The structure, meiotic behaviour and effects of B chromosomes inBriza humilisBieb. (Gramineae)

✍ Scribed by B. G. Murray

• Publisher: Springer Netherlands
• Year: 1984
• Tongue: English
• Weight: 761 KB
• Volume: 63
• Category: Article
• ISSN: 0016-6707
• DOI: 10.1007/bf00128415

✦ Synopsis

A single population of Briza humilis contained two types of B chromosome, one a large ( BL) and the other a small (Bs) acrocentric. DNA measurements show that the BL chromosome contains approximately twice as much DNA per unit length as the members of the regular complement. The meiotic pairing behaviour of the Bs is variable and BL and BS are seen to pair in some cells. The presence of BL depresses the chiasma frequency of the regular complement but the chiasma frequency of A and B chromosomes does not appear to be related. The transmission rate of the B chromosomes is variable and the BL shows a non-disjunction mechanism during microsporogenesis that is absent during megasporogenesis. For the BS chromosome the transmission rate is very low and there is no evidence of a non-disjunction mechanism. In general seeds containing BL chromosomes germinate more slowly than those without B chromosomes.