Fluorescent-banded karyotype analysis and identification of chromosomes in three improved Indian varieties of grass pea (Lathyrus sativus L.)

Abstract

Karyotype analysis of three improved grass pea (Lathyrus sativus L.) varieties, namely Nirmal, BioL-203 and BioR-231 was carried out using root tip metaphase cells after staining with orcein and with two DNA base specific fluorochromes, Chromomycin A3 (CMA) and 4-6'diamidino 2-phenyle indole (DAPI). It was revealed that the three varieties were diploids showing 2n=14 with metacentric and submetacentric chromosomes. The three varieties showed minor variations in conventional orcein staining, but were distinctly different from each other in GC-specific CMA and AT-specific DAPI-banding patterns. CMA-stained regions fluoresced as bright bands mainly in terminal secondary constriction and peri-centromeric regions, while DAPI-stained parts were highlighted both as bands and pairs of dots in terminal regions of different pairs. The study revealed conspicuous differences among seven pairs of chromosomes and presence of one pair of chromosomes with secondary constriction, pair 1 in BioR-231 and pair 2 in both BioL-203 and Nirmal, containing GC-rich repeats. Among the varieties, Nirmal contained the highest percentage of GC-rich sequences exhibiting 12 CMA-positive bands, and it was followed by BioL-203 (10 bands) and BioR-231(eight bands). In DAPI-banding, the highest number of bands (12) was scored in BioL-203, followed by BioR-231 (10) and Nirmal (eight). The variation in banding patterns suggests the presence of karyomorphological polymorphism in the present materials.