Genetic components of variance for fruit yield and its contributing traits in Brinjal [Solanum melongena L.]

Introduction

Brinjal (Solanum melongena L., 2n = 24) is an important vegetable crop belonging to the family Solanaceae, widely cultivated in tropical and subtropical regions of India. It is known by various vernacular names such as Ringan, Baingan, Vangi and Katharikai is believed to have originated in the Indo-Burma region. Due to its high yield potential, adaptability and affordability, it is often referred to as the "poor man's vegetable". Brinjal is nutritionally rich, containing vitamins such as ascorbic acid, niacin and vitamin B-complex, along with essential minerals and antioxidant compounds like anthocyanins. India is the second largest producer of brinjal in the world, with wide cultivation across major states including Gujarat. The crop exhibits considerable genetic variability in plant growth and fruit characteristics, offering great scope for genetic improvement. However, fruit yield is a complex quantitative trait governed by multiple component characters and their interactions. Therefore, understanding the genetic architecture of yield and its contributing traits is essential for effective selection and crop improvement. Diallel analysis based on Hayman's approach provides a detailed understanding of gene action by partitioning genetic variance into additive (D), dominance (H₁ and H₂) and environmental (E) components. These parameters also help in estimating the degree of dominance and distribution of alleles among parental lines. Knowledge of these genetic components is useful in deciding appropriate breeding strategies, where additive effects favor selection methods, while dominance effects support heterosis breeding. Thus, the study of genetic components of variance plays a crucial role in identifying suitable parents and developing high yielding hybrids or varieties for sustainable improvement in brinjal.

Materials and Methods

The experimental material comprised of parents and their F₁'s derived by crossing among nine parents viz., JBR-24-14, JBR-24-13, JBR-24-12, JBR-24-11, GJB-3, GJLB-4, GRB-7, Pant Rituraj and Pusa Kranti in a half-diallel fashion (Table 1). Row to row and plant to plant spacing was maintained at 60 cm × 30 cm. To produce a better crop, the recommended agronomic practices of the region were followed. The nine parental lines were selected based on morphological variability for growth, maturity, fruit size, fruit shape, fruit yield and yield contributing traits in brinjal. The experiment was laid out in a randomized block design with three replications during rabi 2025-26 at the Vegetable Research Station, Junagadh Agricultural University, Junagadh. Observations were recorded on sixteen characters viz., days to first flowering, days to first picking, number of fruits per plant, fruit length (cm), average fruit weight (g), fruit girth (cm), number of branches per plant, plant height (cm), days to last picking, number of pickings, total fruit yield per plant (kg), total soluble solids, fruit borer infestation (%), shoot borer infestation (%), Vitamin-C content and total anthocyanin pigment and the mean data were used for statistical analysis. The total variation among F₁ hybrids was analyzed following Hayman's diallel approach ( 3 Hayman, 1954a, 4 Hayman 1954b) to estimate genetic components of variance. The genetic parameters viz., additive variance (D), dominance variance (H₁ and H₂), covariance of additive and dominance effects (F) and environmental component (E) were estimated. Further, the degree of dominance (H1/D) 1/2 , proportion of positive and negative alleles (H₂/4H₁) and the ratio of dominant to recessive genes (KD/KR) were computed to understand the nature and distribution of gene effects.

Results and Discussion

The estimate of the components of variation revealed significant differences was examined for variance due to additive genetic effect (D) for all the traits (except days to first flowering, days to first picking, number of fruits per plant, fruit length, number of primary branches per plant, plant height, total fruits yield per plant and vitamin-c) implying importance of both additive and non-additive gene effect. Notwithstanding, additive component was lower in magnitude than both dominance components for all the traits, which showing the predominance of non-additive gene action in the expression of all the traits. (Table 1) Genetic analysis exhibited that T2 values were non-significant for all the characters (except fruit length, fruit girth, number of primary branches per plant, days to last picking, total soluble solids and vitamin-c). This recommended that additivedominance model was adequate for all the traits except above listed. The non-significant estimate of 'E' for all the traits (except days to first picking, days to last picking and number of picking) point out that there was no considerable environmental influence modifying their expression. The average degree of dominance (H1/D) 1/2 was found to be more than unity for all the traits indicating over dominance type of gene action, which suggested that heterosis breeding might be advantageous to get higher gain in brinjal. Asymmetrical distribution of positive and negative genes in the parental lines was revealed from the estimate, H2/4H1 for all the characters under studied. The KD/KR ratio showed an excess of dominant genes in the parent than recessive genes for all the characters except days to first flowering, number of fruits per plant, number of primary branches per plant, shoot borer infestation and total anthocyanin pigment. All the traits show moderated heritability (except days to first flowering, number of fruits per plant, number of primary branches per plant and shoot borer infestation shows high heritability, where in case, of vitamin-c had low heritability). (Table 1) In general, narrow sense heritability was found to be less than 50 per cent for days to first flowering, days to first picking, fruit length, average fruit weight, fruit girth, number of primary branches per plant, number of fruits per plant, days to last picking, number of pickings, plant height, total fruit yield per plant, total soluble solids, vitamin-c and fruit and shoot borer infestation suggesting major role of dominance gene action in the expression of this trait. High narrow sense heritability for total anthocyanin pigment indicated that major part of phenotypic variability was due to addictiveness and possibility of fixing these traits by simple selection. (Table 1) These findings are in concurrence with results of These findings are in concurrence with results of 6 Yadav et al. (2017), 5 For days to first flowering, the dominance components (H₁ and H₂) were found significant, indicating the importance of dominance effects in its inheritance. The non-significant h² value suggested ambidirectional dominance. The average degree of dominance (H1/D) 1/2 was greater than unity (2.92), indicating over-dominance. The H₂/4H₁ ratio (0.24) revealed nearly symmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (0.83) along with negative F value (-0.54) indicated a higher proportion of recessive alleles. Narrow sense heritability was moderate (22.20%), suggesting limited effectiveness of selection for this trait. In contrast, days to first picking exhibited significant dominance components (H₁ and H₂) with values exceeding the additive component (D), indicating predominance of over-dominance. The significant h² value reflected directional dominance, while the significant environmental component (E) suggested considerable environmental influence. The degree of dominance (H1/D) 1/2 was 3.51, further confirming over-dominance. The H₂/4H₁ ratio (0.20) indicated asymmetrical distribution of alleles, whereas the KD/KR ratio (1.56) along with a positive F value (2.19) suggested a higher frequency of dominant alleles. The h²/H₂ ratio (0.38) indicated that the number of gene groups could not be precisely estimated and the narrow sense heritability was moderate (16.70%), indicating limited effectiveness of direct selection. For number of fruits per plant, the dominance components (H₁ and H₂) were found to be significant, indicating the major role of non-additive gene effects in the inheritance of this trait. The higher magnitude of dominance variance compared to the additive component (D) suggested the prevalence of overdominance. The significant h² value indicated the presence of directional dominance. The non-significant environmental component (E) implied that environmental influence on this trait was minimal. The average degree of dominance (H1/D) 1/2 was 8.14, confirming strong over-dominance. The H₂/4H₁ ratio (0.24) indicated a nearly symmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (0.96) along with the negative F value (-0.53) suggested a relatively higher proportion of recessive alleles. The h²/H₂ ratio (0.16) indicated that the number of effective gene groups governing the trait could not be precisely estimated. The narrow sense heritability was low (6.80%), suggesting limited scope for improvement through direct selection. For fruit length, the dominance variance components (H₁ and H₂) were significant, indicating the prominent role of dominance effects in its inheritance. The magnitude of dominance components exceeding the additive component (D) suggested the prevalence of over-dominance for this trait. The nonsignificant h² value indicated the absence of clear directional dominance. The environmental component (E) was nonsignificant, implying minimal environmental influence on trait expression. The average degree of dominance (H1/D) 1/2 was 3.35, confirming over-dominance. The H₂/4H₁ ratio (0.22) indicated an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (1.52) along with a positive F value (0.93) suggested a higher proportion of dominant alleles in the parental lines. The h²/H₂ ratio (0.00) indicated that the number of effective gene groups controlling the trait could not be reliably estimated. The narrow sense heritability was low (13.70%), indicating limited effectiveness of direct selection for improvement of this trait. Analysis of genetic components for average fruit weight revealed that both additive (D) and dominance (H₁ and H₂) variances were significant, indicating the involvement of both gene effects in its inheritance. The non-significant h² value suggested ambidirectional dominance, while the non-significant environmental component (E) indicated negligible environmental influence on this trait. The average degree of dominance (H1/D) 1/2 was 2.20, indicating over-dominance. The H₂/4H₁ ratio (0.22) reflected an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (1.16), along with a positive F value (32.44), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (-0.008) indicated that the number of effective gene groups controlling the trait could not be reliably estimated. The narrow sense heritability was moderate (34.20%), suggesting moderate scope for improvement through selection. Estimates of genetic variance components indicated that both additive (D) and dominance (H₁ and H₂) effects were significant, suggesting their involvement in the inheritance of fruit girth. The higher magnitude of dominance variance compared to additive variance reflected the predominance of over-dominance for this trait. The significant h² value pointed towards directional dominance, while the non-significant environmental component (E) indicated minimal environmental influence on its expression. The average degree of dominance (H1/D) 1/2 was 2.03, confirming over-dominance. The H₂/4H₁ ratio (0.19) revealed an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (2.37), along with a positive F value (0.56), suggested a greater proportion of dominant alleles.

The h²/H₂ ratio (1.17) indicated the involvement of dominant gene groups controlling the trait. The narrow sense heritability was low (10.20%), suggesting limited effectiveness of selection for improvement. Variation in genetic parameters showed that dominance components (H₁ and H₂) were significant and exceeded the additive component (D), indicating the predominance of overdominance in controlling number of primary branches per plant. The significant h² value suggested the presence of directional dominance, whereas the non-significant environmental component (E) indicated minimal environmental influence on trait expression. The average degree of dominance (H1/D) 1/2 was 1.94, supporting over-dominance. The H₂/4H₁ ratio (0.23) indicated an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (0.78), along with a negative F value (-0.05), suggested a relatively higher proportion of recessive alleles. The h²/H₂ ratio (0.30) indicated that the number of effective gene groups governing the trait could not be precisely estimated. The narrow sense heritability was low (11.10%), indicating limited scope for improvement through direct selection.

Estimates of genetic variance components indicated that dominance effects (H₁ and H₂) were significant, highlighting the importance of non-additive gene action in the inheritance of plant height. The non-significant h² value suggested ambidirectional dominance, while the non-significant environmental component (E) indicated minimal environmental influence on this trait. The average degree of dominance (H1/D) 1/2 was 2.66, suggesting over-dominance. The H₂/4H₁ ratio (0.21) revealed an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (1.24), along with a positive F value (57.93), indicated a higher proportion of dominant alleles. The h²/H₂ ratio (-0.003) suggested that the number of effective gene groups controlling the trait could not be reliably estimated. The narrow sense heritability was relatively high (30.70%), indicating better prospects for improvement through selection. Evaluation of genetic parameters indicated that both additive (D) and dominance (H₁ and H₂) components were significant, suggesting the involvement of both gene effects in the inheritance of days to last picking, with dominance variance exceeding the additive component and indicating overdominance. The non-significant h² value suggested ambidirectional dominance, while the significant environmental component (E) indicated a considerable influence of environment on trait expression. The average degree of dominance (H1/D) 1/2 was 1.74, supporting over-dominance. The H₂/4H₁ ratio (0.18) indicated an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (2.70), along with a positive F value (73.92), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (-0.01) indicated that the number of effective gene groups controlling the trait could not be precisely estimated. The narrow sense heritability was moderate (15.10%), indicating limited effectiveness of selection for improvement of this trait. Assessment of genetic parameters indicated that both additive (D) and dominance (H₁ and H₂) components were significant, suggesting the involvement of both gene effects in the inheritance of number of pickings, with dominance variance showing a relatively greater influence and indicating overdominance. The significant h² value reflected the presence of directional dominance, while the significant environmental component (E) indicated a substantial environmental effect on trait expression. The average degree of dominance (H1/D) 1/2 was 2.16, confirming over-dominance. The H₂/4H₁ ratio (0.20) indicated an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (2.16), along with a positive F value (0.74), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (1.40) indicated the involvement of dominant gene groups controlling the trait. The narrow sense heritability was very low (7.10%), indicating poor scope for improvement through direct selection. Estimation of genetic parameters indicated that dominance components (H₁ and H₂) were significant, highlighting the major role of non-additive gene effects in the inheritance of total fruit yield per plant, with dominance variance exceeding the additive component (D) and suggesting over-dominance. The nonsignificant h² value indicated ambidirectional dominance, while the non-significant environmental component (E) suggested minimal environmental influence on this trait. The average degree of dominance (H1/D) 1/2 was 3.35, confirming overdominance. The H₂/4H₁ ratio (0.23) indicated an asymmetrical distribution of positive and negative alleles among the parents.

The KD/KR ratio (1.46), along with a positive F value (0.51), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (0.004) indicated that the number of effective gene groups controlling the trait could not be reliably estimated. The narrow sense heritability was low (7.60%), indicating limited scope for improvement through direct selection.

In brinjal, estimates of genetic parameters indicated that both additive (D) and dominance (H₁ and H₂) components were significant for total soluble solids, suggesting the involvement of both gene effects in its inheritance, with dominance variance exceeding the additive component and indicating overdominance. The non-significant h² value suggested ambidirectional dominance, while the negligible environmental component (E) indicated minimal environmental influence on the expression of this trait. The average degree of dominance (H1/D) 1/2 was 1.72, confirming over-dominance. The H₂/4H₁ ratio (0.19) indicated an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (1.80), along with a positive F value (0.49), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (0.16) indicated that the number of effective gene groups controlling the trait could not be precisely estimated. The narrow sense heritability was high (36.60%), indicating better prospects for improvement through selection. Genetic parameter estimates revealed that both additive (D) and dominance (H₁ and H₂) components were significant for fruit borer infestation, indicating the involvement of both gene effects in its inheritance, with dominance variance being relatively higher and suggesting over-dominance. The non-significant h² value indicated ambidirectional dominance, while the nonsignificant environmental component (E) suggested minimal environmental influence on the expression of this trait. The average degree of dominance (H1/D) 1/2 was 2.04, confirming over-dominance. The H₂/4H₁ ratio (0.21) indicated an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (1.30), along with a positive F value (1.42), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (0.09) indicated that the number of effective gene groups controlling the trait could not be precisely estimated. The narrow sense heritability was high (35.40%), indicating good scope for improvement through selection. Estimation of genetic components indicated that both additive (D) and dominance (H₁ and H₂) variances were significant for shoot borer infestation, suggesting the involvement of both gene effects in its inheritance, with dominance variance being relatively higher and indicating over-dominance. The significant h² value reflected the presence of directional dominance, while the non-significant environmental component (E) indicated minimal environmental influence on this trait. The average degree of dominance (H1/D) 1/2 was 2.16, confirming overdominance. The H₂/4H₁ ratio (0.23) indicated an asymmetrical distribution of positive and negative alleles among the parents.

The KD/KR ratio (0.94), along with a negative F value (-0.05), suggested a relatively higher proportion of recessive alleles. The h²/H₂ ratio (0.91) indicated that the number of effective gene groups controlling the trait could not be precisely estimated. The narrow sense heritability was moderate (35.80%), indicating moderate scope for improvement through selection. Genetic parameter estimates indicated that dominance components (H₁ and H₂) were significant for vitamin-c content, highlighting the importance of non-additive gene effects in its inheritance. The non-significant h² value suggested ambidirectional dominance, while the non-significant environmental component (E) indicated minimal environmental influence on the expression of this trait. The average degree of dominance (H1/D) 1/2 was 2.74, indicating over-dominance. The H₂/4H₁ ratio (0.20) revealed an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (2.19), along with a positive F value (1.35), suggested a higher proportion of dominant alleles. The h²/H₂ ratio (0.23) indicated that the number of effective gene groups controlling the trait could not be precisely estimated. The narrow sense heritability was low (5.40%), indicating limited scope for improvement through direct selection.

In brinjal, estimates of genetic parameters indicated that both additive (D) and dominance (H₁ and H₂) components were significant for total anthocyanin pigment, suggesting the involvement of both gene effects in its inheritance, with dominance variance exceeding the additive component and indicating over-dominance. The non-significant h² value suggested ambidirectional dominance, while the negligible environmental component (E) indicated minimal environmental influence on the expression of this trait. The average degree of dominance (H1/D 1/2 was 1.23, indicating over-dominance. The H₂/4H₁ ratio (0.19) revealed an asymmetrical distribution of positive and negative alleles among the parents. The KD/KR ratio (0.74), along with a negative F value (-50.60), suggested a higher proportion of recessive alleles. The h²/H₂ ratio (0.39) indicated that the number of effective gene groups controlling the trait could not be precisely estimated. The narrow sense heritability was high (74.00%), indicating good scope for improvement through selection.

Conclusion

The present investigation revealed the presence of considerable genetic variability among the studied genotypes for yield and its component traits in brinjal. The estimates of genetic components of variance indicated that dominance components were higher in magnitude than additive components for most of the traits, suggesting the predominance of non-additive gene action. The average degree of dominance further confirmed over-dominance for the majority of characters. The distribution of alleles among parents was found to be asymmetrical for most traits, with a higher proportion of dominant alleles in several cases. Environmental influence was minimal for most traits, indicating stability in expression. Heritability estimates varied from low to high, suggesting differential scope for selection across traits. The predominance of non-additive gene effects indicated that simple selection would be less effective for yield improvement. Therefore, exploitation of heterosis through hybrid breeding is recommended as an efficient approach. The superior performance of certain crosses indicated the presence of desirable gene combinations. Overall, heterosis breeding can be effectively utilized for enhancing fruit yield and quality traits in brinjal.

References

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