1988 ).

7. Efficacy of Microbial Biocontrol Agents   In addition to properties discussed above, there are few amendments which enhance the efficiency of this method. First, inappropriate usage of this technique should be prevented, which is mostly because of improper knowledge. Second, one should be able differentiate failure which is cause by low-quality inoculum Moreover, inefficacy occurs because the compost/fertilizers containing biocontrol agents are not of superior quality as available in registered plant products. To improve the efficiency of the biocontrol agents, the strain should be assessed and verified against the tar- geted disease plus optimum condition should also be noted. Specific substrates and carriers also aid in enhancing the efficacy of the agents. Exploration of effective strains will also improve the quality of biocontrol agents and lessen the required amount.

8. Mass Production of Biocontrol Agents   Mass production of the biocontrol agents is required to meet the commercial demand. There is no effective method for the mass production of these biocontrol agents at industrial level, as the production of these biocontrol agents requires continuous resource which should be readily available. Trichoderma spp . have been reported to grow on various solid substrates such as coffee husk, saw dust, sorghum grain, waste of tea leaf, wheat grain and bran, etc.

9. Commercial Products of Biocontrol Agents Commercially available biocontrol products which control the plant disease are a new prospect. But it started in 1979, when Agrobacterium radiobacter strain K 84 was enlisted in EPA (United States Environmental Protection Agency) list for controlling crown gall disease in plant. Later on, Trichoderma harzianum ATCC 20476,the first fungal strain, was enlisted in EPA list for controlling the plant diseases. Presently , 12 fungi strains have been recorded by EPA which aid in controlling the plant disease ( Fravel 2005). The majority of these biocontrol agents are commercially marketed .

10. Fungi as biocontrol agent Fungi possess a number of characteristics that make them potentially ideal bio control agents. Firstly, many saprophytic species antagonize, representatives of all the pest organisms, including plant pathogenic fungi, weeds and insects. Secondly, fungi can be readily grown in culture so that large quantities can be economically produced for release, mainly as spores or mycelial fragments, into the environment. These inoculants then germinate or grow to produce active mycelium which can parasitize or otherwise inhibit the pest without damaging the non-target organisms. Fungi also survive for relatively long periods as resting bodies, and can then germinate to grow and control the target population thereby making continual re-inoculation with the bio-control agent unnecessary.

11. Example of Bio Control Agents Used  Commercially: 1 . Trichoderma harzianum —White rot onion 2. Phlebia gigantean — Heterbasidion root rot pine 4. Sporidesmium sclerotivorum —Lettuce drop lettuce 5. Talaromyces flavus — Damping off sugarbeet .

12. Reduce the negati v e e f fects of plant p a tho ge ns and pro m ote positive responses in plant. Inoc u lated plants are sens i t ized t o re spond m ore rapidly to pathogen attack Alleviation of abiotic stresses Improve photosynthetic efficiency, especially in plants subjected to various stresses Increase nutrients absorption and nitrogen use efficiency in plants Enhance the growth and yield parameters Role of BCF’s 13

13. Fungal compounds involved in induction of plant responses Compounds that are released by Trichoderma spp . into the zone of interaction induce resistance in plants Primarily proteins with enzymatic activity xylanase, cellulase, swollenin and endochitinase Enhance defense, through induction of plant defense–related proteins and peptides that are active in inducing terpenoid, phytoalexin biosynthesis and peroxidase activity.

14. Mechanisms of Fungal Biocontrol Agents 15

15. Type Mechanism Examples Direct antagonism Hyperparasitism /predation Lytic/some nonlytic mycoviruses Ampelomyces quisqualis Lysobacter enzymogenes Pasteuria penetrans Trichoderma virens Mixed-path antagonism Antibiotics 2,4-diacetylphloroglucinol Phenazines Cyclic lipopeptides   Lytic enzymes Chitinases Glucanases Proteases   Unregulated waste products Ammonia Carbon dioxide Hydrogen cyanide   Physical/chemical interference Blockage of soil pores Germination signals consumption Molecular cross-talk confused Indirect antagonism Competition Exudates/leachates consumption Siderophore scavenging Physical niche occupation   Induction of host resistance Contact with fungal cell walls Detection of pathogen-associated, molecular patterns Phytohormone -mediated induction

16. Mycoparasitism The term mycoparasitism or "hyperparasitism" has been used to indicate the interrelationships of a parasite and a fungus host. The term mycoparasite refers to organisms that have the ability to parasite fungi, and mycohost means the fungi act as host to be parasitized

17. “ Interactions that involve a low- molecular weight compound or an antibiotic produced by microorganism that has a direct effect on another microorganism” Antibiosis

18. Competition Competition for nutrient and space. Biocontrol agent decreases the availability of a particular substance thus limiting the growth of the plant pathogenic agents Trichoderma spp produce siderophores that chelate iron and stop the growth of other fungi

19. Applications In Plant Disease Control 20

20. Coniothyrium minitans Sclerotinia blight , caused by the soilborne fungus Sclerotinia minor Jagger , is an important disease of peanut During favorable conditions for Sclerotinia blight , peanut farmers can lose up to 50% yield as a result of the disease. Fungicides for control of Sclerotinia blight alone can cost producers as much as $104 per hectare for a single application, with up to three applications made in a season. Consequently, there is a pressing need to reduce the cost of managing Sclerotinia blight . A number of microorganisms have been reported to parasitize sclerotia of Sclerotinia spp., including Coniothyrium minitan s .

21. Gliochdium virens The efficacy of Gliochdium virens (G 1 and G 2) and Trichoderma longibrachiatum (T 1 and T 2) as biocontrol agents of economically important soil-borne plant pathogens Rhizoctonia solani , Sclerotium rolfsii and Pythium aphanidermatum has been investigated. The G. virens isolate G 1 yielded remarkable protection against groundnut root rot (74.4 %), cotton (66.4 %) and tomato (58.4 %) damping-off but only moderately reduced (36 %) the groundnut stem rot incidence, whereas G 2 was much less effective. Of the two T. longibrachiatum isolates, T 1 was more potent against groundnut root rot (65.6 %) while against tomato damping-off, T 2 conferred greater protection (49.2 %).

22. Trichoderma species Trichoderma species reduces the growth of all the four soil borne pathogens: Sclerotium rolfsii , Fusarium solani , Rhizoctonia solani and Sclerotionia sclerotiorum significantly in different level and, therefore, can be incorporated for integrated disease management of soil borne plant pathogens. Hence, Trichoderma species can be used as a potential biocontrol agent against these pathogens. However, its efficacy against Sclerotium rolfsii (a fungal Plant pathogen in tobacco plant) was found to be more in comparison to others. Trichoderma sp. was found to be effective against Sclerotium rolfsii causing the damping-off, root rot, and seed rot disease in mung bean and sunflower , and moreover, it also increased the plant growth.

23. Trichoderma species Commercial Application Several strains of Trichoderma are commercially available to control plant disease in environmentally friendly agriculture. Fungal Formations TUSAL made from T. harzianum and T. viride cultures to prevent the growth of pathogen soilborne fungi responsible for leaf-falling disease in several crops

24. Paecilomyces lilacinus and Glomus fasciculatum Root-knot nematode ( Meloidogyne incognita ) is a limiting factor causing yield reduction in FCV tobacco crop . As an alternative to nematicides of chemical origin, beneficial fungi such as Paecilomyces lilacinus and Glomus fasciculatum significantly reduced the number of egg masses/g root and final soil nematode population.

25. Ampelomyces quisqualis ( Deuteromycetes ) The fungus  Ampelomyces quisqualis  is a naturally occurring hyperparasite of powdery mildews . It infects and forms pycnidia (fruiting bodies) within powdery mildew hyphae, conidiophores (specialized spore-producing hyphae), and cleistothecia (the closed fruiting bodies of powdery mildews). This parasitism reduces growth and may eventually kill the mildew colony .

26. E ntomopathogenic Fungus An entomopathogenic fungus is a fungus that can act as a parasite of insects and kills or seriously disables them. Since they are considered natural mortality agents and environmentally safe, there is worldwide interest in the use and manipulation of entomopathogenic fungi for biological control of insects and other arthropod pests. In particular, the asexual phases of Ascomycota (Beauveria spp., Lecanicillium lecanii, Metarhizium spp., Paecilomyces spp. and others) are under intense scrutiny due to the traits favouring their use as biological insecticides.

27. Use of Fungi to Control Nematodes: Fungi that parasitise nematodes ( nematophagus fungi) can be divided into nematode- trapping fungi, endoparasitic species and fungi that parasitise nematode eggs. Nematode trapping fungi capture nematodes with specialized structures such as constrictive and non-constrictive rings, adhesive knobs or, lastly, by producing an adhesive material along the entire mycelial surface. Endoparasitic nematophagous fungi live in soils where they produce adhesive spores. These become attached to body of the nematode, on germination, a germ tube enters the body where it grows and consumes the host. Egg parasites, as their name suggests, are nematophagous fungi that parasitise the eggs of nematodes.

28. Use of Fungi to Control Insect Pest: Over 400 species of fungi attack insects and mites, so there is great potential for the use of these organisms as biological insecticides. As insect bio control agents, fungi are markedly superior to other microorganisms because they are generally non-specific in their action and are useful against a wide range of insect pests. Most of the so-called entomopathogenic fungi are phycomycetes and Deuteromycetes . Spores of these fungi attack either the external or gut cuticle of their insect hosts. They then germinate and hyphae penetrate the haemocoel . Death may result from the production of a toxin by the fungus.

29. B eauveria bassiana , Introduction Is a fungus Grows naturally in soils throughout the world and acts as a parasite on various arthropod species, Causes white muscardine disease in silkworms mostly Belongs to the entomopathogenic fungi. It is being used as a biological insecticide to control a number of pests such as termites, thrips, whiteflies, aphids and different beetles .

30. Panther - BB, a microbial insecticide, is of fungal origin causing a lethal disease (white muscadine disease) in insects. Wide variety of insects like white flies, aphids, mealy bugs, thrips, leaf hoppers etc. succumb to the application of Panther - BB. Panther BB does not leave any residual toxicity on the crops B eauvaria , Commercially…

31. W ide range of targets Aphids Whiteflies Meal y bugs Lygus bugs Chinch bug Beetles  Psyllids  Grasshoppers  Black vine weevil  Thrips  Strawberry root weevil  Termites  Coffee borer beetle  Fire ants  Colorado potato beetle  Flies  Mexican bean beetle  Stem Borers  Japanese beetle  Mites  Boll weevil  Fungal gnats  Cereal leaf beetle  Shoreflies  Bark beetles Caterpillars European corn borer Codling moth Douglas fir tussock moth Silkworm

32. E ntomogenous Species of Hirsutella SPECIES ON ORTHOPTERA [ Grasshoppers and locusts; crickets] Hirsutella fusiformis SPECIES ON HOMOPTERA [Plant lice (aphids); whiteflies; cicadas; leafhoppers; plant hoppers; scale insects and mealybugs; spittle insects] Hirsutella citriformis Hirsutella abeitina SPECIES Of COLEOPTERA [ Bee tles] Hirsutella entomophila

33. …Continued SPECIES ON LEPIDOPTERA [Moths and butterflies] Hirsutella barberi Hirsutella subulata Hirsutella gigantea SPECIES ON DIPTERA [true flies and mosquitoes and gnats and crane flies] Hirsutella radiata Hirsutella dipterigena SPECIES ON HYMENOPTERA [bees; wasps; ants; ichneumons; sawflies; gall wasps; etc.] Hirsutella saussurei Hirsutella formicarum

34. Crop disease Pathogen Biocontrol agents Blight of Sesamum Phytophthora sp. T. harzianum T. viride Root rot of Sesamum M. phaseolina Trichoderma sp. Gliocladium sp. Root rot chilli S. rolfsii T. harzianum Dieback of chilli Colletotrichum capsici T. viride T. harzianum Wilt of eggplant F. solani T. viride T. koningii Damping-off of eggplant P. aphanidermatum T. viride Table 16.1 List of crop diseases controlled by various biocontrol agents Table 16.1 List of crop diseases controlled by various biocontrol agents  

35. Wilt of tomato F. oxysporum T. harzianum f.sp. lycopersici Root knot of tomato Meloidogyne incognita T. harzianum M. javanica Wilt of okra Pythium spp. A. niger Leaf blight of sunflower Alternaria helianthi T. virens Wilt of pigeon pea Fusarium udum T. viride T. hamatum T. harzianum T. koningii Wilt of chickpea F. oxysporum T. viride f.sp. ciceri T. harzianum T. virens Dry root rot of soybean M. phaseolina T. viride T. harzianum Stem rot of groundnut Sclerotium rolfsii T. harzianum Damping-off of mustard Pythium aphanidermatum T. harzianum T. viride Root rot of mung bean M. phaseolina T. harzianum T. viride Table 16.1 List of crop diseases controlled by various biocontrol agents  

36. Advantages of BioControl Biological control provides an alternative to the use of synthetic pesticides with the advantages of greater public acceptance and reduced environmental impact Antagonism between species of naturally competing fungi has been observed Trichoderma species are free-living fungi which are highly interactive in root, soil and foliar environments. Considered to be eager colonizers and particularly invasive fungi, they work against fungal phytopathogens either indirectly by competing for nutrients and space, modifying environmental conditions or promoting plant growth and plant defensive mechanisms and antibiosis ; or directly through mechanisms such as mycoparasitism .served in virtually every fungal ecosystem

37. Advantages of Biological Control   Biological control is an eco-friendly approach, as it is nontoxic to plants and a non- targeted microbe, decreases the pesticide accumulation in food, regulates the activ - ity of natural predators, and increases the microbial diversity in managed system. This process is less prominent but more stable and long-lasting, in comparison to physical and chemical controls (Baker and Cook 1974 ). Some of the advantages of biological controls are listed below:

38. Biocontrol Agents Are Host Specific Nontoxic to Plants Application by Conventional Methods Ability to Multiply in Their Target Host Production Technology Available Advantages of Biological Control

39. High Cost of Production Additional Control Measures Time of Application Mortality Viability Difficulty in Mass Production Legal Protection Disadvantages of Biocontrol Agents

40. Conclusion   The extensive use of fertilizer and pesticides has resulted in environmental pollution (especially, soil pollution). Over-usage of these agrochemicals and rumors created by the pesticide rivals have significantly reformed the attitude of consumers to use pesticides in their agricultural land. Controlling the large proportion of pest and disease has elevated the usage of these hazardous chemicals for proper management. Generation of resistant against fungicide and pesticide is emerging as new problem. Thus, there is a need to employ eco-friendly pesticides as they are less toxic and have low residual problem and low level of resistance. Thus, biological control approach should be used in collaboration , as efficiency of one approach varies with time, location, and environmental conditions .

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