B-chromosomes in Iseilema laxum Hack. I. Cytology

Upto 6 B-chromosomes occurred in natural populations of the fodder grass Iseilema laxum Hack. They were smaller than the A-chromosomes and stained darker. Although the number of B's varied in different PMC's of even the same anther presumably due to the phenomena of nondisjunction and precocious divisions, it was possible to assign a definite number to a particular plant. As seen from pachytene morphology, three types of B's were seen. More than one type can also occur in the same plant. Pairing can take place between homo-as well as heteromorphic B's resulting in bivalents. B-chromosomes in Iseilema laxum appear to have a common origin.