Genetic variability and heritability of yield-related traits in sweet corn genotypes

Introduction

Sweet corn (Zea mays L. var. saccharata) is an important vegetable and specialty type of maize valued for its tender kernels, sweetness, palatability and nutritional quality. Its kernels contain higher levels of sugars during the milk to early dough stage, with sucrose being the predominant sugar (Oktem and Oktem., 2005; Hale et al., 2005) [4,8] . Thus, both yield and kernel quality are important targets in sweet corn improvement. The success of a breeding programme depends largely on the magnitude and nature of genetic variability available in the breeding material. Genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance as a percentage of mean (GAM) are useful parameters for assessing variability and predicting the potential response to selection (Burton, 1953; Johnson et al., 1955) [3,10] . Evaluation of these parameters for yield components and quality traits can help identify characters with greater selection potential. Although genetic variability and heritability for yield and quality traits have been reported in sweet corn, information on the simultaneous selection potential of yield components and sweetness-related traits in specific germplasm under local growing conditions remains limited (Dagla et al., 2015; Niji et al., 2018; Rajasekar et al., 2024) [4,13,15] . Identification of genotypes combining high cob yield with desirable quality attributes is therefore important for sweet corn improvement. Hence, the present study was undertaken to assess genetic variability, heritability and expected genetic advance for yield and quality traits among sweet corn genotypes and to identify promising genotypes and traits for selection in future breeding programmes.

Materials and Methods

The field experiment was conducted during the Kharif season of 2025 at the R.K. Nagar Farm of the All India Coordinated Research Project (AICRP) on Maize, located at Kolhapur (Shenda Park farm). The experimental location features redcoloured soil characterized by effective drainage and high moisture retention capacity suitable for sweet corn cultivation. The experimental material comprised 20 coded sweet corn genotypes (including 17 test genotypes and three checks) obtained from the AICRP on Maize Improvement Project at Kasba Bawada, Kolhapur which are given in Table No. 1. The trial was laid out in a Randomized Block Design (RBD) with three replications. Each entry in each replication was sown with the plot size of 4.00 x 1.20 m with a spacing of 60 cm between rows and 20 cm between plants. A standard fertilizer dose of 120:60:40 kg/ha of N, P 2 O 5 and K 2 O was adopted, applying a basal dose of 60:60:40 kg/ha alongside a split application of the remaining 60 kg N at 45 days after sowing. Observations were recorded from five randomly selected plants tagged at 35 days after sowing within each treatment and replication and average values per plant were computed. Important quantitative traits were evaluated: days to 50% tasseling, days to 50% silking, plant count at harvest, number of cobs per plot at harvest, mean cob length with husk (cm), mean cob length without husk (cm), mean cob girth with husk (cm), mean cob girth without husk (cm), number of kernel rows per cob, number of kernels per row, plant height (cm), cob height (cm), 100-kernel weight (g) and cob yield per plant with husk (g). In addition, three biochemical characteristics were analyzed: Reducing sugar (%) using the Fehling's reagent titration method with methylene blue indicator, Sucrose content (%) derived by subtracting reducing sugars from total sugars estimated and Brix (%) measured via a refractometer at milk stage. Statistical analysis of the mean values was carried out by subjecting the data to Analysis of Variance (ANOVA) as per Gomez and Gomez (1984). Genotypic, phenotypic and environmental variances were calculated as per Lush (1940), while genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were computed following Burton and Devane (1953) [3] . Broad-sense heritability (h 2 b.s.) was assessed as per Hanson et al., (1956) and classified into low (<30%), moderate (30-60%) and high (>60%) categories as outlined by Johnson et al. (1955) [10] . Expected genetic advance (GA) and genetic advance as a percentage of mean (GAM) were calculated using the formulas of Burton (1953) [3] and Johnson et al., (1955) [10] with GAM categorized as low (<10%), moderate (10-20%) and high (>20%). Genotypic and phenotypic correlation coefficients were computed following Singh and Chaudhary (1985).

Results and Discussion

Analysis of Variance

The analysis of variance for different quantitative characters, as shown in Table 2, revealed that the mean sum of squares due to genotypic differences was highly significant for all characters studied. This indicates a substantial level of variability among the 17 genotypes and 3 check varieties. Specifically, significant variations were observed in developmental and growth parameters, such as days to 50 per cent tasseling (13.02), days to 50 per cent silking (14.67), plant height (211.11 cm) and cob height (150.29 cm). Population and ear physical traits also demonstrated significant differences, including plant count at harvest (76.78), number of cobs per plot (76.52), mean cob length with husk (13.77 cm) and without husk (12.25 cm), mean cob girth with husk (7.14 cm) and without husk (4.95 cm), as well as kernel characteristics like the number of kernel rows per cob (6.68), number of kernels per row (11.86) and 100 kernel weight (23.39 gm). Furthermore, highly significant variation was present in overall productivity and quality profiles, notably cob yield per plant with husk (1101.62 gm), brix percentage (2.31%), reducing sugar percentage (0.59%) and sucrose percentage (12.45%).

Genetic Variability

The range of variability, estimates for the genotypic and phenotypic coefficients of variation (GCV and PCV), heritability in the broad sense (%), genetic advance and genetic advance as a percentage of the mean are given in Table 3. Assessment of variability forms the basis of a successful breeding programme focused on improving yield and quality traits. Hence, estimation of genotypic and phenotypic coefficients of variation is important to understand the nature and magnitude of variation. Genetic variability together with heritability estimates, provides a better understanding of the potential genetic gains from selection (Burton, 1953) [3] .

Range and Mean

Based on mean values which are mentioned in Table 3 and Table 4, The analysis revealed significant variability across the 17 sweet corn characters evaluated in the 20 genotypes. The range for days to 50 per cent tasseling varied from 47.67 to 58.33 days with a mean of 54.23 days while days to 50 per cent silking ranged from 50.00 to 61.33 days with an average of 56.95 days. Plant count at harvest ranged from 63.67 to 80.67 with a mean of 72.20. Number of cobs per plot at harvest varied between 56.00 and 73.67 with an average of 65.05. Mean cob length with husk ranged from 19.23 cm to 26.93 cm with a mean of 23.31 cm whereas mean cob length without husk varied from 16.83 cm to 23.73 cm with an average of 20.22 cm. Mean cob girth with husk ranged from 15.00 cm to 23.17 cm with a mean of 18.75 cm while mean cob girth without husk varied from 13.16 cm to 17.93 cm with an average of 15.98 cm. The number of kernel rows per cob ranged from 12.67 to 17.33 with an average of 15.20 and the number of kernels per row ranged from 31.32 to 39.18 with an average of 36.05. Plant height ranged from 133.00 cm to 166.20 cm with a mean of 152.85 cm while cob height varied between 52.47 cm and 77.93 cm with an average of 61.21 cm. 100 kernel weight ranged from 23.25 gm to 28.12 gm with an average of 23.25 gm. Cob yield per plant with husk ranged from 247.00 gm to 323.00 gm with a mean of 291.95 gm. Quality parameters also showed noticeable variation; Brix percentage ranged from 13.40 per cent to 17.03 per cent with a mean of 14.96 per cent, reducing sugar percentage ranged from 1.67 per cent to 3.27 per cent with an average of 2.19 per cent and sucrose percentage ranged from 17.66 per cent to 24.69 per cent with a mean of 20.86 per cent. The GCV was consistently lower than the PCV for all characters indicating that environmental factors played a role in the expression of these characters, similar result were reported by Dagla et al., (2015) [4] , Niji et al., (2018) [13] , Rajasekar et al., (2024) [15] and Mittal et al., (2026) [12] in sweet corn. [5] and Ahmed et al., (2020) [1] which reported high heritability for characters such as reducing sugar, sucrose, cob height and 100 kernel weight suggesting that these characters are strongly influenced by genetic factors [2] .

Heritability

Conclusion

Significant genetic variability was observed among the 20 sweet corn genotypes for all 17 traits. High heritability with moderate to high genetic advance indicated good selection potential for reducing sugar, sucrose, cob height and 100kernel weight. Genotype 60009 showed the highest cob yield, while PTKSC 25406 showed superior quality traits. These genotypes may be useful for further evaluation and sweet corn breeding.

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