In diploid and autotetraploidDactylis glomeratassp.lusitanicaand its allo-tetraploid hybrids withD. glomeratassp.glomerata, B-chromosomes undergo non-disjunction and preferential segregation to the generative nucleus at first pollen mitosis. This results in transmission by male gametes of double the number of B-chromosomes received by the microspore at completion of meiosis. This mechanism of numerical increase is similar to that reported for a number of other species of Gramineae. On the female side, transmission of B-chromosomes is normal.
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