Biogas, Biocontrol Agents & Biofertilisers: Microbes - Free MCQ Practice

Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica.

Thus gobar (excreta/dung) of cattle is rich in these bacteria. Dung can be used for generation of biogas, commonly called gobar gas.
The residue left after methane production from cattle dung is used as manure.

Endomycorrhizal fungi (more commonly referred to as endomycorrhizae) is one of the major types of known mycorrhizae which differs from the another type of mycorrhizae, ectomycorrhizae, in structure. Unlike ectomycorrhizae which form a system of hyphae that grow around the cells of the root, the hyphae of the endomycorrhizae not only grow inside the root of the plant but penetrate the root cell walls and become enclosed in the cell membrane as well. This makes for a more invasive symbiotic relationship between the fungi and the plant. The penetrating hyphae create a greater contact surface area between the hyphae of the fungi and the plant.
Glomus is a genus of endomycorrhizal fungi, and all species form symbiotic relationships (mycorrhizas) with plant roots. 

A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma.

Correct Answer: A - KVIC and IARI.

KVIC played a key role in promoting and implementing small-scale and household biogas plants across rural India, supporting dissemination and practical adoption.

IARI (Indian Agricultural Research Institute) carried out research and development related to agricultural waste management and improvements in digester designs and anaerobic processes suitable for Indian conditions.

ICMR is concerned with medical research and is not responsible for biogas technology; ICAR is the agricultural research council, while IARI is a research institute under that system. Hence the pair KVIC and IARI is the correct combination.

Nostoc, Anabaena, and Oscillatoria are cyanobacteria capable of nitrogen fixation. Yeast is a fungus and cannot fix nitrogen. Thus, A, B, and C are correct.

Correct option: B

• i → C: A ladybird is a predator of sap-sucking insects; it commonly feeds on aphids, so it matches C.

• ii → D: Mycorrhiza refers to symbiotic fungi associated with plant roots; Glomus is a genus of arbuscular mycorrhizal fungi, so it matches D.

• iii → B: Biological control uses living organisms to control pests and pathogens; the fungus Trichoderma is used as a biocontrol agent against plant diseases, so it matches B.

• iv → A: Biogas production involves methanogenic archaea; genera such as Methanobacterium are methanogens involved in methane formation, so it matches A.

Therefore option B is the correct choice (i-C, ii-D, iii-B, iv-A).

Biocontrol agents are organisms used to control pests or pathogens biologically.
Trichoderma is a fungus used against plant pathogens.
Baculovirus (like Nucleopolyhedrovirus) is used to target insect pests.
Bacillus thuringiensis is a bacterium producing toxins effective against insects.
Hence, Option C correctly lists known biocontrol agents.

Baculoviruses are viral pathogens that specifically infect arthropods, especially insects, and are effectively used as biological control agents.
Trichoderma is a fungus used against plant pathogens, not arthropods.
Agrobacterium tumefaciens causes plant diseases.
E. coli is a gut bacterium and not used for insect biocontrol.