Distinct numerical variation of B-chromosomes among different tissues in Aegilops mutica Boiss

This is the first report on the numerical variation of B-chromosomes (Bs) in Aegilops mutica based on the detailed cytological observations in different tissues of the same individuals. A total of 30 plants with 0B to 4Bs were examined in the seminal roots, adventitious roots, shoot apices and/or pollen mother cells (PMCs). Bs were stably found in the shoot apices and PMCs, while they were almost entirely absent from both the seminal and adventitious roots. Judging from this result, it was concluded that Bs of Ae. mutica were stably maintained in the germ line cells from fertilization to the beginning of meiosis. Further, it was suggested that they were eliminated during one or a few cell divisions at a specific stage of root differentiation, probably at an early stage of embryogeny for seminal roots and at an early stage of differentiation of adventitious roots from a central cylinder.