Analysis of Genetic Parameters for Yield, Quality and Related Traits in Mungbean [Vigna radiata (L.) Wilczek] Genotypes

Mungbean [Vigna radiata (L.) Wilczek] (2n=2x=22) also known as greengram/green bean/mash bean or golden gram belongs to the family Leguminaceae and is an excellent source of easily digestible proteins with low flatulence which complements the staple diet in Asia. Its seeds are utilized in making dal, curries, soup, sweets and snacks etc. The sprouted seeds contain a goodamount of vitamins such as Thiamine, Niacin and Ascorbic acid (Dahiya et al., 2015). Thus, mungbean sprouts are increasingly becoming popular in certain vegetarian diets. The grains contain approximately 25-28% protein, 1.0-1.5% oil, 3.5-4.5% fibre, 4.5-5.5% ash content and 62-65% carbohydrates on dry weight basis. Greengram also contains vitamin A, vitamin C, iron, calcium, magnesium, phosphorus, potassium, zinc and foliate. Unlike other pulses, it doesn’t produce flatulent effects in the stomach (Dahiya et al., 2015). Therefore, it is fed to babies and to the elders as a convalescents. Greengram is a widely cultivated crop throughout South Asia including India, Pakistan, Bangladesh, Sri Lanka, Thailand, Cambodia, Vietnam, Indonesia, Malaysia and South China. In India, it is the third most important pulse crop after chickpea and pigeonpea. It is grown mainly as a Kharif crop. However, it can be cultivated in the Rabi season as well in the eastern and southern parts of the country. It is suited for crop rotation, intercropping and mixed cropping systems owing to its short duration.
               
In any crop improvement program,the study of the amount of variability present in crop species is a pre-requisite, as it provides the basis for effective selection of desirable genotypes towards crop improvement. A clear understanding of variability in various quantitative characters existing in the breeding material helps plant breeders for selecting superior genotypes based on different genetic parameters such as genotypic variation, heritability, genetic gain, etc. to understand the nature and magnitude of variation for the available plant characters (Burton and Devane, 1953). Hence, it is necessary to estimate the relative amount of genetic and non-genetic variability exhibited by the traits under the study.  The average yield of mungbean is very low in India and year-to-year variation in yield is remarkably high. Therefore, there is an urgent need to design a breeding program that can enhance productivity and stabilize the yield. It has also been well established that the greater the genetic variability in the population greater will be the chance of obtaining desirable gene contribution. Previous studies have been in consonance with the present study with respect to greengram (Kushwaha et al., 2013, Degefa et al., 2014, Jebaraj et al., 2015, Baisakh et al., 2016 and Kumar et al., 2020) and other related pulses (Punia et al., 2014 in urdbean, Sahoo et al., 2019) in mothbean. Asthe population in the country is rapidly increasing, therefore, there is an urgent need to provide high yield varieties to meet this increasing demand. Therefore,the present study has been undertaken to study genetic variability for different quantitative characters in greengram germplasms.

The research experiment was carried out during Kharif 2017 comprising of 40 greengram genotypes at the Experimental Farm, Sam Higginbottom University of Agriculture, Technology and Sciences, Allahabad, Uttar Pradesh India (Table 1). All the genotypes to be used for present study were procured from Department of Genetics and Plant Breeding, SHUATS, Allahabad. Recommended agronomic packages of practices were followed for obtaining a good crop. The technique of random sampling was adopted for recording the observations of various quantitative characters of greengram. Five plants of each treatment from each replication were selected at random while recording the data on various characters. Data of five plants were averaged replication wise and mean data was used for statistical analysis. Observations were recorded for thirteen characters viz., days to 50% flowering (DF), days to maturity (DM), plant height (PH), number of primary branches per plant (PBP), number of clusters per plant (CPP), number of pods per plant (PPP), pod length (PL), seeds per pod (SPP), biological yield per plant (BYP), protein content (PC), seed index (SI), harvest index (HI) and seed yield per plant (SYP). Mean performance for genotypes to be used in present study has been reported earlier in International Conference (Kumar et al., 2020).


 
Macro Kjeldahl method
 
To estimate protein content, each grinded mungbean sample (1 g) was digested with concentrated sulphuric acid in the presence of cuproic sulphate and sodium sulphate and heated to release ammonia gas which is distilled into a boric acid solution. The total nitrogen persent in ammonia was estimated through titration with 0.1 M HCl until the purple-pink color was observed. The assumed nitrogen value was multiplied with a factor of 6.25 to get total protein in the sample (AOAC, 1975).
 
Analysis of variance
 
The analysis of variance (ANOVA) was worked out to test the differences among the genotypes by F-test. It was carried out according to the procedure of randomized block design for each character as per methodology advocated by Panse and Sukhatme (1985).
 
Genetic variability parameters
 
Following genetic variability parameters worked out-
 
Mean
 
Mean value of each character was worked out by dividing the totals by the corresponding number of observations.
 
Range
 
It was taken as the difference between the highest and lowest mean value for each character.
 
Components of variance
 
Two types of variance components (genetic and phenotypic variances) were calculated by the formula suggested by Burton and Devane (1953).
 
Coefficient of variations (CV)
 
It is the measure of variability evolved. The coefficient of variation is the ratio standard deviation of the variable traits to its mean and expressed in percentage which was suggested by Sivasubramanian and Madhavamenon (1973). As genotypic value is more important for crop improvement program so that CV could be divided into two part namely genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV).
 
Heritability
 
Heritability is the ratio of genotypic variance to the total variance that was calculated by the formula given by Lush (1949) and Burton and Devane (1953). Since in present study genetic variability analysed in different germplasm therefore, only broad sense heritability could be worked out.
 
Genetic advance
 
Improvement in the mean genotypic value (performance) of selected plants (progeny or lines) over the parental population (base population) is known as genetic advance which was calculated according to the formula suggested by Johanson et al., (1955).

Analysis of Variance (ANOVA)
 
Genetic variability in any crop improvement program is the basic requirement for deciding the effectiveness of selection. Its existence is essential for resistance to biotic and abiotic factors as well as for wide adaptability. The assessment of genetic variability was the main objective of the present investigation. The analysis of variance presented in Table 2 indicated that the mean squares of genotypes was significantly different at 5% level of significance for days to flower initiation, days to 50% flowering (DF), days to maturity (DM), plant height (PH), number of primary branches per plant (BPP), number of clusters per plant (CPP), number of pods per plant (PPP), pod length (PL), seeds per pod (SPP), biological yield per plant (BYP), rotein Content (PC), seed Index (SI), harvest index (HI) and seed yield per plant (SYP). The results indicated a wide range of variability among the genotypes. Similar results were recorded by Byregowda et al., (1997), Das and Chakraborty (1998), Kapoor et al., (2005), Eswari and Rao (2006), Hanif et al., (2006), Wani et al., (2009), Khan et al., (2008), Kamleshwar et al., (2013), Kushwaha et al., (2013), Degefa et al., (2014), Jebaraj et al., (2015), Baisakh et al., (2016) and Kumar et al., (2020) in greengram.
 

 
Genetic variability parameters
 
One of the important considerations in any crop improvement programme is the detailed study of genetic variability. Variability is measured by estimation of the mean genotypic and phenotypic coefficient of variation, heritability, genetic advance and genetic advance as percentage mean. Environment plays an important role in the expression of phenotype and genotype,a fact which is inferred from phenotypic observation. Hence, variability can be observed through biometric parameters like the genotypic coefficient of variation, heritability and genetic advance. This would help a breeder in evolving selection programs for genetic improvement of the crop plant.The estimates of variance, coefficient of variation, heritability and genetic advance for all the thirteen characters studied have been presented in Table 3.
 

 
Phenotypic and genotypic coefficient of variation
 
In the present investigation, it is depicted from Table 3 that in general, estimates of the phenotypic coefficient of variation were found higher than their corresponding genotypic coefficient of variation, indicating the little influence of environment on the expression of these characters. However, good correspondence was observed between genotypic coefficient of variation and phenotypic coefficient in all characters.
       
A wide range of phenotypic coefficient of variation (PCV) observed for all the traits ranged from 33.15 (number of clusters per plant) to 3.41 (days to maturity). A higher magnitude of PCV was recorded for number of clusters per plant (33.15), harvest index (24.80), the number of pods per plant (23.37), seed yield per plant (23.15), seed index (21.25) and the number of branches per plant (20.64). A moderate value of PCV was observed for the number of seed plants (17.51), plant height (15.83), biological yield per plant (14.00) and pod length (12.65). Whereas daysto 50% flowering (4.85), protein content (4.62) and days to maturity (3.41) depicted the least phenotypic coefficient of variation. Loganathan et al., (2001) recorded high Phenotypic Coefficient of Variation for number of clusters per plant and seed yield per plant and Kumar et al., (2010) also reported moderate PCV for number of seeds per plant, followed by seed yield per plant, number of pods and number of branches per plant.
       
Genotypic coefficient of variation (GCV) ranged from 32.46 (number of clusters per plant) to 3.22 (days to maturity). A higher magnitude of PCV was recorded for number of clusters per plant (32.46), harvest index (23.13), seed yield per plant (22.68), number of pods per plant (22.55) and seed index (20.22). A moderate value of GCV was observed for the number of branches per plant (19.41),the number of seed plant (16.93), plant height (15.20), biological yield (12.64) and pod length (12.07). Whereas, days to50% flowering (4.04), protein content per plant (3.70) and days to maturity (3.22) depicted the least phenotypic coefficient of variation. Sirohi et al., (2006) observed significant variability for GCV for clusters per plant, productive branches per plant, productive pods per plant, biological yield and seed yield. Kumar et al., (2010) also reported moderate GCV for number of seeds per plant, followed by seed yield per plant, number of pods and number of branches per plant. Das et al., (1998) reported that plant height, branches per plant, pods per plant, pod length and yield per plant had a high genotypic coefficient of variation suggesting the possibility of improvement of greengram by selective breeding.On an average, the higher magnitude of GCV and PCV were recorded for pods per plant, branches per plant, clusters per plant and seed yield suggesting sufficient variability and thus, scope for genetic improvement through selection for these traits.Similar finding was also reported by Neelavati and Govindarasu (2010). The magnitudinal differences were medium to low in GCV and PCV for cluster per plant, harvest index, seed yield per plant and the number of pods per plant suggesting the little role of environment in the expression of these characters. These findings are in agreement with the finding of Das et al., (1998).The studies on GCV and PCV indicated that the presence of a high amount of variation and the role of the environment on the expression of these traits. The magnitude of PCV was higher than GCV for all the characters which may be due to a higher degree of interaction of genotypes with the environment. The differences between PCV and GCV were less to moderate for most of the characters indicating a lesser contribution of environment towards an expression of these characters.
 
Heritability
 
Heritability is a measure of the extent of phenotypic variation caused by the action of genes. For making effective improvement in the character for which selection is practiced, heritability has been adopted by a large number of workers as a reliable indicator.In the present investigation heritability and genetic advance have been worked out for all the thirteen quantitative characters and are presented in Table 3.
       
In a broad sense, high estimates of heritability were recorded for all the characters under study, which ranged from 63.00% (protein content) to 96.00 % (seed yield per plant). High heritability was observed for maximum traits viz., number of clusters per plant (96.00%), number of pods per plant (93.00%), number of seeds per plant (93.00%), plant height (92.00%), pod length (91.00%), seed index (90.00%), days to maturity (89.00%), number of branches per plant (88.00%), harvest index (87.00%), biological yield (81.00%) whereas remaining traits reported moderate to low heritability.High heritability was recorded for the plant height, seed yield per plant, seed index, pods per plant and days to 50%flowering indicating that these traits are likely to be controlled by an additive genetic component. Das et al., (1998) and Loganathan et al., (2001) also reported high heritability for plant height, number of seeds per pod, number of pods per plant and harvest index.
 
Genetic advance as percent of mean
 
The estimate of genetic advance as a percent of mean reported from 6.08 % (protein content) to 65.48 % (number of clusters per plant). High amount of Genetic Advance as 5% of mean was reported for number of clusters per plant (64.48%),seed yield per plant (45.78%), number of pods per plant (44.81%), harvest index (44.42%), seed index (39.61%) whereas moderate for number of branches per plant (37.60%),number of seeds per plant (33.73%), plant height (30.07%), pod length (23.73%), biological yield per plant (23.50%) and low for days to 50% flowering (6.92%),days to maturity (6.26%) and protein content (6.09%). Wani et al., (2007) reported high heritability coupled with high genetic advance for the number of pod per plant, plant height and harvest index suggested the additive genetic control in the inheritance of these characters.High heritability with high genetic advance was recorded for plant height, branches per plant, biological yield per plant and seed yield, suggesting that mostly these traits were under the control of additive gene action and selection will be more useful for yield improvement. Similar results were observed by Jebaraj et al., (2015), Baisakh et al., (2016) and Kumar et al., (2020) for plant height, branches per plant and seed yield in mungbean. Moderate heritability with high genetic advance was found for harvest index, indicating the lesser influence of environment with additive gene action, hence, amenable for selection. High heritability with moderate genetic advance was observed for pods per plant, pod length and seeds per pod, indicating that these traits were less influenced by the environment but governed by both additive and non-additive gene action. Hence,the simple selection method is suggested for the improvement of these traits in the later generations.

The analysis of variance revealed the occurrence of genetic variability among genotypes. In general,the phenotypic coefficient of variation was greater than the genotypic coefficient of variation for all the agro-morphometric traits. High magnitude of GCV and PCV were recorded for clusters per plant, harvest index, seed yield per plant and pods per plant. High heritability coupled with high genetic advance as percent of mean was observed for clusters per plant and seed yield per plant, hence these parameters could be used for selection. Plant height, branches per plant, biological yield, harvest index and seed yield were important traits and should be prioritized while deciding the criteria for selection, which would be useful in yield improvement. It was concluded that in the case of biological yield and seed yield apart from thehigh genotypic coefficient of variation,the estimates of heritability with genetic advance were high,and hence direct mass selection may be rewarded for these two traits.

The authors declare no conflict of interest. This research was conducted as the corresponding author’s Master’s degree program. The authors are thankful to the reviewers for their careful reading of the manuscript and for providing insightful suggestions.

Conceptualization of research; designing of the experiments; execution of field experiments and data collection; analysis of data and interpretation; preparation of the manuscript.