Echinochloa oryzicola (Vasinger) Vasinger (E As.) – A very rare and ephemeral alien. Several plants were found on the unloading quay of a mill at the Amerikadok in the Antwerp port area in 2016. The plants were associated with other rice field weeds such as Ammannia coccinea, Diplachne fusca subsp. fascicularis, Leersia oryzoides, Paspalum distichum, etc. In the same year also seen on rough ground in Genk, without obvious introduction vector.
Echinochloa oryzicola is readily distinguished from the other species of the genus found so far in Belgium by the large, unawned spikelets (ca. 5 mm long) and caryopses (ca. 2-3 mm long), the strictly erect inflorescence and the pure green color of the entire plant. Vegetatively, it is much reminiscent of rice and it is an obligate weed of rice fields.
This species is commonly naturalized in rice fields in southern Europe (Costea & Tardiff 2002) and is very variable. European plants usually have a tuft of brownish hairs in the collar region of the leaves. This feature is absent from the plants found in Antwerp which may point at an extra-European origin.
Selected references
Aoki D. & Yamaguchi H. (2008) Genetic relationship between Echinochloa crus-galli and Echinochloa oryzicola accessions inferred from internal transcribed spacer and chloroplast DNA sequences. Weed Biology and Management 8(4): 233-242.
Costea M. & Tardif F.J. (2002) Taxonomy of the most common weedy European Echinochloa species (Poaceae: Panicoideae) with special emphasis on characters of the lemma and caryopsis. Sida 20: 525-548. [available online at: https://archive.org/details/biostor-159424]
Mennan H. & Kaya-Altop E. (2012) Molecular Techniques for Discrimination of Late Watergrass (Echinochloa oryzicola) and Early Watergrass (Echinochloa oryzoides) Species in Turkish Rice Production. Weed Science 60(4): 525-530.
Yabuno T. (1976) Cytological relationship between the Kenyan diploid strain of Echinochloa pyramidalis (Lamk.) Hitchc. et Chase (n = 9) and E. oryzicola Vasing. (n = 18). Cytologia (Japan) 41(3-4): 679-684. [available online at: https://www.jstage.jst.go.jp/article/cytologia1929/41/3-4/41_3-4_679/_pdf]
Yabuno T. (1983) Cytogenetical studies on the hybrids of Echinochloa oryzicola Vasing and the Thai tetraploid strain of E. stagnina (Retz.) Beauv. with the West African species E. obtusiflora Stapf. Cytologia (Japan) 48(3): 597-604. [available online at: https://www.jstage.jst.go.jp/article/cytologia1929/48/3/48_3_597/_pdf]
Yamasue Y. (2001) Strategy of Echinochloa oryzicola Vasing. for survival in flooded rice. Weed Biology and Management 1(1): 28-36.