Barley chromosome arms longer than half of the spindle axis interfere with nuclear divisions.

We have tested the influence of recombinantly-elongated chromosome arms on nuclear divisions in barley and confirmed a rule according to which half the length of the average spindle axis defines the upper tolerance limit for chromosome arm length. A slightly longer chromosome arm caused incomplete separation of sister chromatids in approximately 70% of mitotic telophase cells and >2.5% of daughter cells showing a micronucleus, due to disruption of non-separated sister chromatids by the newly forming cell wall. In homozygous condition, this elongated chromosome mediated a slower growth and reduced fertility of the carrier plants. Its meiotic transmission was not impaired because of the larger spindle dimensions in meiocytes as compared to those in mitotic cells. Copyright 2002 S. Karger AG, Basel