CHARACTERISATION OF ANTHOCYANINS FROM RADIATION INDUCED BLACK AND GREY SEED COAT MUTANTS OF COWPEA

Abstract

The presence of natural compounds like chlorophyll, carotenoids, flavonoids and polyphenols determines the colour of plant parts including seed coat. A correlation is often found between the content of these compounds and the seed coat colour. Ishikura et al. [1] reported the presence of an anthocyanin, delphinidin-3-glucoside in the black seed coat of urdbean. Pandey et al. [2] found three anthocyanin compounds in the black seed coat of mungbean cv. RUM-5. Anthocyanins have also been extracted and separated from the seed coat of black soybean[3]. The germplasm collection of cowpea (Vigna unguiculata (L.) Walp) exhibits variations in seed coat colour ranging from pure white, yellow, green, brown, grey, stippled black to dark black. Variations in seed coat colour have also been brought about by induced mutations. Sharma[4] obtained stippled black, brown and other seed coat colour mutants from the white seeded cultivar Pusa Phalguni following mutagenic treatments owing to mutator system. The cowpea varieties V-16 and V-240, both with brown seed coat colour, are the mutants selected from the stable lines following treatment of white seeded Pusa Phalguni with 0.8% DMS [5, 6]. Pandey and Pawar[7} obtained several seed coat colour mutants including stippled black, grey, brown, yellow and light green in addition to partially coloured testa following irradiation of a white seeded cultivar V-130 of cowpea. The stippled black and grey mutants showed instability in seed coat colour in subsequent generations. The present investigation was undertaken to find out the presence of anthocyanins in the coloured testa of the mutants, especially in the stippled black and grey seed coat. A local cowpea genotype, Ratnagiri local (RL), characterised with jet-black seed coat was also included in the investigation.