The success of selection in any crop improvement program depends not only on the variability present in yield but also on the interrelationships among these traits within the population.
Mean performance of cowpea genotypes
Legume breeders globally have been utilizing the accessible genetic resources to develop varieties. In cowpea breeding programs, certain yield attributing traits should be prioritized. Therefore, cowpea germplasm must be thoroughly evaluated for these traits to identify suitable accessions for breeding programs. Thus, in the present investigation, different promising varieties were evaluated under Haryana weather conditions and significant variation was noticed among the cowpea genotypes for yieldattributes indicating considerable genetic diversity for improvement
(Kandel et al., 2019).The mean performance of these varieties is depicted in Table 1 and further discussed below:
Variability in vegetative characters including plant height and number of branches among cowpea genotypes has been frequently reported and is largely attributed to genetic makeup and growth habit differences
(Singh et al., 2018). Plant height varied significantly among the studied genotypes and ranged from 43.18 to 95.24 cm. Arka Garima (95.24 cm) recorded the maximum plant height and was significantly superior to all other genotypes. Number of branches per plant ranged from 4.88 to 8.02. Arka Garima recorded the highest number of branches (8.02), followed by C-152 (7.52) and Kashi Gauri (7.21), while Kashi Nidhi (4.88) recorded the lowest number of branches. More branching contributes to better canopy architecture and may indirectly improve pod-bearing sites. Similar genotypic variations for branching in cowpea have been reported by
Pawar et al., (2016).
Days to 50% flowering showed significant variation and ranged from 48.10 to 62.11 days. Kashi Kanchan was the earliest to flower (48.10 days), followed by Cowpea-263 (49.70 days). Early flowering accessions are often given preference as they escape terminal drought and certify improved yield stability. Negative associations between delayed flowering and yield have also been noticed in cowpea earlier (
Nalawade, 2021).
Variability in seed yield and yield attributing characters including number of pod, number of seeds, pod length and pod weight among cowpea genotypes has been frequently reported. Number of pods per plant varied significantly among the genotypes and ranged from 8.35 to 14.96. Kashi Kanchan recorded the highest number of pods per plant (14.96), which was statistically at par with Cowpea-263 (14.73) followed by Arka Garima (14.10). Number of pods per plant is a chief yield-determining trait in cowpea and similar results have been noticed earlier in legume
(Massey et al., 2020).Number of seeds per pod ranged from 6.15 to 10.57. Kashi Nidhi (10.57) recorded the maximum number of seeds per pod, which was statistically at par with Kashi Kanchan (10.25) and Kashi Shyamal (10.32). Genotypic variations in number of seeds per pod highlight differences in reproductive abilities and assimilate translocation and partitioning, as also observed by
Vaggar et al., (2022). Seed yield per plant exhibited wide variation, ranging from 6.78 to 16.32 g. Cowpea-263 (16.32 g) recorded the highest seed yield per plant and was statistically at par with Kashi Kanchan (16.14 g).High seed yield in Cowpea-263 and Kashi Kanchan can be attributed to their higher pod number, pod weight and test weight.
Singh et al., (2018) and
Reddy et al., (2016) also observed similar trends in high-yielding cowpea genotypes.
Pod weight ranged from 5.24 to 8.73 g. Kashi Kanchan recorded significantly higher pod weight (8.73 g) and was statistically at par with Cowpea-263 (8.55 g), followed by Kashi Nidhi (8.15). Higher pod weight directly contributes to increased pod and seed yield and is an important yield component trait.Pod length varied from 11.56 to 19.07 cm. Kashi Kanchan recorded the longest pods (19.07 cm), followed by Cowpea-263 (18.05 cm) and Kashi Gauri (17.76 cm).
Kavyashree et al., (2023) and
Jonah et al., (2021) also observed that longer pods usually accommodate more seeds, thus increasing yield potential of genotypes.Pod yield per plant ranged from 41.25 to 127.84 g. Kashi Kanchan (127.84 g) recorded the highest pod yield per plant and was significantly superior to all other genotypes except Cowpea-263 (122.87 g). Higher pod number, pod length and pod weight in Kashi Kanchan and Cowpea-263 can be attributed to their higher pod yield.
Test weight ranged from 7.02 to 9.95 g. Cowpea-263 (9.95 g) recorded the highest test weight was statistically at par with Kashi Kanchan (9.58 g) followed by Kashi Gauri (9.38 g). Higher test weight is positively correlated with seed yield and confirms the presence of bold seeds as observed earlier in cowpea and other legumes
(Mali et al., 2021).
In general, the results reflected that Kashi Kanchan and Cowpea-263 constantly performed better for majority of the studied growth and yield characters.In agreement with earlier findings of
Aliyu et al., (2019), the reported variability among accessions provides a strong genetic base for selection and development of high-yielding cowpea cultivars.
Correlation analysis among yield and yield attributing traits
Correlation analysis was carried out to elucidate the nature and magnitude of associations among yield and its contributing traits in cowpea. The correlation coefficients mentioned in Table 2 and depicted in shaded phenotypic correlogram (Fig 1) revealed a complex interrelationship among growth, phenological and yield attributes.
Number of pods per plant exhibited strong and significant positive correlations with pod length (r = 0.791), number of seeds per pod (r = 0.762), pod weight (r = 0.861), test weight (r = 0.815), seed yield per plant (r = 0.812) and pod yield per plant (r = 0.849). This noticeably reflect that number of pods per plant is a key yield-governing trait in cowpea, as increased pod bearing ability directly improve both seed and pod yield. An increase in pod number directly enhances sink strength, leading to higher seed and pod yield
(Nagalakshmi et al., 2020).
Pod length showed highly significant positive correlations with number of seeds per pod (r = 0.787), pod weight (r = 0.827), test weight (r = 0.846), seed yield per plant (r = 0.866) and pod yield per plant (r = 0.871). These associations propose that longer pods be inclined to accommodate more seeds, thus increasing pod mass and ultimately contributing to higher seed and pod yield. The strong positive association between pod length and yield components emphasizing its function as an integrative trait governing both seed size and seed number (
Lokesh and Murthy, 2017).
Correlation analysis among yield and yield attributing traits
Correlation analysis was carried out to elucidate the nature and magnitude of associations among yield and its contributing traits in cowpea. The correlation coefficients mentioned in Table 2 and depicted in shaded phenotypic correlogram (Fig 1) revealed a complex interrelationship among growth, phenological and yield attributes.
Number of pods per plant exhibited strong and significant positive correlations with pod length (r = 0.791), number of seeds per pod (r = 0.762), pod weight (r = 0.861), test weight (r = 0.815), seed yield per plant (r = 0.812) and pod yield per plant (r = 0.849). This noticeably reflect that number of pods per plant is a key yield-governing trait in cowpea, as increased pod bearing ability directly improve both seed and pod yield. An increase in pod number directly enhances sink strength, leading to higher seed and pod yield
(Nagalakshmi et al., 2020).
Pod length showed highly significant positive correlations with number of seeds per pod (r = 0.787), pod weight (r = 0.827), test weight (r = 0.846), seed yield per plant (r = 0.866) and pod yield per plant (r = 0.871). These associations propose that longer pods be inclined to accommodate more seeds, thus increasing pod mass and ultimately contributing to higher seed and pod yield.The strong positive association between pod length and yield components emphasizing its function as an integrative trait governing both seed size and seed number (
Lokesh and Murthy, 2017).
Number of seeds per pod was also positively and significantly correlated with pod weight (r = 0.791), test weight (r = 0.779), seed yield per plant (r = 0.813) and pod yield per plant (r = 0.793). This depicts that genotypes with more seeds per pod tend to show superior yield performance, probable due to better assimilate translocation and partitioning towards reproductive sinks
(Nimbal et al., 2024).
Pod weight showed one of the strongest associations with seed yield per plant (r = 0.860) and pod yield per plant (r = 0.885), reflecting its direct involvement to yield improvement. The strong positive correlation between pod weight and test weight (r = 0.788) further recommends that heavier pods are mostly coupled with bolder seeds, which positively affect final yield.
Test weight also confirmed strong positive correlations with seed yield per plant (r = 0.840) and pod yield per plant (r = 0.820), demonstrating that seed size and density play a significant role in determine seed yield. This result supports the idea that selection for higher test weight can efficiently improve overall productivity
(Nkoana et al., 2019).
Days to 50% flowering showed negative correlations with most yield-related traits, including pod weight (r = -0.358), seed yield per plant (r = -0.302) and pod yield per plant (r = -0.327). These negative associations demonstrate that early-flowering genotypes tend to produce higher yields, probably due to a longer effective reproductive period and better exploitation of accessible resources
(Sharma et al., 2016).
Number of branches per plant exhibited weak to moderate positive correlations with number of pods per plant (r = 0.345) and days to 50% flowering (r = 0.561), but its interaction with seed yield (r = 0.152) and pod yield (r = 0.171) was relatively weak. This suggests that although branching contributes to plant architecture but its direct effect on seed and pod yield is low compared to reproductive traits.
Overall, the correlation matrix clearly indicates that number of pods per plant, pod length, number of seeds per pod, pod weight and test weight are the most significant characters contributing towards seed and pod yield in cowpea. The strong positive association among these traits suggests that synchronized yield improvement is feasible through indirect selection
(Pushkar et al., 2018).
Principal component analysis (PCA)
PCA was used to analyze the size and structure of variability across cowpea genotypes for seed yield and yield attributing parameters, as well as to elucidate interrelationships between them. The PCA results form a strong multivariate framework for analyzing yield variation and identifying essential traits and superior genotypes
(Suganthi et al., 2007). The analysis of Eigen value demonstrated that the first three principal components collectively explained 96.17% of the total variation (Table 3). Such presence of variability within the first few components has been widely reported in multivariate studies on yield traits of legumes (
Abdi and Williams, 2010).
The first principal component (PC1) accounted for 61.01% of the total variance and was predominantly associated with major yield-contributing traits such as number of pods per plant, pod length, pod weight, test weight, seed yield per plant and pod yield per plant. The strong positive loadings of these reproductive traits along PC1 indicate that they collectively constitute the principal yield axis in cowpea and play a decisive role in determining productivity. The second principal component (PC2) contributed 25.18% of the total variation and was mainly associated with phenological and architectural traits including days to 50% flowering and number of branches per plant. The near-perpendicular orientation of these traits relative to the yield components in the biplot suggests a comparatively weaker association between vegetative growth traits and direct yield expression
(Reddy et al., 2025).
Genotypic distribution in the PCA biplot (Fig 2) further highlighted clear differentiation among accessions. High-yielding genotypes such as Kashi Kanchan and Cowpea-263 were positioned on the positive side of PC1 and clustered close to key yield attributes, reflecting their superior expression of reproductive traits. In contrast, genotypes Konkan Safed and Konkan Sadabhar located on the negative side of PC1 exhibited weaker association with yield components and comparatively lower productivity. However, Pusa Komal, Kashi Nidhi and Kashi Shyamal were located at an intermediate position but remained distant from the primary yield cluster, indicating average performance
(Reddy et al., 2021).
Overall, the PCA results demonstrate that yield variability in cowpea is primarily governed by reproductive traits related to pod development and seed size. From a breeding perspective, genotypes positioned near the positive PC1 axis represent promising genetic resources, while traits with high positive loadings on this component may serve as reliable selection criteria for developing high-yielding cowpea cultivars (
Girgel, 2021).