Differential Fluorescent Banding in Gossypium hirsutum L. and Two Forms of G. arboreum L.

Abstract

The somatic chromosomes of Gossypium hirsutum, G. arboreum brown form, and G. arboreum white form were studied after staining with orcein, chromomycin A3 (CMA) and DAPI. Gossypium hirsutum possessed 2n=52 chromosomes with a gradual decrease in chromosome length. Both the forms of G. arboreum showed 2n=26 chromosomes with no such sharp decrease in chromosome length. The centromeric formula of G. hirsutum was 20 m+32 sm. The centromeric formulae of 10 m+16 sm and 14 m+12 sm were determined in the brown and white form of G. arboreum, respectively. Two big and 4 small CMA-positive bands were found in G. hirsutum. Four CMA-positive bands were found in G. arboreum brown form. The individual size of the band in the brown form was similar to that of big bands in G. hirsutum. Three CMA-positive bands were observed in the white form of G. arboreum which were smaller than those of the brown form. Gossypium hirsutum showed 3 DAPI-positive bands whereas no DAPI-positive band observed in brown and white form of G. arboreum. In G. hirsutum, 6 DAPI-negative bands appeared at the same location where CMA-positive bands were present. Three DAPI-negative bands were observed in brown and white form of G. arboreum at the same location where CMA-positive bands appeared. Reversible banding indicated the presence of GC-rich repeats. The banding pattern of G. hirsutum appeared to consider it as segmental allopolyploid. In spite of some similarities, the 2 forms of G. arboreum possessed unique fluorescent banding features.