INTRODUCTION Blackgram [Vigna mungo (L.) Hepper] being autogamous in its floral morphology is positioned in family Fabaceae (sub family: Papilionaceae) with chromosome number 2n=2x=22 is one of the dominant Asiatic leguminous crop. It is commonly called as urd, urdbean or mash and its estimated genome size is 574Mbp (Jegadeesan et al., 2021). It is a pulse of tropical and sub-tropical areas and potentially grown in many countries (Girish et al., 2012). In India, its cultivation is taken up in all the cropping seasons i.e. Rabi, Kharif and Zaid. One of the major factor that has given fame to this crop is its adaptability in crop rotation with various crops and its suitability in both rainfed and irrigated conditions (Singh et al., 2020). Regarding nutritional aspects of blackgram, it shows its richness in protein content i.e. (20-25%). It also contains other proteins such as albumin and globulin along with amino acids like lysine and tryptophan. It also has fat (1.4%), minerals (3.2%), fibre (0.9%) and carbohydrate (59.6%). Apart from this, its seeds are rich in vitamins like thiamine, riboflavin and niacin. When the existing UPOV models for plant variety protection could not meet requirements of India, the Government of India had to enact its own legislation popularly known as “Protection of Plant Varieties and Farmers Right Act (PPV&FRA) in 2001 with an aim of providing protection to the plant varieties on the basis of their distinctiveness, uniformity and stability (DUS) examination. This act apart from novelty carries a uniqueness of maintaining equality between the breeders and the farmers treating them as partners in their attempts of food security. There are several steps that the process of varietal identification includes and they are identification a variety, confirmation of a variety, distinctness of a variety from all other, purity of the variety and characterization of a variety as per their descriptors (Rao et al., 2013). The DUS testing either in field or glasshouse is generally employed for two successive seasons as per the protocols given by PPV&FRA. Morphological markers are inexpensive in nature, quick to score and have high heritability and therefore they are employed in morphological characterization (Kumawat et al., 2020). Morphological characterization groups the germplasm/genotypes/varieties possessing specific traits that brings out a clear differentiation from one another. Piyada et al. (2010) also emphasized on morphological characterization in order to check variability and differentiate between the crop germplasm. MATERIALS AND METHODS The experimental material comprised 40 diverse blackgram genotypes received from the Department of Plant Breeding and Genetics, College of Agriculture, Jawaharlal Nehru Krishi Vishwavidyalaya, Jabalpur, Madhya Pradesh, India. The field trial was conducted during Summer-Kharif 2021 in randomized block design in 3 replications. The genotypes were planted in four rows of 2 meters each maintaining a row to row distance of 40 cm and plant to plant distance of 10 cm. The morphological observations under study were recorded at the stages as per the guidelines for the conduct of Test for Distinctiveness, Uniformity and Stability on Blackgram [Vigna mungo (L.) Hepper] by PPV&FRA. The anthocyanin colouration of hypocotyl was observed when the cotyledons were unfolded i.e. 5-6 days after sowing. The time of flowering was recorded when the 50% of the plants possessed at least one open flower. The plant growth habit, the plant habit, stem colour, stem pubescence, leaflet (terminal) shape, foliage colour, leaf vein colour, leaf pubescence were observed at 50% flowering stage. At the stage of fully developed green pods, the characters petiole colour, intensity of green colour of premature pods were noted. The pod length was taken up at harvest maturity while the seed colour, seed lusture, seed shape and seed size (weight of 100 seeds) were noted down in mature seeds i.e. after harvesting. RESULTS AND DISCUSSIONS Characterization forms a pre-requisite in varietal identification and the results of the same which includes grouping as well as frequency distribution of blackgram genotypes has been provided in the (Table 1&2) coupled with its discussion in this section. Hypocotyl: Anthocyanin colouration. This trait acts as an important morphological marker and can be effectively employed for varietal identification prior to active seed multiplication. Anthocyanin colouration recorded at seedling stage was present in all the 40 blackgram genotypes under observation indicating no variation for this trait. Similar finding was reported by Singh et al. (2020). Flower character. Time of flowering was examined when 50% of the plant had at least one open flower bud. It was grouped in three categories viz. early (<40 days), medium (40-50 days) and late (>50 days). 32 genotypes were early in their time of flowering and 8 were medium while of the genotypes were late in their time of flowering (Table 1). The early the genotypes are the more is the tendency in them to mitigate the abiotic stresses during their reproductive stage (Pratap et al., 2013). Jain et al., (2002) reported the usefulness of flower characteristics in characterization of greengram germplasm. Plant characters. Plant growth habit and plant habit were studied at 50% flowering stage. Among 40 genotypes, 5 erect, 9 semi-erect and 26 spreading were in their growth habit while concerning plant habit, 8 determinate and 32 indeterminate genotypes were reported in the present investigation of characterization significant amount of variation these traits (Table 1). Erect types are prime importance as they receive good amount of sunlight which speeds up the assimilate production in the plant. Singh et al., (2020) also reported significant variation in their findings in blackgram and Singh et al. (2014) in mungbean. Stem characters. This character included two traits viz. stem colour and stem pubescence observed at 50% stage of flowering. The colour of stem out 40 genotypes were purple with green splashes for 31, green with green splashes for 5, purple for 4 genotypes and 0 for none of the genotypes respectively whereas stem pubescence was present in all the genotypes showing no variation (Table 1). Leaf characters. These characters influence the yielding ability of genotypes because leaves directly participate in photosynthesis. Leaf characters included leaflet (terminal) shape, foliage colour, leaf vein colour and leaf pubescence which were noted at 50% stage of flowering. All the genotypes varied significantly for leaf morphology except for leaf pubescence because it was present in all the genotypes showing no variation (Table 1). The purple leaf vein colour was present in one genotype i.e. IPU 2-43 with a frequency distribution of 2.5% (Table 2). Petiole colour. Petiole colour was observed at the stage when green pods were full developed. The extent of frequency distribution for petiole colour was (35%) for green and (26%) for green with purple splashes colour respectively (Table 2). (Singh et al. 2020) also showed significant variation for petiole colour in blackgram genotypes. Pod characters. Pod characters are one of the important attributes in blackgram as well as greengram and play a chief role in the identification of genotypes. In this present study, the pod characters viz. intensity of green colour of premature pods, pod pubescence and pod length was observes at fully developed green pod stage. These traits varied in their morphology and were grouped into different categories. Out of 40 genotypes, 23 possessed greenish yellow pods, 15 were with green while 2 had dark green pods respectively (Table 1). In case of pod pubescence, there was no significant variation because pubescence was present in the pods of all the 40 genotypes (Table 1). Similar results were reported by Kaur et al. (2017) in mungbean. Seed characters. The traits under seed characters included seed colour, seed lusture and seed shape respectively which were observed at seed maturity i.e. after harvesting. All these characters were assigned into different groups (Table 1). The mottled seed colour was present in 28 genotypes while it was black in 8 and greenish in 1 genotype respectively. The seed colour in Uradi was greenish and its frequency distribution was 2.5% (Table 2). The seed shape for 27 genotypes was globose and oval for 11 and drum-shaped for 2 genotypes respectively (Table 1). The seed size was grouped into three categories i.e. 3 genotypes fell under large category, while 37 under medium category and none of the genotypes had small seeds (Table 1). Seed characterization is of prime importance because it enables a breeder to identify and differentiate one genotype from another while undertaking a seed production programme. Venkateswarlu et al. (2001) & Sabatina et al. (2021) discussed the importance of seed characterization in mungbean.