INTRODUCTION Mungbean is an important short duration (65-90 days) legume crop of high nutritive values. It maintains soil fertility through biological nitrogen fixation in soil and thus plays a vital role in sustainable agriculture (Kannaiyan, 1999). Protein malnutrition remains a major nutrition problem in Asia and affects children most severely (WHO, 2000). Mungbean is a cheap source of protein and important nutritious dietary component of vegetarians in Asian countries especially in South- East Asia (Keatinge et al., 2011). Salinity is a main constraint in the production of mungbean where, 50 M NaCl can cause yield losses up to 70 % (Saha et al., 2010). Higher accumulation of salt decrease the osmotic potential of soil solution causing water stress in plants and further interactions of the salts with mineral nutrition cause nutrient imbalance and deficiencies, oxidative stress ultimately leading to plant death as a consequence of growth arrest and metabolic damage (Zhu, 2001; Tavakkoli et al., 2010; Hasanuzzaman et al., 2012). Salt stress alters plant growth and morphology, photosynthetic capacity, cell membrane integrity, cellular enzyme protection system and many physiological and biochemical activities (Chen et al., 2007). Levels of proteins, secondary metabolites, osmolytes, photosynthetic pigments, membrane damage and antioxidants were reduced at higher salt concentrations increased under salinity (Mankar et al., 2021). A study on variability among available genotypes is the pre-requisite for initiating a varietal development programme. Hence, it is necessary to analyses the nature and magnitude of the heritable genetic variation present among the genotypes. D-value represent the salinity stress index was used to find out the most tolerant genotype of mungbean. Mankar et al., (2021) reported that germination and early seedling stage was more authentic to identify salt-tolerant mungbean varieties. The crosses between parents with maximum genetic diversity were generally the most responsive for genetic improvement (Arunachalam, 1981). An attempt was made to evaluate mungbean genotypes for their reaction to salt stress and to assess the genetic variability for salinity tolerance. Due to complex nature of salinity stress and lack of appropriate techniques for introgression less progress has been made in developing salt stress varieties (Singh and Singh, 2011). Therefore, the general objective of this study was to assess the genetic variability and identify the salinity tolerant genotypes among some mungbean genotypes. MATERIALS AND METHODS A laboratory experiment during Kharif (2018-19) was carried out at Department of Plant Breeding and Genetics, S.K.N. College of Agriculture, Jobner at 32.3°C temperature and 53 % relative humidity. The seeds of 10 genotypes of mungbean viz., RMG-1095, RMG-1078, RMG-975, MSJ-118, RMG-976, RMG-1101, MVM-2, RMG-1079, RMG-1099 and RMG-492 were surface sterilized by using 0.1 % mercuric chloride followed by three time rinsing with tap water. The three salinity levels were 0.0 % (control), 0.2 % and 0.4 % NaCl created by supplementing 0, 2 and 4 g NaCI to 1000 ml of double distilled water, respectively. The experiment was carried out in completely randomized design (CRD) with three replications. The observations were taken on 17th day after sowing. The methods used for recording observations are described below: A seed was considered as germinated at the emergence of both radicle and plumule up to 2 mm length (Chartzoulakis and Klapaki, 2000). The germination was recorded on 7th day of planting and germination percentage (GP) was determined by using the following formula (Aniat et al., 2012). On 17th day observations taken on various seedling characters viz; shoot length, root length, seedling length, shoot fresh weight, root fresh weight, seedling fresh weight, shoot dry weight, root dry weight, seedling dry weight. The root length/ shoot length ratio of seedling was calculated by the following formula. "Root length/Shoot length ratio = " RL/SL The seedling vigour index was determined by the following formula (Iqbal and Rahmati, 1992): Seedling vigour index (SVI) = (RL+SL) × (GP) D – Value. This represents salinity stress intensity and was derived by following formula: "D=1- " "Y" _"j" /"Y" _"c" Where, Yj = Mean performance of a concerned character of all the genotypes in the salt stress environment Yc = Mean performance of a concerned character of all the genotypes in the normal environment The data obtained were subjected to analysis of variance following standard statistical methods (Panse and Sukhatme 1985) and the significant difference among the mean value were compared by least significant difference (LSD) test (P<0.05). Variability parameters were calculated by using various formulae given by Burton (1952); Johnson et al. (1955). RESULTS AND DISCUSSION The pooled ANOVA of mungbean genotypes showed significant difference among the genotypes and all salinity levels for all the characters, indicated that genotypes showed differential response to different salinity levels (Table 1). Similar findings were also reported by Gogile et al., (2013), in lentil by Tesfaye et al. (2015), in munbean by Hapsari and Trustinah (2018) for most of the characters. In mungbean all the characters under study showed variation at different levels of salinity (Table 2). Variability parameters for germination percentage were higher at highest salinity level (Fig. 1). Similar variation for germination percentage was reported by Kandil et al. (2012); Sehrawat et al., (2014); Kamrul et al., (2018) in mungbean. Variability parameters were increased with advancement of salinity levels in mungbean for germination percentage and seedling characteristics viz., root length (Fig. 2), shoot length (Fig. 3), seedling length (Fig. 4), shoot fresh weight (Fig. 5), root fresh weight (Fig. 6), seedling fresh weight (Fig. 7), root dry weight (Fig. 8), shoot dry weight (Fig. 9), seedling dry weight (Fig. 10) root length/shoot length ratio (Fig. 11) and seedling vigour index (Fig. 12) and similar results were widely reported in mungbean (Subashree et al., 2021); (Swarnakar, 2016), in lentil, chickpea and faba bean (Arslan et al., 2016), in cowpea (Haleem, 2015), in Pisum sativum var. abyssinicum and Lathyrus sativus (Tsegay and Gebreslassie 2014), in moth bean and mung bean (Saroj and Soumana 2014). In general PCV were higher than GCV for all the characters indicating a positive effect of environment on the expression of characters. The highest GCV was obtained in root dry weight followed by root fresh weight and root length and highest PCV was obtained in root dry weight followed by root fresh weight and root length. Lowest GCV was obtained for shoot length followed by germination percentage and seedling length and lowest PCV was obtained for seedling length followed by shoot length and root length/shoot length ratio across the salinity gradients. Huda et al., (2017) in rice under saline condition reported higher percentage of GCV and PCV for root dry weight. Kumawat and Gothwal (2018) reported lowest GCV for germination percentage which was similar with investigated results. Heritability in broad sense was generally increased with increasing salinity level for germination percentage, seedling length, seedling fresh weight, shoot dry weight, root length/shoot length ratio and seedling vigour index. Characters having high heritability were not more affected by the environment (Chen et al., 2007). Increase in heritability with increased salinity level indicated that variability was increased as advancement in salinity level due to expression of gene for salinity tolerance (Saranga et al., 1992; Foolad 1996; Khan et al., 2003). Increasing trend in genetic advance with increasing salinity level for most of the traits indicated that higher variability was obtained at higher salinity level therefore; selection at higher salinity level is more responsive for obtaining salinity tolerant genotypes (Kumawat and Gothwal 2018; Gupta 1994). On the basis of D-value (Table 3) the characters shoot dry weight was the most sensitive under salinity. It is suggested that major emphasis should be given on shoot dry weight while screening for salinity tolerance. According to reduction in mean value of shoot dry weight as compared to control genotypes (Table 4) mungbean genotypes MVM-2 is more tolerant to salinity followed by RMG-1099 and RMG-1101.