There are about 150 species worldwide (north temperate regions, tropical mountains, South America) of which five are native to southern Africa and 10 naturalised. 

Species native to southern Africa

List from Plants of Southern Africa - an Online Checklist (SANBI).

Bromus firmior
Bromus leptoclados
Bromus natalensis
Bromus pectinatus
Bromus speciosus

Species naturalised in southern Africa

List from Plants of Southern Africa - an Online Checklist (SANBI) and Flora of Zimbabwe.

Bromus alopecurus
Bromus catharticus
Bromus commutatus
Bromus diandrus
Bromus hordeaceus
Bromus inermis
Bromus madritensis
Bromus rigidus
Bromus rubens
Bromus tectorum