Estimates of genetic variability, divergence, correlation and path coefficient for morphological traits in fenugreek (Trigonella foenum-graecum L.) genotypes

Fenugreek (Trigonella foenum-graecum L.) is a seed spices crop, diploid species with chromosome number of 2n=16. The genus Trigonella is one of the largest genera of the tribe Trifoliate in the family Fabaceae and sub-family Papilionaceae (Balodi and Rao, 1991). Studies on variability, character associations for different agronomic characters in fenugreek have been made by Singh and Raghuvanshi, (1984) and Saha and Kale, (2001).  
 
The degree of association among such variables can be determined through correlation analysis. The ultimate expression of yield in crop plants is usually dependent upon the action and interaction of a number of important characters (Elias, 1992). Genotypic correlation coefficients provide a measure of genetic association between traits in order to identify the important traits (Pandey and Gritton, 1975). Phenotypic correlations do not always indicate genetic causation but may in fact be due to the underlying population structure (Kempthorne, 1957). Nonetheless, phenotypic correlations are suitable for describing populations but caution is required if implying causation, particularly beyond the test population (Loomis and Connor, 1992).

The present study was carried out to assess the variability and character association in 17 genotypes of fenugreek. The genotypes under study were grown in RBD with 3 replications at ICAR-NRCSS, Ajmer (Rajasthan) during rabi of 2014-15 and 2015-16. Analysis of variance was done by the method suggested by Panse and Sukhatme (1985). Mean data from each of the replications were used to estimate phenotypic and genotypic coefficients of variations as per Burton (1952); heritability (broad sense) and genetic advance were determine by following the methodology of Johnson et al., (1955). The phenotypic and genotypic correlation coefficients were calculated as per the methods given by Al-Jibouri et al., (1958). The path coefficients were obtained by following the method of Dewey and Lu (1959) and data analysis was done with the help of Windostate software. Same germplasm lines were used to identify the genetic diversity among the used germplasm lines and dendrogram (Fig1) was generated using NTSYS-PC 2.02j (Rohlf, 1998) software.
 

The mean performance of fenugreek genotypes was very high for all characters (Table 1). The analysis of variance was estimated and found significant for all characters except primary branches and secondary branches (Table 2). Plant height, number of pods per plant, number of seeds per pod, test weight, 5 plants seed yield and seed yield per plot had wide variability (Table 3). The difference between the value of PCV and GCV was narrow for number of primary branches, number of secondary branches, and number of seeds per pod. Characters like plant height and 5 plants seed yield were found to be consistent in its behaviour at both phenotypic and genotypic levels. It suggested that these traits were least influenced by the non genetic factors, hence quite stable. This is accordance with finding of Banerjee and Kole (2004) and Naik (2012). The estimates of phenotypic and genotypic coefficients of variation were high for seed yield per plot followed by test weight and 5 plants’ seed yield. Moderate PCV and GCV were observed for number of seeds per pod. The differences between PCV and GCV were maximum with respect to number of pod per plant, number of seeds per pod, test weight and seed yield per plot. These results are in agreement with the earlier findings for number of pods per plant reported by Pant et al., 1984 and Chandra et al., 2000.
 

 

 

 
Genetic advance
 
The genetic advance is more useful than heritability alone in predicting the resultant effect on selecting best individuals. In the present investigation, expected genetic advance was recorded maximum with seed yield per plot followed by 5 plants seed yield and plant height. This is accordance with finding of Prajapati et al., (2010) and Naik (2012). In the present investigation, expected genetic advance expressed as percentage of mean was high for seed yield per plot followed by test weight, 5 plants seed yield, number of seeds per pod, number of primary branches, plant height and number of secondary branches (Table 3).
 
Genetic divergence
 
The multivariate analysis based on D² values among 17genotypes revealed that all genotypes can be grouped into six clusters. Among these, cluster-I consisted of 12 genotypes and remaining all clusters (II, III IV, V, VI) were monogenotypic (Table 4).
 

 
Cluster I showed maximum intra-cluster distance. Intra-cluster distance is the main criterion for selection of genotypes using D² analysis. Inter-cluster distance varied from 3.63 to 10.69. Minimum inter-cluster D² value was observed between clusters II and IV (3.63) indicating the close relationship among the genotypes included in these clusters (Table 5). Maximum inter-cluster value was observed between clusters IV and VI (10.69) indicating maximum divergence between the genotypes of these clusters. The inter-cluster D² value were also higher between the clusters III and VI (10.56), clusters IV and V (9.34), clusters III and V (9.28) and clusters II and VI (8.38). The contribution of various characters to divergence in fenugreek was recordedand found that 46.3 per cent contribution for five plants seed yield (Table 6) followed by number primary branches (16.9%). The cluster mean value of all characters in fenugreek germplasm shown in Table 7 indicated that all characters found wide variability.
 

 

 

 
Genotypic and phenotypic correlation coefficient
 
The phenotypic and genotypic correlation among the yield and yield components in fenugreek are presented in Table  8. In the present investigation, 5 plants seed yield was positively and significantly correlated with number of pod per plant, number of seeds per pod and seed yield per plot at both genotypic and phenotypic level. Therefore, these characters should be considered while making selection for yield improvement in fenugreek. These results are in accordance with the results of Ananya and Kole (2004) for biological yield per plant and harvest index. On the other hand, number of pod per plant showed positive and significant correlation with number of seeds per pod and seed yield per plot at both genotypic and phenotypic level (Table 8). Plant height was negatively and non-significantly correlated with number of primary branches, number of secondary branches and test weight. Similar findings have been reported by Singh et al., (2006) and Sarada et al., (2008).
 

 
Path coefficient analysis
 
Genotypic path analysis of the different characters revealed that seed yield per plot had highest positive direct effect on 5 plants seed yield followed by number of pod per plant, plant height, number of secondary branches and test weight (Table 9). The several studies have shown importance by various scientists reported by Singh et al., (2006) and Fikreselassie et al., (2012).
 

The highest GCV and PCV were observed for seed yield per plot followed by test weight and 5 plants seed yield that showed these trait not influenced by the environment. The highest genetic advance was observed for seed yield per plot followed by 5 plants seed yield and plant height. The highest heritability was estimated for 5 plants seed yield followed by plant height and number of primary branches this indicated that these characters is high heritable and selection can only made for these traits. The genotypes were grouped into six clusters. These cluster is wide variable each other.It was concluded that improvement of seed yield in fenugreek can possible through selection for number of pod per plant, number of seeds per pod, plant height and number of primary branches.