Abstract

The accessory chromosome of Sorghum nitidum appeared to be an iso-chromosome that exhibited considerable inter-arm pairing at pachytene. The centromere misdivision and subsequent structural changes of the nucleolus associated chromosome is postulated as the possible mechanism for the origin of the accseeory chromosome in S. nitidum. In microsporocytes, the accessory chromosomes usually divided equally at AI and the members, though often lagging, eventually move to the opposite daughter nuclei. But the accessory chromosomes are often eliminated from the somatic tissues. In the plants with one accessory chromosome, a low frequency of bridges with fragments at AI was observed. This fact indicates that the accessory chromosomes may possible induce the paracentric inversion and crossing over within the inversion loop in the A-chromosomes. The accessory chromosome seems to have a slightly retarding effect on growth vigour.