Microbes as Biocontrol Agents Questions in English

(B) Cyclosporin $A$ is an immunosuppressive agent produced by the fungus $Trichoderma$ $polysporum$.
In the context of biological control,$Trichoderma$ species are free-living fungi that are very common in the root ecosystems.
They are effective biocontrol agents against several plant pathogens,specifically soil-borne pathogenic fungi.
Therefore,they are used to control pathogenic fungi.

(B) The correct answer is $B$.
$Thuriocide$ is a commercial preparation of $Bacillus$ $thuringiensis$ $(Bt)$,which is a well-known microbial insecticide.
It contains the $Bt$ toxin (cry protein) that is toxic to specific insect larvae.
$Rotenone$ is a plant-derived insecticide,while $Baygon$ and $Temik$ are synthetic chemical insecticides.

(B) The bacterium $Bacillus$ $thuringiensis$ $(Bt)$ is widely used as a bio-insecticide.
It produces a specific insecticidal protein (Cry protein) that is toxic to certain insect larvae,such as lepidopterans,coleopterans,and dipterans.
When these larvae ingest the spores or crystals of the bacterium,the toxin is activated in their alkaline gut,leading to their death.
This makes it an effective biological control agent for crop protection.

(D) $Bacillus \text{ } thuringiensis$ is a biological insecticide.
It produces specific proteins (Cry proteins) that kill the larvae of various types of insects.
It is used for the control of pests such as moths,flies,and mosquitoes.
Therefore,the correct answer is 'All of the above'.

(C) The sterile insect technique $(SIT)$ is a method of biological control where large numbers of sterile insects are released into the environment. These sterile insects mate with wild populations,resulting in no offspring,which leads to a decline in the population over time. The screwworm fly ($Cochliomyia$ $hominivorax$) was the first insect successfully controlled using this technique.

(A) Gambusia is a type of larvivorous fish that feeds on mosquito larvae. By introducing Gambusia into stagnant water bodies,the population of mosquito larvae is significantly reduced,which helps in the biological control of mosquitoes and prevents diseases like malaria and dengue.

(B) Gambusia is a genus of fish,commonly known as mosquito fish. It is used as a biological control agent to control mosquito larvae in water bodies,thereby helping to prevent diseases like malaria and dengue.

(B) $Gambusia$ is a larvivorous fish. When introduced into ponds or stagnant water bodies,it feeds on the larvae of mosquitoes. By consuming these larvae,it effectively prevents the breeding of mosquitoes,thereby acting as a biological control agent for mosquito-borne diseases like malaria and dengue.

(C) The fish $Gambusia$ is a larvivorous fish. It is introduced into ponds and water bodies to feed on mosquito larvae,thereby acting as a biological control agent to prevent the spread of diseases like malaria and dengue.

(D) The fish $Gambusia$ is a larvivorous fish. It is widely used in biological control programs to manage mosquito populations. By feeding on the larvae of mosquitoes in stagnant water bodies,it effectively reduces the transmission of vector-borne diseases such as malaria and filariasis.

(C) Baculoviruses are pathogens that attack insects and other arthropods.
These are mostly in the genus $Nucleopolyhedrovirus$.
These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications.
They have been shown to have no negative impacts on plants,mammals,birds,fish,or even non-target insects,which is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management $(IPM)$ program.

(B) Bionematicides are biological agents used to control plant-parasitic nematodes.
They are derived from microorganisms such as bacteria (e.g.,$Pasteuria \ penetrans$) or fungi (e.g.,$Paecilomyces \ lilacinus$) that infect or kill nematodes,thereby protecting crops from damage caused by these soil-borne pests.

(A) Chemical pesticides are toxic and harmful to the environment,causing pollution and affecting non-target beneficial organisms.
Biocontrol agents (like $Bacillus$ $thuringiensis$,$Trichoderma$,and $Baculoviruses$) are specific to pests and do not harm beneficial insects or the environment.
Therefore,the use of biocontrol agents is necessary to replace harmful chemical pesticides.
Biological control agents help maintain the ecological balance by controlling pest populations without disrupting the food chain or causing environmental toxicity.
Thus,both $A$ and $R$ are true,and $R$ is the correct explanation of $A$.

(C) The microorganism used to control pests harmful to cotton is the bacterium $Bacillus$ $thuringiensis$ $(Bt)$.
This bacterium produces specific insecticidal proteins (Cry proteins) that are toxic to certain insect larvae,such as the cotton bollworm.
When these larvae ingest the toxin,it gets activated in their alkaline gut,leading to their death.
Therefore,the correct option is $C$.

(D) Bionematicides are biological agents used to control plant-parasitic nematodes. These agents include various microorganisms such as specific bacteria (e.g.,$Pasteuria \ penetrans$),fungi (e.g.,$Paecilomyces \ lilacinus$,$Arthrobotrys \ oligospora$),and sometimes viruses that infect nematodes. Since all these groups of microorganisms are utilized in the development of bionematicides,the correct answer is $D$.

(C) Baculoviruses are pathogens that attack insects and other arthropods.
These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications.
They have been shown to have no negative impacts on plants,mammals,birds,fish,or even on non-target insects.
This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management $(IPM)$ programme.

(D) $Trichoderma$ species are free-living fungi that are very common in root ecosystems.
They act as effective biocontrol agents for several plant pathogens.
Since they do not depend on a host for survival and exist independently in the soil,they are classified as free-living organisms.

(C) The use of biological methods for controlling plant diseases and pests is known as $Biological$ $control$ or $Biocontrol$. This method relies on natural predation, parasitism, or other natural mechanisms rather than the use of synthetic chemicals. For example, the use of $Bacillus$ $thuringiensis$ $(Bt)$ bacteria to control butterfly caterpillars is a classic example of biological control.

(C) The fungus $Trichoderma$ is a free-living fungus that is very common in the root ecosystems. It is an effective biocontrol agent for several plant pathogens,particularly those affecting cereal crops and vegetables. It acts by parasitizing the pathogens and producing antifungal compounds.

(B) Biocontrol agents are organisms that are used to control plant diseases and pests.
$1$. $Pseudomonas$ species are used to control root-borne pathogens.
$2$. $Baculoviruses$ (specifically $Nucleopolyhedrovirus$) are excellent narrow-spectrum insecticidal agents.
$3$. $Trichoderma$ is a fungus that is very effective against several plant pathogens.
Therefore,the group consisting of biocontrol microorganisms is $Pseudomonas$,$Baculovirus$,and $Trichoderma$.

(A) The genus $Trichoderma$ consists of free-living fungi that are very common in root ecosystems. These fungi are effective biocontrol agents of several plant pathogens. They act as antagonists by competing for space and nutrients,producing antibiotics,and parasitizing the pathogens. Therefore,$Trichoderma$ species are widely used in the biological control of plant diseases.

(B) The use of biological control agents to manage plant diseases is a sustainable agricultural practice.
Specifically,certain biological agents are used to control nematodes that infect the roots of various crops like vegetables,fruits,and cereals.
These agents are collectively referred to as $Bionematicides$.
For example,the fungus $Paecilomyces$ $lilacinus$ is a well-known $Bionematicide$ used to control root-knot nematodes.

(B) Bionematicides are biological control agents used to manage populations of nematodes. Nematodes are microscopic roundworms that often infest the roots of plants,causing significant agricultural damage. By using specific microorganisms or their derivatives,farmers can control these pests without relying on harmful chemical pesticides.

(A) The bacterium $Bacillus \ thuringiensis$ (often abbreviated as $Bt$) is widely used as a biological control agent.
It produces a specific insecticidal protein (Cry protein) that is toxic to certain insect larvae,such as those of butterflies and moths,which are common pests in fruit trees and crops.
When these larvae ingest the bacterial spores,the toxin is activated in their gut,leading to their death while remaining harmless to other organisms.

(B) In agriculture,organisms such as insects,rodents,weeds,and pathogens that cause damage to crops are collectively referred to as $Pests$. $Insecticides$ are chemicals used to kill insects,$Antibiotics$ are used to treat bacterial infections,and $Fertilizers$ are substances added to soil to provide nutrients for plant growth. Therefore,the correct term for harmful components is $Pests$.

(A) The microorganism $Bacillus$ $thuringiensis$ (often abbreviated as $Bt$) is used as a biological control agent to manage harmful pests in crops like cotton and fruit trees.
It produces a specific insecticidal protein (crystal protein) that kills the larvae of certain insects when ingested.
This makes it an effective bio-pesticide, reducing the need for chemical pesticides.

(C) The biological control agent used for the treatment of diseases in cereal crops and vegetables is $Pseudomonas$ species.
$Pseudomonas$ bacteria are known for their ability to colonize the rhizosphere and suppress various soil-borne plant pathogens.
$Bacillus \text{ } thuringiensis$ is primarily used as a bio-insecticide.
Nematodes are often used as biological control agents against specific insect pests.
Baculoviruses are pathogens that attack insects and other arthropods, making them effective bio-insecticides.

(D) Mycoherbicides,also known as fungal herbicides,are biological control agents used to manage weeds.
These are derived from specific species of fungi that act as pathogens to target weeds without harming the crop plants.
For example,the fungus $Phytophthora$ $palmivora$ is used as a mycoherbicide to control milkweed vines in citrus orchards.
Therefore,the correct answer is $D$.

(B) Biological control refers to the use of biological methods for controlling plant diseases and pests. Biological control agents (like $Bacillus \text{ } thuringiensis$) are used to kill or control pests, which protects crops. Thus, Assertion $(S)$ is true.
Crop production is significantly reduced by the infestation of pests, which damage plants and reduce yield. Thus, Reason $(R)$ is true.
However, the reason why biological control agents are used is to protect crops from the damage caused by pests. The fact that pests reduce crop production is the reason why we need biological control, but it does not explain the mechanism of how biological control agents destroy pests. Therefore, $R$ is not the correct explanation of $S$.

(A) $Bacillus$ $thuringiensis$ (often abbreviated as $Bt$) is a soil-dwelling bacterium that produces insecticidal crystal proteins (Cry proteins) during sporulation.
These proteins are toxic to specific insect larvae,such as those of lepidopterans,coleopterans,and dipterans.
Because of this property,$Bt$ spores and their toxins are formulated into commercial products and used as biological control agents or bio-insecticides to protect crops from pests without harming beneficial insects or the environment.
Therefore,it is widely used as a bio-insecticide.

(B) The bacterium $Bacillus \text{ } thuringiensis$ (often referred to as $Bt$) is widely used as a biological control agent.
It produces a specific insecticidal protein (Cry protein) that is toxic to certain insect larvae.
When these larvae ingest the bacterial spores, the toxin is activated in their gut, leading to their death.
This bacterium is specifically used to protect crops like cotton $(Bt \text{ } cotton)$ and various fruit trees from harmful pests.

(D) Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus $Nucleopolyhedrovirus$. These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications. They have been shown to have no negative impacts on plants,mammals,birds,fish,or even non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management $(IPM)$ programme.

(A) Bionematicides are biological agents used to control plant-parasitic nematodes. Nematodes are microscopic roundworms that often live in the soil and damage plant roots,leading to reduced crop yields. Examples of bionematicides include certain species of fungi (like $Paecilomyces$ $lilacinus$) and bacteria that infect or parasitize these nematodes,thereby reducing their population in the soil.

(D) The bio-pesticide 'Quantum-$4000$' is derived from the fungus $Trichoderma$ $harzianum$ (or other $Trichoderma$ species).
$Trichoderma$ species are free-living fungi that are very common in the root ecosystem.
They act as effective biocontrol agents against several plant pathogens,especially those affecting cereal crops and vegetables.
Therefore,the correct option is $D$.

(A) The fungus $Trichoderma$ species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens. $Pseudomonas$ is a bacterium,not a fungus. $Aspergillus$ and $Penicillium$ are fungi but are not primarily used as biocontrol agents in the same context as $Trichoderma$.

(B) Bio-pesticides are defined as biological agents,such as living organisms (bacteria,fungi,viruses) or their natural products,that are used to control pests,weeds,and diseases in crops. Unlike synthetic chemical pesticides,they are generally more specific in their action and environmentally friendly. For example,the bacterium $Bacillus$ $thuringiensis$ $(Bt)$ is a well-known bio-pesticide.

(D) The correct answer is $Trichoderma$.
$Trichoderma$ species are free-living fungi that are very common in the root ecosystems.
They are effective biocontrol agents of several plant pathogens.
$Bacillus$ $thuringiensis$ is used to control butterfly caterpillars,$Baculoviruses$ are used as narrow-spectrum insecticidal applications,and $Glomus$ is a genus of arbuscular mycorrhizal fungi.

(A) Biocontrol agents are living organisms used to control pests in agriculture. Unlike chemical pesticides,which are often toxic and cause environmental pollution,biocontrol agents are self-replicating and target-specific. They do not leave harmful residues in the environment,making them an eco-friendly alternative. Therefore,they are considered self-replicating in the context of their ability to multiply and persist in the environment to manage pest populations.

(D) $1$. $Trichoderma$ is a free-living fungus used as a biocontrol agent against several plant pathogens.
$2$. $Rhizobium$ is a symbiotic bacterium that fixes atmospheric nitrogen in the root nodules of leguminous plants.
$3$. $Azotobacter$ is a free-living bacterium that fixes atmospheric nitrogen in the soil.
$4$. $Glomus$ is a genus of arbuscular mycorrhizal fungi $(AMF)$. These fungi form a symbiotic association with plant roots (mycorrhiza) to help in phosphorus absorption, not nitrogen fixation. Therefore, the pair $Glomus - \text{Symbiotic } N_2\text{-fixer}$ is incorrect.

(D) Microbial biocontrol agents are used in agriculture to reduce the reliance on toxic chemical pesticides and insecticides.
$1$. They are specific in their action and do not harm non-target organisms,which helps in maintaining the balance of the ecosystem.
$2$. Unlike chemical pesticides,they do not leave toxic residues in the soil,water,or air,thereby preventing environmental pollution.
$3$. Therefore,they are considered an environmentally friendly and sustainable approach to pest management.
Since both options $B$ and $C$ are correct,the most appropriate answer is $D$.

(A) The correct matches are as follows:
$(a)$ $B.T.$ bacteria (Bacillus thuringiensis) is used for controlling crop-sucking pests in crops like $(r)$ Cotton $(iii)$.
$(b)$ Trichoderma is a $(p)$ free-living fungus used for $(v)$ crop disease control.
$(c)$ Baculovirus is a $(u)$ biological control agent used against $(i)$ arthropods.
$(d)$ Pseudomonas (specifically certain strains like Quantum-$4000$) acts as a $(t)$ bionematicide against $(ii)$ cereal crops (or specifically against nematodes).
Thus,the correct sequence is $a-r-iii, b-p-v, c-u-i, d-t-ii$.

(B) The fungus $Trichoderma$ is a free-living fungus that is very common in the root ecosystems.
It is an effective biocontrol agent for several plant pathogens.
$Aspergillus$ $niger$ is used for the production of citric acid.
$Penicillium$ $notatum$ is used for the production of penicillin.
$Monascus$ $purpureus$ is used for the production of statins.
Therefore,the correct option is $B$.

(C) Baculoviruses are pathogens that attack insects and other arthropods. They are excellent candidates for species-specific,narrow-spectrum insecticidal applications. They have been shown to have no negative impacts on plants,mammals,birds,fish,or even on non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management $(IPM)$ program.

(A) The biological control of pests and diseases in crops is an important aspect of modern agriculture. Quantum-$40$ is a well-known biological preparation used as an effective agent for managing various diseases in cereal crops and vegetables. It acts as a bio-pesticide/bio-fungicide,helping to protect plants from pathogenic infections.

(D) The bio-insecticide 'Quantum-$4000$' is derived from the bacterium $Pseudomonas$ $fluorescens$.
$Pseudomonas$ species are widely used in agriculture as biological control agents because they produce various secondary metabolites that inhibit the growth of plant pathogens and pests.
Therefore,the correct option is $D$.

(D) $IPM$ stands for Integrated Pest Management.
It is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control,habitat manipulation,modification of cultural practices,and use of resistant varieties.
This approach minimizes the use of chemical pesticides,thereby reducing risks to human health and the environment.

(A) The fungus $Trichoderma$ species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens. $Bacillus$ $thuringiensis$ is a bacterium,not a fungus. $Pseudomonas$ is also a genus of bacteria. $Yeast$ is a fungus but is used in fermentation,not as a biocontrol agent for crop diseases. Therefore,the correct answer is $Trichoderma$.

(B) Fungicides are chemical compounds or biological organisms used to kill or inhibit the growth of fungi and their spores. They are specifically designed to control fungal diseases in plants and crops. Therefore,the correct term for substances that kill fungi is $Fungicides$.

(A) Malaria is a disease caused by the protozoan parasite $Plasmodium$.
Mosquitoes act as vectors for this disease.
$Gambusia$ is a larvivorous fish that feeds on the larvae of mosquitoes.
By introducing $Gambusia$ into water bodies (like ponds and ditches),the population of mosquito larvae is significantly reduced,which in turn helps in the biological control of malaria.

(B) : Biopesticides are biological agents used for the control of weeds, insects, and pathogens. The microorganisms used as biopesticides include viruses, bacteria, protozoa, fungi, and mites. Some of these are used on a commercial scale. The most important example is the soil bacterium, $Bacillus \text{ } thuringiensis$ $(Bt)$. Spores of this bacterium produce an insecticidal $Cry$ protein. When ingested by butterfly caterpillars, these spores release the toxin, which kills the larvae.