Genetic divergence and character association studies in chickpea (Cicer arietinum L.) genotypes for seed yield and its component traits

Introduction

Pulses, the edible dry seeds of Leguminosae plants, are valued for their high protein, dietary fiber, mineral content, and low fat and cholesterol levels, making them important for nutritional security and management of metabolic disorders (Rawal and Navarro, 2019). Among pulses, chickpea (Cicer arietinum L.) is one of the most widely cultivated coolseason grain legumes and is commonly known as the "King of Pulses." It is a self-pollinated diploid species (2n=14) belonging to the family Fabaceae and is believed to have originated in southeastern Turkey from its wild progenitor Cicer reticulatum (Helbaek, 1970; Georgina Pearman, 2005). Two major cultivated types, desi and kabuli, differ mainly in seed size, colour, and geographical distribution (Moreno and Cubero, 1978). Chickpea seeds contain about 21-24% protein, 62% carbohydrates, and essential minerals such as calcium, phosphorus, and iron, making them an economical source of plant-based nutrition (Ali et al., 2011). The crop also improves soil fertility through symbiotic nitrogen fixation by Rhizobium spp. India contributes nearly 77% of the world's chickpea area and production. During 2023-24, chickpea occupied 10.91 million hectares with a production of 13.75 million tonnes and productivity of 1260 kg ha⁻¹ (Anonymous, 2022) [15,4,14,11,1,2] . Genetic variability and heritability studies are crucial for chickpea improvement, particularly for yield-related traits such as pods per plant, branches, and harvest index (Kumar et al., 2012; Malik et al., 2014). Therefore, evaluation of diverse germplasm is essential for identifying superior genotypes for future breeding programmes [23] .

Materials and Methods

The experimental material, comprising thirty-four diverse chickpea genotypes along with four standard checks, was evaluated using a Randomized Block Design (RBD) with three replications. Each genotype was sown in a plot measuring 4.0 m × 1.50 m, consisting of five rows of 4 m length. A spacing of 40 cm between rows and 10 cm between plants was maintained. All recommended agronomic practices were uniformly followed to ensure the establishment of a healthy and optimal crop stand. Observations on various quantitative traits under study were recorded from five randomly selected competitive plants per genotype in each replication. However, days to 50% flowering and days to maturity were recorded on a wholeplot basis.

Result and Discussion

Analysis of variance

The analysis of variance revealed that mean squares due to genotypes were highly significant for all the traits studied, including yield and its component characters in chickpea (Table 1). Significant differences among genotypes were observed for days to 50% flowering, days to maturity, plant height (cm), number of primary branches per plant, number of secondary branches per plant, number of pods per plant, 100-seed weight (g), biological yield per plant (g), seed yield per plant (g), harvest index (%), and protein content (%). These findings are in agreement with earlier reports by Jakhar et al. (2016) and Bhanu et al. (2017), who also observed significant variation among chickpea genotypes for the traits under study. The presence of substantial variability among genotypes indicates ample scope for improvement through selection and hybridization [5,3] .

Genetic Variability parameters estimate

The analysis of genetic variability among 34 chickpea genotypes (Table 2) revealed considerable variation for most of the studied traits, indicating good scope for selection and crop improvement. Among all characters, seed yield per plant (SYPP) recorded the highest genotypic coefficient of variation (GCV = 22.68%) and phenotypic coefficient of variation (PCV = 23.09%), followed by hundred seed weight (HSW) with GCV and PCV values of 20.77% and 21.56%, respectively. This suggests the presence of substantial variability for these economically important traits. Primary branches per plant also exhibited relatively high variability with GCV of 18 [8,10,17,13,22,12] .

Correlation coefficient estimates for seed yield and its component traits

The genotypic (rg) and phenotypic (rp) correlation analysis revealed important associations among yield and yield contributing traits in chickpea. In most cases, genotypic correlations were higher than phenotypic correlations, indicating strong genetic control over these characters (Table 3). Seed yield per plant (SYPP) showed strong positive association with important traits such as plant height (PHT) (rg = 0.73**, rp = 0.66**), biological yield per plant (BYPP) (rg = 0.43**, rp = 0.34**) and harvest index (HI) (rg = 0.51**, rp = 0.43**). This indicates that these traits contributed directly towards higher seed yield and may be useful selection criteria in breeding programmes. [6,19,7] .

Overall, the study suggested that plant height, biological yield per plant, harvest index and pods per plant were the major yield contributing traits and should be given importance during selection for yield improvement in chickpea.

PC-Protein Content

Genetic divergence and clustering of similar genotypes

The genetic divergence analysis using Mahalanobis D² statistics revealed considerable diversity among the chickpea genotypes, indicating good scope for selection of diverse parents in breeding programmes. Based on Tocher's clustering method, the 34 genotypes were grouped into twelve clusters. Cluster I contained the maximum number of genotypes (19), showing the presence of considerable similarity among most of the entries, whereas clusters V to XII were monogenotypic, indicating high uniqueness of those genotypes. The cluster mean analysis showed wide variation for different yield and yield contributing traits ( The intra-and inter-cluster distance analysis indicated substantial genetic divergence among clusters. The maximum inter-cluster distance was observed between Cluster X and Cluster V (15.99), followed by Cluster XII and Cluster X (15.59), suggesting that genotypes belonging to these clusters are highly diverse and may be utilized for hybridization to obtain better recombinants and heterotic combinations (Table 6). On the other hand, the minimum inter-cluster distance was observed between Cluster VI and Cluster V (6.34), indicating close genetic similarity among genotypes of these clusters. Among the different traits, plant height contributed the maximum towards total genetic divergence (34.69%), followed by harvest index (16.67%) and number of pods per plant (10.86%). In contrast, primary branches per plant contributed the least (1.00%). The results indicated that traits like plant height, harvest index and pods per plant played a major role in creating genetic variability among the chickpea genotypes and may be considered important during parent selection in chickpea improvement programmes (Table 5). These findings are in agreement with earlier reports by [21,18,16,20] .

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