Permanent Translocation Heterozygosity and Sex Determination in East African Mistletoes

Viscum fischeri has 2n = 23 chromosomes in male plants. These form 7 bivalents and a translocation chain of 9 chromosomes during meiosis. Pollen with 11- and 12-chromosome genomes is thus produced. Female plants have 2n = 22 chromosomes and produce 11 bivalents during meiosis. Sex deter- mination is technically a rare multiple X-multiple Y type, but more importantly it provides the mechanism whereby permunent translocation heterozygosity is maintained in the system. In a second species, Viscum engleri, male plants have Abstract. Viscum fischeri has 2n = 23 chromosomes in male plants. These form 7 bivalents and a translocation chain of 9 chromosomes during meiosis. Pollen with 11- and 12-chromosome genomes is thus produced. Female plants have 2n = 22 chromosomes and produce 11 bivalents during meiosis. Sex deter- mination is technically a rare multiple X-multiple Y type, but more importantly it provides the mechanism whereby permunent translocation heterozygosity is maintained in the system. In a second species, Viscum engleri, male plants have