What is the scientific name for the bacterium used to genetically engineer plants?

The bacterium used to genetically engineer plants is Agrobacterium tumefaciens.

This soil-dwelling, Gram-negative bacterium naturally transfers part of its DNA into plant cells. It causes crown gall disease by using a tumour-inducing, or Ti, plasmid. A segment called T-DNA enters the plant cell and can become integrated into the plant genome, altering cell growth and metabolism.

Scientists adapted this natural gene-transfer system for biotechnology by removing the tumor-causing genes and inserting a desired gene instead. These “disarmed” bacterial strains deliver engineered T-DNA into plant cells, where the cells can be selected and regenerated into whole plants. The method has been especially important for producing transgenic crops and laboratory plants.

The species is also known by the newer name Rhizobium radiobacter in some taxonomic treatments, but Agrobacterium tumefaciens remains the standard and canonical quiz answer. The other options are important bacteria, but they are not the classic natural gene-transfer tool used for plant transformation.