The analysis of variance was done for all the seven characters and their mean square values are mentioned in Table 2. The mean sum of squares due to genotypes showed significant differences for all the studied traits excluding number of seeds per pod and 100-seed weight. Significant differences were reported in five traits (plant height, primary branches per plant, secondary branches per plant, pods per plant, seed yield per plant) indicating the presence of significant genetic variability in the experimental material that can be further utilized for pigeonpea improvement.
Genotypic coefficient of variation
Genotypic coefficient of variation (GCV) was found to be high for seed yield per plant (51.56%) followed by pods per plant (49.01%), primary branches per plant (32.88%) and secondary branches per plant (31.95%). The GCV was moderate for 100-seed weight (13.44%) and low in case of plant height (9.10%) and number of seeds per pod (4.01%) (Table 3). Presence of variability for different traits was also reported by
Rangare et al., (2013); Singh et al., (2014); Ram et al., (2016); Mallesh et al., (2017) and
Reddy and Jayamani, (2019) in cultivated pigeonpea. The expression of variable characters was found to be influenced by environment as genotypic coefficient of variation was reported to be less than respective phenotypic coefficient for all the traits.
Heritability and genetic advance
Pods per plant recorded highest heritability (99.07%) followed by seed yield per plant (97.13%), 100-seed weight (95.64%), secondary branches per plant (94.71%) and primary branches per plant (91.25%). Phenotypic expression can reliably recognize the genotypic character which was concluded from high magnitude of heritability these traits except seeds per pod. Singh
et al. (2019) also reported the high magnitude of heritability for all the traits expect seeds per pod in BC1F3 generation of pigeonpea. Moderate heritability was observed for plant height (48.26%) and low for number of seeds per pod (23.67%).
Genetic advance as % of the mean (GAM) was found to be high (>20%) for all traits, except the plant height (13.03%) and number of seeds per pod (9.11%). The highest genetic advance was recorded (Table 3) for seeds yield per plant (104.67%) followed by number of pods per plant (100.49%), primary branches (64.71%) and secondary branches (64.07%).
Saroj et al., (2013) also reported the higher genetic advance (more than 100%) for yield component traits in pigeonpea. The genetic advance coupled with heritability as % of the mean provides a better explanation of the nature of inheritance and effectiveness of selection for traits of interest
(Johnson et al., 1955).
In the present experiment, the traits
viz., seed yield per plant and pods per plant had higher values of GCV (%), heritability and GAM showing that these traits are under the control of additive gene action and will give response to phenotypic selection. High heritability coupled with moderate genetic advance was observed for 100-seed weight, primary branches per plant and secondary branches per plant. However, plant height had moderate heritability with high genetic advance and number of seeds per pod has lower heritability as well as lower genetic advance. These results depict that phenotypic selection for such traits is not effective as there is predominance of non-additive gene actions.
Correlation and path coefficient analysis
Correlation and path analysis used to estimate the nature and magnitude of association between different characters affecting yield. These analyses help to understand the causes of association which is further exploited in the formulation of selection criteria for yield improvement.
In general, correlation analysis revealed that genotypic correlations were higher than phenotypic correlations and the directions of genotypic and phenotypic correlations were also similar for most of the character combinations. According to Almeida
et al. (2010), demonstrates that genetic factors contributed more than the environmental factor to the correlations, so that genetic correlation were greater than phenotypic correlations. Masking and modifying effects of the environment on association of traits could be the cause of lower phenotypic correlations then genotypic correlations
(Saroj et al., 2013). Correlation coefficients among all the traits are presented in Table 4. Seed yield per plant was found to have highly significant and positive correlation with pods per plant (0.944), plant height (0.398), secondary branches per plant (0.289), 100-seed weight (0.2876) and primary branches per plant (0.2602). However, seeds per pod exhibited positive but non-significant correlation with seed yield per plant.
Pandey et al., (2016), Pushpavalli et al., (2017), Baldaniya et al., (2018) and
Singh et al., (2019) also reported significant and positive correlation between seed yield per plant and number of pods per plant. As it is well known that yield is a complex trait and it depends upon number of yield contributing traits. Selection for specific trait will also bring change in the other related trait. So, the knowledge related to direction and magnitude of association between the components traits is desirable for improvement in the desirable direction.
Correlation analysis depicts the kind of relationship among the traits but does not give information regarding direct or indirect effects. Path coefficient analysis was worked out to understand the extent of relationship by considering seed yield per plant as dependent variable and rest of the traits are considered as independent variables. Results of path coefficient analysis with direct and indirect effects are mentioned in Table 5. Highest positive direct effect on seed yield per plant was exhibited by number of pods per plant (0.48) followed by 100-seed weight (0.25), seeds per pod (0.18) and secondary branches per plant (0.13). Pods per plant also exhibited positive indirect effect on seed yield per plant via secondary branches and 100-seed weight. Present results clearly indicated that selecting for high yield focus should be given on number of pods per plant, secondary branches per plant and 100-seed weight which shows high direct positive effect along with positive correlation. Negative direct effect on seed yield per plant was shown by primary branches per plant. The association of pods per plant, secondary branches per plant, plant height and 100-seed weight with seed yield per plant was positive due to positive direct effects. Similar outcomes were also reported by
Kothimbire et al., (2016), Ram et al., (2016), Kumar et al., (2017), Ranjani et al., (2018) and
Singh et al., (2019). Above results indicated that indirect selection for higher seed yield can be achieved through secondary branches per plant.