Abstract
The cytology of a number of morphologically similar Bothriochloa species was studied. The Australian B. decipiens (2n=40) and B. ambigua (2n=60) are morphologically allied, sexually reproducing allopolyploids based on n=10. The Indian endemic B. longifolia is a sexually reproducing diploid. The remaining species studied are gametophytic apomicts, and behave cytologically like segmental allopolyploids. Tetraploid and hexaploid races characterize B. pertusa. Cytological and morphological data indicated that the hexaploids originated from the fertilization of a cytologically unreduced gamete. Bothriochloa radicans and B. glabra are tetraploids, while B. insculpta is characterized by pentaploid and hexaploid races. Morphological data indicated that hexaploid B. insculpta could have originated from a cross between plants resembling B. radicans and B. glabra. These hexaploids are of two morphological types, and it was proposed that the one combines the complete chromosome complement of B. glabra and the haploid complement of B. radicans, while the other originated from fertilization of the cytologically unreduced gamete of B. radicans. Pentaploids apparently represent backcross populations to either parent.
