Heterochromatin distribution and comparative karyo-morphological studies in Vigna umbellata Thunberg, 1969 and V. aconitifolia Jacquin, 1969 (Fabaceae) accessions

Abstract. Chromosome studies along with heterochromatin distribution pattern analysis have been carried out in two domesticated species of Vigna Savi, 1824 which grow in contrasting geo-climatic conditions of India: Vigna umbellata Thunberg, 1969, a legume well acclimatized to subtropical hilly regions of North-east India and Vigna aconitifolia Jacquin, 1969, a species of arid and semi-arid regions in desert plains of Western India. Karyo-morphological studies in both species reveal 2n = 22 chromosomes without any evidence of numerical variation and the overall karyotype symmetry in chromosome morphology suggest that the diversification at intraspecific level in genus Vigna has occurred through structural alteration of chromosomes, rather than numerical changes. Heterochromatin distribution as revealed by fluorochrome binding pattern using CMA(3) and DAPI, confirms the occurrence of relatively more GC content in Vigna aconitifolia as compared to Vigna umbellata. However, AT content was found to be comparatively higher in Vigna umbellata which perhaps play a role in species interrelationships.