What is the name of the groove that is deeper and wider in B-DNA?

The groove that is deeper and wider in B-DNA is the major groove.

The two sugar-phosphate backbones of DNA are not positioned directly opposite one another, so the double helix has two unequal channels. The larger channel is the major groove, while the narrower channel is the minor groove. In standard B-DNA, the major groove is approximately 22 angstroms wide and 8.5 angstroms deep; the minor groove is about 12 angstroms wide and 7.5 angstroms deep.

The major groove exposes more information from the edges of the base pairs. That makes it a common recognition site for DNA-binding proteins, including many transcription factors. Proteins can read chemical patterns in the groove without opening the entire helix.

The minor groove also matters and is targeted by some proteins and small molecules. A frequent misconception is that “major” means biologically more important in every situation. The names primarily describe relative size. Groove dimensions can also change with DNA conformation: A-DNA and Z-DNA have different shapes and groove arrangements from B-DNA.