Study system
Paspalum vaginatum is distributed throughout tropical and
subtropical saline ecosystems worldwide (Duncan & Carrow, 2000). It is
characterized by two common ecotypes that differ in shoot and leaf
morphology, referred to as the ‘coarse-textured’ and ‘fine-textured’
ecotypes (Fig. 1B; Duncan & Carrow, 2000). The fine-textured ecotype is
more economically important because its prostrate growth form and
smaller leaves makes it valuable for use as a turfgrass; the
coarse-textured ecotype has also seen limited use as a dune stabilizer.
Within the US, the coarse-textured ecotype is typically found on the
Gulf Coast and Florida, while fine-textured plants are found on the
Atlantic coast from North Carolina to Georgia (Duncan & Carrow, 2000).
Due to the focus on collecting samples for turf breeding programs, the
USDA P. vaginatum germplasm collection is composed almost
entirely of fine-textured accessions (USDA-ARS, 2015).
Paspalum vaginatum and its closely related non-halophytic sister
species P. distichum together comprise the Disticha clade, which
is distantly related to the other ca. 300 species in the genus (Burson,
1981; Scataglini, Zuloaga, Giussani, Denham, & Morrone, 2014). The two
species are morphologically very similar and often confused (Bor &
Guest, 1968; Brummitt, 1983), although they are distinguishable based on
cpDNA and nuclear sequences (Scataglini, Zuloaga, Giussani, Denham, &
Morrone, 2014). Unlike P. vaginatum , P. distichum is
believed to be predominantly hexaploid (2n = 60), with tetraploid (2n =
40), pentaploid (2n = 50) and hyperpentaploid (2n = 52, 54, 57, and 58)
cytotypes occurring occasionally in the wild Echarte, Clausen, & Sala,
1992). A putative diploid P. distichum accession has also been
reported (Eudy, Bahri, Harrison, Raymer, & Devos, 2017).