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.