In this study, 11 perennial strains of wild Echinochloa species from Africa were mainly treated biosystematically. It could be confirmed that one strain from Kenya has 2n=18, one strain from Kalahari has 2n=90, and of seven strains from Mali, two have 2n=54, one has 2n=63 and four have 2n=72. One strain from Nigeria has 2n=36 and one strain from Northern Cameroun has 2n=72. According to the routine taxonomic system of the genus Echinochloa, these strains have been identified as either E. stagnina or E. pyramidalis.
All these strains are tolerable to flooding condition. Among them, West African strains were collected in the inundated area, where floating varieties of Oryza sativa and O. glaberrima were grown.
Perennial 4X(2n=36) and 14X(2n=126) strains of E. stagnina were found in West Bengal and Assam, respectively, and an annual 12X(2n=108) strain of this species was in the northwest of Western Australia.
On the basis of the results of morphological and cytological studies on the strains which have been identified either as E. stagnina or E. pyramidalis, it is considered that the taxonomic status of these two species are not well established so far. In order to grasp the intrinsic nature of the wide variations recognized in E. stagnina and E. pyramidalis and to elucidate the relationships among the chromosomal races of these two Echinochloa species, the cytogenetical investigations are required to be done.
The present investigation was facilitated by receiving the valuable materials from Drs. H. I. Oka and W. T. Chang. Their kind cooperation is cordially appreciated.