Nuclear GPA1 and Chloroplast DNA Sequences Reveal a Natural Hybrid Between Leersia sayanuka and Leersia oryzoides in J apan

The large type (LT) of Leersia has recently been recognized as a perennial weed inhabiting paddy levees in Japan. Although the LT has been treated as L. sayanuka owing to confusion in plant identification, it differs from L. sayanuka in both morphological and ecological characteristics. To clarify the genetic relationships between the LT and other Japanese Leersia species, including L. sayanuka , we determined chromosome numbers and performed phylogenetic analyses using sequences of the partial nuclear GPA1 gene and four chloroplast genome regions. The chromosome counts, phylogenetic analysis of partial GPA1 sequences, and observed sterility together suggest that the two LT accessions examined in this study are tetraploid (2 n = 48) plants of hybrid origin, most likely F 1 hybrids between tetraploid lineages of L. sayanuka (2 n = 48) and L. oryzoides (2 n = 48). The phylogenetic analysis of chloroplast DNA sequences supported this inferred hybrid origin, with LT haplotypes clustering closely with those of either L. sayanuka or L. oryzoides . Our findings provide novel insights into the origin of LT and suggest that it is unlikely to represent intraspecific variation within L. sayanuka .