Echinochloa oryzicola (Vasinger) Vasinger, Fl. SSSR 2: 33. 1934.

Hoste, Ivan & Verloove, Filip, 2022, Taxonomy of the weed species of the genus Echinochloa (Poaceae, Paniceae) in Southwestern Europe: Exploring the confused current state of affairs, PhytoKeys 197, pp. 1-31 : 1

Echinochloa oryzicola (Vasinger) Vasinger, Fl. SSSR 2: 33. 1934.

= Echinochloa phyllopogon auct., non (Stapf) Stapf ex Kossenko in Botanicheskie Materialy Gerbariia Botanicheskogo Instituta imeni V. L. Komarova Akademii Nauk SSSR 8(12): 208. 1940.

= E. hostii auct. ital., non (M. Bieb.) Link, Hort. Berol. 2: 209. 1833.

Basionym.

Panicum oryzicola Vasinger, Trudy Prikl. Bot. 25(4): 125. 1931.

Type.

Vladivostok region , left bank of Santakheza, 4 km east of Lake Hanka, 23 Aug 1928, A. Venzinger-Alexandrova (lectotype, designated by Tzvelev 1976: 664, LE01010882). Image available at http://herbariumle.ru/?t=occ&id=15824&rid=image_0036250 .

Remarks.

Although sometimes included in E. crus-galli , several features justify accepting E. oryzicola as a separate species. Echinochloa oryzicola is tetraploid (2n = 36), whereas E. crus-galli is hexaploid (2n = 54) ( Yabuno 1966, 1981). The length of the embryo is a reliable feature to distinguish E. oryzicola from E. crus-galli var. Echinochloa crus-galli oryzoides (which also has large spikelets) and from specimens of the very poorly defined E. crus-galli var. hispidula . If carefully applied, the shape of the mature inflorescence and the length of the lower glume may help separate it from E. crus-galli var. oryzoides . It is rather surprising that the seemingly distinctive feature of the length of the lower glume is not mentioned in Vasinger’s original description (Vasinger in Komarov 1934).

Yabuno (1966) distinguished two morphological forms of E. oryzicola : the F-form, in which the lemma of the sterile flower is flat and has a coarse surface texture, and the C-form, in which the lemma is convex, coriaceous and shiny. The latter form has only rarely been recorded from Southwestern Europe. Specimens with spikelets much too small for E. oryzicola but with a lemma that morphologically closely resembles Yabuno’s C-form have been recorded from Germany (as E. crus-galli subsp. spiralis ; Scholz 2002) and Belgium (IH, unpublished records).

The treatment of the rice mimics E. oryzicola and E. crus-galli var. oryzoides in taxonomic and agronomic publications has been extremely confusing. In the past, the name E. phyllopogon , often without author citation and thereby adding to confusion, was used separately for each of the two taxa as well as for both of them together; see, e.g., the shifting interpretation in successive publications by Michael (1983, 1994, 2001) and Yabuno’s (1981) discussion of European E. phyllopogon as a synonym for E. oryzicola . Echinochloa phyllopogon is a very confusing name, whose identity has been recently summarised and discussed by Crespo et al. (2020a). Its basionym, Panicum phyllopogon , was described by Stapf (1901). The accompanying plate shows a specimen that seems to combine features of at least two species. It was said to have been collected by Arcangeli in rice fields near Pisa (Italy). Arcangeli’s herbarium is located in PI and FI, at least for the most part. A targeted search in the Arcangeli Herbarium (PI-ARC) did not yield any Echinochloa specimen collected in the rice fields near Pisa (comm. F. Roma-Marzio, 09.2018). In the Herbarium Generale of PI, there is a specimen labelled as P. phyllopogon , which was part of Flora Italica Exsiccata. The herbarium label states that this species was collected in Italy for the first time in Novara and that Stapf erroneously indicated it to be from Pisa. In fact, the species was collected by Jacometti near Novara but was originally, erroneously so, attributed to a collection of Arcangeli from near Pisa (comm. N. Ardenghi 10.2018). A lectotype for this name was designated by Kossenko (1940) based on one of Jacometti’s collections (K000958854; image available at http://www.kew.org/herbcatimg/638594.jpg). This collection includes both vegetative and flowering material that, according to P.W. Michael, refers to two different species. The non-flowering part, with very characteristic hair tufts at the junction of leaf blade and leaf sheath, was said to represent P. phyllopogon and was recommended to serve as (second step) lectotypification for that name ( Michael 1983). However, the presence or absence of such hair tufts is a non-diagnostic feature that can be observed (although not so frequently) in various species of Echinochloa , including E. oryzicola and E. crus-galli var. oryzoides . Since both these taxa occur in the Novara area in Italy, it is impossible to assign Stapf’s P. phyllopogon to one of these taxa. Therefore, it is a confusing name that should be abandoned. However, lectotypification of P. phyllopogon was effected later by Kossenko (1940) himself, though under the combination " E. phyllopogon subsp. stapfiana Kossenko", a superfluous, illegitimate name that explicitly included the type of the species (subsp. Echinochloa phyllopogon phyllopogon ). Crespo et al. (2020a) argued this lectotype is to be followed; this made the later lectotype proposal by Michael (1983) ineffective. Consequently, E. phyllopogon should be included as synonymy of E. oryzoides , as suggested by Crespo et al. (2020a) and Martínez-Azorín and Crespo (2021).

The separate status of E. oryzicola has been corroborated by molecular studies (e.g., Yamaguchi et al. 2005; Ye et al. 2014), although Yasuda and Nakayama (2019) have shown that relying solely on cpDNA may result in misidentification of E. crus-galli var. formosensis as E. oryzicola .

Unfortunately, the structure of the tip of the fertile lemma, which clearly distinguishes E. crus-galli from E. muricata ( Hoste 2004), has received little attention in studies on the weed flora of rice fields in Europe and Asia. In E. oryzicola , the tip more closely resembles E. crus-galli , although the line of tiny hairs is usually more difficult to see than in E. crus-galli (based on specimens from Italian rice fields seen by us; Fig. 4A ).

Figures

Figure 4. Spikelets of Echinochloa oryzicola A fertile lemma with the tip differentiated from the coriaceous body of the lemma (upper glume removed) B, C two spikelets with convex shiny sterile lemma D spikelet with long lower glume and non-shiny sterile lemma. (Photograph: Andre De Kesel, Meise Botanic Garden).