Cytological relationship between the Kenyan diploid strain of Echinochloa pyramidalis (Lamk.) Hitchc. et Chase (n=9) and E. oryzicola Vasing. (n=18)

Echinochloa oryzicola (n=18) is an annual self-pollinated species distributed in north-east Asia and Italy as a weed in lowland rice fields. E. crus-galli (n=27) distributed widely in the world is also an annual and self-pollinated species. Cytogenetically the latter species has been assumed to be an allohexaploid derived from the natural hybridization between the former species and an unknown diploid species of the genus Echinochloa or a related genus followed by chromosome doubling. The diploid strain of E. pyramidalis was found in Kenya by the author in 1968. The discovery of the diploid strain deserves the great attention for deter-mination of the origin of hexaploid species, E. crus-galli. The Kenyan diploid strain of E. pyramidalis is a cormous perennial and is partially self-incompatible. Chromosome association at MI of the F1 hybrid between E. oryzicola and the Kenyan diploid plant of E. pyramidalis showed that the genome of the diploid plant may be related to one of the two genomes of E. oryzicola. The F1 plant was a cormous perennial and quite sterile.