Plastome phylogenomics of sugarcane and relatives confirms the segregation of the genus Tripidium (Poaceae: Andropogoneae)

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 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.str. (Old World) and Erianthus s.str. (= 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.str. 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.