Q.Assertion : Agrobacterium tumifaciens is popular in genetic engineering because this bacterium is associated with the root nodules of all cereals and pulse crops
Reason: A gene incorporated in the bacterial chromosomal genome gets atomatically transferred to the cross with which bacterium is associated.

Step 1. Test the Assertion. The chapter identifies Agrobacterium tumefaciens as the bacterium responsible for inducing tumours (crown gall) in dicot plants, and as popular in genetic engineering precisely because of this natural gene-transfer ability via its Ti plasmid - not because it is 'associated with the root nodules of all cereals and pulse crops'. Root-nodule association with pulse (legume) crops is instead a well-known feature of an entirely different bacterium, Rhizobium, and cereals are not nodulated by any bacterium in this way at all. The Assertion is false.

Step 2. Test the Reason. The chapter is explicit that what actually transfers into the plant genome is the T-DNA segment of the Ti plasmid, not a gene from the bacterial chromosomal genome, and this transfer happens at a wound site on infection - not 'automatically... to the cross with which bacterium is associated'. The Reason misdescribes both the mechanism (plasmid T-DNA, not chromosomal DNA) and the trigger (infection at a wound, not simple bacterial 'association'). The Reason is also false. …

Check the Assertion and the Reason separately against the chapter's actual description of Agrobacterium tumefacie …

• Confusing Agrobacterium's tumour-inducing role with Rhizobium's genuinely nodule-forming, nitrogen-fixing role in legumes. …