Test: Biogas, Biocontrol Agents & Biofertilisers: Microbes - NEET MCQ

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.

The Khadi and Village Industries Commission (KVIC) and the Indian Agricultural Research Institute (IARI) have played significant roles in the development of biogas technology in India. The Indian Council of Medical Research (ICMR) is unrelated to this field. Hence, the correct pair is A and C.

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.

(i) Lady bird – (C) Aphids
(ii) Mycorrhiza – (D) Glomus
(iii) Biological control – (B) Trichoderma
(iv) Biogas – (A) Methanobacterium

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.