What is "tristachyideae"

Tristachyideae is a tribe of the Panicoideae subfamily in the grasses ( Poaceae), native to tropical and subtropical regions of Africa, Asia, and South America. There are around 70 species in eight genera. The tribe belongs to a basal lineage within the subfamily, and its genera were previously placed in tribes Arundinelleae or Paniceae, subfamily Arundinoideae, or the now-obsolete subfamily Centothecoideae. Species in this tribe use the C photosynthetic pathway.