Accessory Chromosomes in a New Hexaploid Species ofPanicum

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Abstract
The occurrence and meiotic behaviour of accessory chromosomes in a newly-delineated species of Panicum, viz., Panicum nehruense Jauhar et Joshi, are reported in this paper. As many as 24 accessories were observed apart from the normal complement of 2 n=54 chromosomes. Mosaicism in number of accessory chromosomes, as also of the normal ones, was encountered in the taxon. Numerical variation of the accessories was attributed to somatic elimination and/or somatic non-disjunction during the premeiotic mitotic stages. Some degree of pairing between the accessory chromosomes, upto bivalent level, was noticed. On the basis of a number of characters which the accessory chromosomes have in common with the normal chromosomes, coupled with the secondary association of the former with the latter at metaphase I, it was inferred that the accessory chromosomes may have originated from the normal chromosome complement, and presumably from different genomes, in this allohexaploid taxon.