Analysis of variability parameters
Analysis of variance for various characters is presented in Table 1. Analysis revealed significant progeny mean square values for all the traits in F4 progenies. It showed the sufficient variability in material under study. Similar results were reported by
Patel et al., (2016) and
Hadavani et al., (2018).
In the present study, the result of measures of variability parameters is presented in Table 2 and Graph 1. Mean values revealed vast range for days to 50% flowering (51-59), days to maturity (93-97), plant height (26.23-63.58 cm), racemes per plant (2.61-7.87), pods per raceme (3.01-7.24), pods per plant (9.39-39.40), pod length (4.85-8.01 cm), pod width (0.71-2.09 cm), pod weight (0.41-0.97 g), seeds per pod (2.90-3.86) and seed yield per plant (4.62-13.19 g). Based on the mean values, the progeny D32-10-2 (13.19 g) recorded significantly higher seed yield per plant over check varieties GNIB 21 and GNIB 22. Higher values of GCV and PCVwere observed for pods per raceme (21.69% and 25.73% respectively), pods per plant (36.44% and 39.77% respectively) and seed yield per plant (22.32% and 26.06% respectively) and the less differences between GCV and PCV for these traits revealed less influences of environment on these traits so that there is great scope of improvement by applying selection on these characters. Similar results were reported for pods per plant and seed yield per plant by
Choudhary et al. (2016). For pods per plant by
Chaitanya et al. (2014) and
Jyothireddy et al. (2018).
High heritability (broad sense) values of more than 60 per cent was observed for racemes per plant (69.13%), pods per raceme (71.07%), pods per plant (83.97%), pod length (76.23%), pod width (85.89%) and seed yield per plant (73.35%) indicating that the traits are generally governed by additive gene effects and improvement for these traits could be made by simple phenotypic selection. Similar outcomes were reported for racemes per plant and pods per plant by
Pawar and Prajapati (2013); for racemes per plant and seed yield per plant by
Asaduzzaman et al. (2015); for pod length, pod width, pods per plant and seed yield per plant by
Hadavani et al. (2018).
High genetic advance as per cent mean was observed for plant height (24.43%), racemes per plant (33.60%), pods per raceme (37.67%), pods per plant (68.78%), pod width (37.23%), pod weight (27.69%) and seed yield per plant (39.38%). Similar results were observed for pod width and seed yield per plant by
Hadavani et al. (2018); for plant height and pods per plant by
Chaitanya et al., (2014); for pods per plant by
Patel et al. (2016).
Heritability with genetic advance collectively, giving more detailed idea of gene action. High heritability coupled with high genetic advance as per cent of mean were perceived for racemes per plant (69.13% and 33.60% respectively), pods per raceme (71.07% and 37.67% respectively), pods per plant (83.97% and 68.78% respectively), pod width (85.89% and 37.23% respectively) and seed yield per plant (73.35% and 39.38% respectively) showing role of additive gene effects and less influence of environmental factors on the expression of these traits. Thus, improvement of these characters could be achieved through direct phenotypic selection. These results are in accordance withthe earlier finding of
Choudhary et al. (2016) and
Hadavani et al. (2018) for Pod per plant, pod width and seed yield per plant.
Correlation coefficient analysis
The association studies among 11 charecters (Table 3) revealed that, seed yield per plant appeared highly significant and positively correlated at genotypic level with days to maturity (0.419), plant height (0.348), racemes per plant (0.790), pods per raceme (0.743), pods per plant (0.829) and seeds per pod (0.480), which suggested, such component characters can be improved simultaneously with seed yield per plant by direct selection. Similar results were obtained for correlation of seed yield per plant with days to maturity and pods per plant by
Kamble et al. (2015); with pods per plant by
Salim et al., (2013). It also exhibited negative and non-significant correlation with pod width (-0.076). Whereas, seed yield was observed to be non-significantly associated with days to 50% flowering (0.040), pod length (0.123) and pod weight (0.048), indicated less significance of these traits from improvement point of view.
Plant height had significant positive correlation with days to 50% flowering (0.294) and days to maturity (0.353) and seed yield per plant (0.348). But, early flowering and early maturity is desirable in Indian bean. Therefore, for increasing seed yield potential, optimum plant height should be considered while selections for higher seed yield. The traits racemes per plant, pods per raceme and pods per plants were significantly and positively associated with each other, similarly, pod length, pod width, pod weight and seeds per pod were significantly and positively associated with each other suggesting such traits can be improved indirectly through direct selections for increasing seed yield.
Path coefficient analysis
The direct and indirect effects of various yield component traits on seed yield per plant are given in Table 4. The overall path analysis revealed that high positive direct effects on seed yield per plant was registered by pod per raceme (7.995) followed by racemes per plant (6.795), pod length (4.158), days to 50% flowering (2.557), plant height (1.250), pod weight (0.244) and days to maturity (0.080). Therefore, selection for such traits would bring about improvement in Indian bean. The results are in accordance with
Pawar and Prajapati (2013) for racemes per plant and days to 50% flowering,
Kamble et al. (2015) for pod length, plant height and days to maturity,
Dewangan et al. (2018) for pods per raceme, pod length and pod weight. The highest negative direct effects on seed yield per plant was recorded by pods per plant (-12.863) followed by seeds per pod (-3.221) and pod width (-1.098) suggesting less significance of these traits during selections for higher seed yield. Pods per plant and seeds per plant showed high negative direct effects, although they rendered highly significant correlation with seed yield per plant, which might be due to positive indirect effects via other casual traits. Such traits with direct and indirect effects of varying magnitude and opposite in the direction, counterbalancing each other will not be more useful in breeding programme. In general, it was observed that all the character recorded high to very high magnitude of indirect effects on seed yield per plant via racemes per plant, pods per raceme, pods per plant and pod length. Path analysis for seed yield revealed high residual effect of 0.85, which implies that more other traits need to be included in future studies to increase per cent accountable variation in the investigations.