Cytogenetical Studies of the Bothriochloa intermedia Complex

Abstract

1. A cytogenetic study of the members of the Bothriochloa intermedia was made from several geographic locations of the world. The most common chromosome number was 2n=40, however, plants with 2n=50, 60, and 80 chromosomes were also encountered. B. longifolia which is very closely related to B. intermedia has 2n=20 chromosomes.
2. Presence of univalents, bivalents, trivalents, quadrivalents, bridges, and fragments at meiosis indicate hybridization as well as chromosomal interchanges. The plants behave as segmental allopolyploids.
3. Aneuploids though present in the artificially produced populations are absent in the natural populations, indicating a lack of survival in nature in competition with plants having complete genomic constitution.
4. Polyploid B. intermedia complex is widely distributed in the tropics and sub-tropics of the world, and shows a greater ecological plasticity than the diploid relatives which have restricted geographic and ecological distribution.
5. Polyploidy in the B. intermedia apparently is due to large scale hybridization made possible through apomixis and preferential pairing of chromosomes. B. intermedia is another group where apomixis is correlated with polyploidy.