The origin and evolution of Eragrostis tef (Poaceae) and related polyploids: evidence from nuclear waxy and plastid rps16

Abstract

Tef (Eragrostis tef; Poaceae) is an allotetraploid (2n = 4x = 40) cereal crop whose origin within the large genus Eragrostis is unknown. Previous studies have suggested a total of 14 wild Eragrostis species as potential progenitors. Phylogenetic analysis of sequence data from the nuclear gene waxy and the plastid locus rps16 strongly supports the widely held hypothesis of a close relationship between tef and E. pilosa, a wild allotetraploid. Eragrostis heteromera, another previously proposed progenitor, is shown by the waxy data to be a close relative of one of the tef genomes. Other putative progenitors included in the taxon sample are not supported as closely related to tef. Plastid sequences from five varieties of tef and four E. pilosa accessions are identical and therefore are uninformative with respect to the question of multiple origins of these polyploids. The waxy phylogeny also resolves the relationships among other allopolyploids, supporting a close relationship between the morphologically similar allotetraploids E. macilenta, E. minor, and E. mexicana. Eragrostis cilianensis, another morphologically similar allopolyploid, appears to have shared one diploid progenitor with these species but derived its other genome from an unrelated diploid.

A Preliminary Phylogenetic Analysis of the Grass Subfamily Pooideae (Poaceae), with Attention to Structural Features of the Plastid and Nuclear Genomes, Including an Intron Loss in GBSSI

“…in the nuclearencoded gene granule-bound starch synthase (GBSSI, or waxy). Variation patterns in GBSSI have proven useful in analyses at a range of taxonomic levels within the grasses, from the overall phylogenetic structure of the family to that among closely related species, including the details of polyploidization events (e.g., Mason-Gamer et al 1998;GPWG 2001;Mason-Gamer 2001;Mathews et al 2002;Ingram and Doyle 2003). In the present work we report a phylogenetically informative loss of GBSSI intron 10 within Poeae s.l.…”

Eragrostis (Poaceae): Monophyly and Infrageneric Classification

“…These groups are far from uniform in many of the characters used in the phylogenetic analysis, which necessitates coding a number of polymorphisms in the matrix. In addition, the monophyly of these two subgenera has not been confirmed by phylogenetic analyses of independent data sets (Ingram and Doyle 2003). Both of these factors could have seriously affected the outcome of the phylogenetic analysis of the subfamily.…”

“…PCR amplification, sequencing, and sequence alignment of waxy and rps16 were performed as described in Ingram and Doyle (2003). Some of the sequences used in this study were previously published (Ingram and Doyle 2003: GenBank accessions AY136828-AY136942); new sequences were deposited in GenBank (accession numbers AY508649-AY508691, AY509525, and AY509526). All sequences were aligned with ClustalX (Thompson et al 1997) using a variety of gap opening and extension penalties to test for the sensitivity of the phylogenetic analyses to different alignments.…”

A classification of the Chloridoideae (Poaceae) based on multi-gene phylogenetic trees

“…were found embedded within a polyphyletic Eragrostis . Based on a survey of rps16 and nuclear waxy gene sequences from a broad range of Eragrostis species, Ingram and Doyle (2003, 2004, 2007 have advocated that other small segregate genera such as Acamptoclados Nash, Diandrochloa De Winter, and Neeragrostis Bush be included with Eragrostis. Roodt-Wilding and Spies (2006) in their ITS and trnL-F strict consensus tree found Catalepis, Cladoraphis, and Pogonarthria all embedded in a polyphyletic Eragrostis clade.…”