XVI International Botanical Congess

B chromosomes are found in hundreds of plant species. Their maintenance in populations depends upon properties that foster their accumulation, often involving nondisjunction of the centromere. Our lab has cloned a degenerate repeat specific to the B chromosome centromere that we are using to study its organization and function. The natural phenomenon of misdivision of the centromere was used to reduce the size of the B centromere. Meiotic transmission is not dramatically affected until the size falls below about one megabase, although chromosomes with centromeres less than 300 kilobases in complexity can still be recovered. The potential for the use of the small centromere derivatives of the B chromosome for the construction of maize artificial chromosomes will be discussed.