Question

Which one is not a biofertiliser?

• A. $Rhizobium$
• B. $Agrobacterium$
• C. Mycorrhiza
  
• D. $Nostoc$

Answer 1

The correct option is B $Agrobacterium$

Introduction of biofertilisers
Biofertilisers include the fertilisers of biological origin including microorganisms that enrich the nutrient content of the soil and increase plant growth. The sources include:

• Cyanobacteria (like $Nostoc,Anabaena$)
• Free living nitrogen fixing bacteria ($Azotobacter,Azospirillum$)
• Symbiotic nitrogen fixing bacteria like Rhizobium

Mycorrhiza is a symbiotic association between fungi and the roots of higher plants which helps in phosphate solubilisation and its uptake by the plant helping in its enhanced growth.

$Agrobacterium$ as a pathogen
$Agrobacterium$ is a soil bacterium that infects plant cells causing crown gall disease. It has the ability to transfer a piece of DNA from Ti plasmid to the host genome. Hence, it is modified and used as a vector for introducing foreign DNA into the plants.

Final answer
(C) $Agrobacterium$