Sugarcane (Saccharum officinarum) is one of the most important crops in
the world and a major source of sugar for human consumption. Despite this immense
value, the circumscription of the genus Saccharum is complex, contentious, and largely
unresolved. Saccharum is either accepted in a broad sense by some authors or split into
various genera such as Erianthus and Tripidium by others. A plastome phylogenomic
analysis of sugarcane and relatives was performed in order to investigate generic
delimitation, with emphasis on Tripidium (= Erianthus sect. Ripidium). Our plastome
analysis demonstrates that Saccharum s.l. is polyphyletic and Tripidium (distributed in
the Old World) belongs to a distinct lineage from Saccharum s.s. (Old World) and
Erianthus s.s. (= Erianthus sect. Erianthus, New World). Therefore, this study confirms
the recognition of Tripidium as a genus distinct from Saccharum and Erianthus, which
is also supported by morphology and nuclear markers. The circumscription of Erianthus
s.s. remains unclear since our results are consistent with either considering it as a
distinct genus or including it in Saccharum. Better understanding of the evolutionary
relationships of sugarcane and relatives may be useful for the selection of potential taxa
for interspecific and intergeneric crosses in the genetic improvement of sugarcane. A
taxonomic treatment of the six species of Tripidium is also presented, including
descriptions, illustrations, data on geographical distribution, and three new
nomenclatural combinations. Less...