Question

Which of the following can be used as a biocontrol agent in the treatment of plant disease
A. Trichoderma
B. Chlorella
C. Anabaena
D. Lactobacillus

Answer 1

Hint: Bio-control agents utilize the phenomena of natural antagonism like parasitism, predation and other similar mechanisms for the process of controlling pests in plants. They control harmful pests such as weeds, parasitic nematodes and other pests.

Complete answer: Trichoderma species belong to the fungal class Ascomycetes, they can be seen present abundantly in soil. They protect the roots of the plants by preventing pathogenic infestations. It is commonly used against infection-causing parasites in pulses, cotton, and onion. Various species of Trichoderma produce various volatile as well as non-volatile antibiotic enzymes which act antagonistically against parasitic organisms such as other fungi and nematodes.
Considering other options:
-Chlorella: It is a single-celled green alga, which is predominantly aquatic. It belongs to the division Chlorophyta. Benefits of the organism include functioning as a source of antioxidants, helping in cholesterol reduction, as well as being a source of proteins and carbohydrates.
-Anabaena: It is a cyanobacterium, which is filamentous and exists as plankton. They are found to have symbiotic relationships with certain plant species, functioning as a nitrogen fixer.
-Lactobacillus: It is a bacterial species found in the animal GI tracts. They produce lactic acid which has a protective function in the gut. They can be taken orally as medicine to restore the normal useful gut flora. They can be used commercially for the curdling of milk.
In the above-given options, all the organisms are found to have a symbiotic relationship with certain other organisms. But the one functioning as a biocontrol agent is the Trichoderma species in the treatment of plant diseases.
Hence, the most appropriate option is A.

Note: Other kinds of biological pest control agents include, insects such as spiders, beetles and dragonflies. Other kinds include bacteria belonging to the coccobacillus group. Various viruses can also function as biocontrol agents.