Taxonomic Review of the Genus Echinochloa in Korea (II): Inferred from Simple Sequence Repeats

Abstract

The genus Echinochloa (L.) P. Beauv. is a very difficult genus due to many interspecific and intraspecific forms found in the nature. This genus is still taxonomically controversial due to the absence of reliable morphological characters, resulting in poor taxonomic understanding of the genus. It has approximately 3040 species, mainly distributed in the tropical and warm temperate regions, usually associated with wet or damp places, of the world (Clayton and Renvoize, 1999). This genus includes some of noxious weeds, such as E. crusgalli (L.) P. Beauv., E. oryzicola Vasinger, and E. colona (L.) Link in agricultural areas of the world. The dominance of these species causes serious yield loss if they are not appropriately controlled in the fields (Hill et al., 1985). The two species, E. crus-galli and E. oryzicola are problematic weeds in Korean agricultural fields as well. The Korean agronomists are confused about identifying this difficult genus using morphological characters because E. crus-galli not only exhibits very diverse morphological and ecological types, but also includes several varieties such as var. echinata (Willd.) A. Chev. and var. praticola Ohwi. However, these two varieties, echinata and praticola, have been treated as synonyms of var. crus-galli depending on taxonomists (The Plant List, 2014). It has been known that eight morphological taxa of the genus, E. crus-galli var. crus-galli, var. echinata, var. praticola, E. oryzicola, E. colona, E. glabrescens Munro ex Hook.f., E. oryzoides (Ard.) Fritsch, and E. esculenta (A.Braun) H.Scholz, are distributed throughout Korea (Lee et al., 2013). Echinochloa crus-galli grows in the upland fields and also in paddy fields whereas E. oryzicola is frequently found in paddy fields. These two species are mainly found in the whole country. Existence of E. colona and E. glabrescens in Korea, however, should be reexamined. The result of a previous study showed that two species E. colona and E. glabrescens collected from Korea was clustered with E. crus-galli. They were not clustered with E. colona collected from China and/or formed independent clade (in press). The continuous use of the herbicides which have the same ABSTRACT. Echinochloa (L.) P. Beauv. includes some of the noxious weeds, causing a serious yield loss when they are dominant in the fields. Identification of the Echinochloa is very difficult because many interspecific and intraspecific forms of the species are found. However, it is important to identify the species exactly and to know the genetic diversity of the species for effective weed management. This study was conducted to identify and summarize the Echinochloa species by comparing the genetic variation and relationship among Korean Echinochloa species using SSR. The genetic diversity of 107 individuals, including seven species were assessed using five SSR markers. UPGMA dendrogram generated two clades (I and II) and clade II divided again into two subclades (II-1 and II-2) whereas the model based genetic structure proposed four subpopulations. The two subpopulations were corresponded to clades I and II-1 and the other two were arranged to clade II-2 of the UPGMA dendrogram. We have concluded that E. colona and E. glabrescens might have not distributed in Korea. The biological varieties, praticola and echinata, of E. crus-galli should be treated as E. crus-galli. Korean Echinochloa should be summarized with four species, i.e., E. oryzicola, E. crus-galli, E. esculenta, and E. oryzoides.