The analysis of variance indicated significant differences among the genotypes for all the traits studied. The estimates of PCV were higher than corresponding GCV (Table 2) though differences were relatively low for all the traits studied. This indicated highly heritable and comparatively stable nature of the characters and thus, the selection based on phenotypic performance would be quite effective in the improvement of these traits
(Sekhon et al., 2019). The magnitude of PCV and GCV was high for pod yield/plant (Table 2) ensuring ample scope for improvement through selection. Besides, number of primary branches/plant, internodal length, harvest duration and pods/plant also showed high PCV but moderate estimates of GCV. The differences in the magnitude of PCV and GCV indicated that environment had definitely played a role in their manifestations.
Sharma et al., (2003), Sharma et al., (2009), Katoch et al., (2016) and
Sekhon et al., (2019) have also reported high PCV and GCV for pod yield/plant in different studies involving different sets of genotypes in garden pea. In contrary,
Sharma et al., (2007) and
Saxesena et al., (2014) also noticed moderate PCV and GCV for pod yield/ plant which could be due to variation in genetic material and environmental conditions. The moderate estimates of PCV and GCV were recorded for plant height, pod breadth, average pod weight, ascorbic acid and total sugars. In addition, pod length, seeds/pod, total soluble solids (whole pod) and protein content was also revealed moderate estimates of PCV but magnitude of GCV was low suggesting cautious approach while following direct selection for these traits.
The magnitude of heritability indicates the reliability with which a genotype can be recognized by its phenotypic expression. However, high heritability alone is not enough to make sufficient improvement through selection generally in advance generations unless accompanied by substantial amount of genetic advance (
Sharma and Kalia 2002). Hence, high genetic advance coupled with high heritability offers the most effective selection criteria for selection
(Karimizadeh et al., 2011) and was observed for internodal length, plant height, average pod weight and pod yield per plant. The inheritance of these characters indicated the importance of additive gene action and possibility of selection in the early generations
(Katoch et al., 2016). High heritability along with moderate genetic advance was observed for days to flowering, pod length, pod breadth, pods per plant and total sugars which indicated the preponderance of additive and non-additive gene effects for their inheritance
(Saxesena et al., 2014), suggesting that improvement in these traits can be achieved by following hybridization and selections in the later generations.
Yield is a complex polygenic trait that results from multiple interactions between component traits. Selection for yield may not be effective unless other yield components influencing it directly or indirectly are taken into consideration. The correlation studies helps in simultaneous selection of traits of interest influencing yield (
Semahegn and Tesfaye 2016). Therefore, identification of key traits is important which contribute effectively for enhancing yield (
Jain et al., 2015) and defining an ideal plant type. In general, the genotypic correlation coefficients were higher in magnitude than the corresponding phenotypic ones (Table 3) which revealed that though there is a strong inherent association between various characters, the phenotypic expression of the correlation gets reduced under the influence of environment. The effective yield improvement would be achieved through the characters which have significant and positive/desirable correlation with each other. Genotypic correlation provides measures of genetic association between characters and is more reliable than phenotypic correlation and thus, helps to identify the characters to be utilized while doing selection in breeding programmes.
Pod yield per plant had shown a positive and significant correlation at both phenotypic and genotypic levels with pod length, pod breadth, pods per plant, average pod weight and total sugars. Precedent studies of many research workers have also indicated significant and positive association of these traits with yield per plant (
Sharma and Kalia 1998;
Sharma et al., 2007; Sharma et al., 2009; Katoch et al., 2016). Inter-relationship among different growth parameters revealed that first flower node, days to flowering, days to first picking, and nodes per plant had significant and positive association among themselves. Among the pod characters positive association of pod length was recorded with pod breadth, seeds per pod and average pod weight along with negative correlation with total soluble solids (whole pod) at both genotypic and phenotypic levels.
Srivastava and Singh (1989) have also reported positive association of pod length with seeds per pod while
Kalloo et al., (2005) observed the same with average pod weight. Seeds per pod also showed positive association with average pod weight at both the levels along with moisture content and total soluble solids (whole pod) at genotypic level only. On the other hand, pods per plant indicated negative association with total soluble solids (seed) at both the levels along with protein content at genotypic level only. Besides, a positive association between pods per plant and total sugars at genotypic level was also observed.
Correlation coefficients alone are insufficient to recognize cause and effect relationships among traits associated with yield. Path coefficient analysis permits a better understanding of associations between different characters by dividing the magnitude of association with the dependent character into direct and indirect effects (
Ukaoma et al., 2013) thus, helps in formulating an effective selection programme. Pods per plant and average pod weight at both genotypic and phenotypic levels revealed maximum positive direct effects on fresh pod yield per plant suggesting the importance of these traits towards fresh pod yield (Table 4). Besides, days to flowering followed by nodes per plant, pod length, total soluble solids (pod) and total sugars had also substantial positive contribution as direct effects towards pod yield at genotypic level. A critical examine of path coefficients revealed that pods per plant and average pod weight, in general, contributed maximum
via their indirect effect to the total association of majority of traits with pod yield.