Harnessing heritability and genetic advance for fruit yield and yield attributes from parents, F1 hybrids and segregating generations in bottle gourd [Lagenaria siceraria (Mol) Standl]

Introduction

Bottle gourd [Lagenaria siceraria (Mol.) Standl.] is one of the earliest domesticated vegetable crops belonging to the family Cucurbitaceae. It is a diploid species with a chromosome number of 2n = 2x = 22 and is monoecious in nature. The crop exhibits a high degree of natural cross-pollination, ranging from 60 to 80 per cent, which contributes to extensive variability in morphological and yield related traits. Bottle gourd is cultivated primarily for its tender fruits, which are easily digestible and possess appreciable nutritional value, containing carbohydrates, minerals and vitamins. In certain tribal communities, dried bottle gourd fruits are traditionally used for making domestic utensils and musical instruments. In India, vegetable cultivation forms an integral part of the horticultural sector and contributes substantially to agricultural growth and rural livelihoods. Recent estimates indicate that the horticultural area reached approximately 29.09 million hectares with a production of 367.70 million tonnes during 2024-25 (Anonymous, 2024) [3] . Despite this progress, average productivity in many regions remains below its attainable genetic potential. In Gujarat, bottle gourd cultivation is predominantly based on locally available landraces characterized by considerable genetic heterogeneity and lack of uniformity, resulting in inconsistent yield performance. Consequently, there exists a pressing need for systematic genetic improvement through scientifically designed breeding programmes. Estimate of heritability serves as a useful guide to the plant breeder. The breeder is able to appreciate the proportion of variation that is due to genotypic (broad-sense heritability) or additive (narrow-sense heritability) effects, which is the portion of genetic variation that is fixable in pure lines. If heritability of a character is very high, selection for the character should be fairly easy because there would be a close correspondence between the genotype and phenotype due to the relatively smaller contribution of the environment to the phenotype. Conversely, for a character with low heritability, selection may be considerably difficult or virtually impractical due to the masking effect of the environment on genotypic effects.

Heritability in narrow sense (h ns

2 ) The narrow-sense heritability, which represents the portion of genetic variation fixable in pure lines, was estimated using the formula suggested by Warner (1952) [40] . The estimation was calculated as follows:

Where, h ns 2 = Heritability in narrow sense VF 2 = Variance of F [27] :

1. Low heritability: 0 -30% 2. Moderate heritability: 30 -60%

High heritability: > 60%

Genetic advance as per cent of mean

Genetic advance (GA) serves as a measure of the gain obtained from phenotypic selection for a particular character. High genetic advance coupled with high heritability estimates offers the most suitable condition for selection. The expected genetic advance at a 5 per cent level of selection intensity was estimated using the formula suggested by Johnson et al. (1955) [22] :

Where, h (ns) 2 = Heritability in narrow sense

Expected genetic advance as per cent of mean (expected genetic gain) was estimated using the following formula: Expected Genetic Advance as % of mean = Genetic advance

X ̅ ×100

Where, X ̅ = Mean of the character under experiment The value of expected genetic advance for various characters was demarcated into three categories according to Johnson et al. (1955) [22]: 1.

Crossing programme

In bottle gourd, anthesis takes place during early morning hours. The female and male flower buds which were likely to open on the following day were selected and covered with butter paper bags during evening hours to avoid contamination by foreign pollen. On the day of anthesis, the bags were carefully removed in the morning hours. The pollen from freshly opened male flowers of the desired parent was collected and gently rubbed on the receptive stigma of the female flower. After pollination, the flowers were immediately covered again with butter paper bags and properly tagged indicating the name of the cross and date of pollination. For maintenance of parental lines and production of F₂ seeds, selfing was carried out by pollinating the female flower with pollen from the same plant and re-bagging the flower after pollination. The F₁ seeds of four crosses were produced. Then F₂ generation was developed by selfing F₁ plants, whereas backcross generations (BC₁ and BC₂) were developed by crossing F₁ with respective P₁ and P₂ parents. The seeds obtained from successful pollinations were extracted from fully mature fruits, dried properly and stored for further evaluation. List of crosses used for present experiment mentioned in Table 2.

Evaluation programme

All six generations viz., P₁, P₂, F₁, F₂, BC₁ and BC₂ of the four crosses were evaluated at the Centre for Vegetable Research, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat during Kharif 2024. The experimental material was evaluated in a Compact Family Block Design (CFBD) with three replications. Each replication was divided into four family blocks representing individual crosses and each family block consisted of six generations. Each block comprised eleven rows consisting of one row each of P₁, P₂ and F₁, four rows of F₂ and two rows each of BC₁ and BC₂ generations. The crop was raised by following the recommended agronomic practices and necessary plant protection measures to ensure successful crop growth and development. ] and the results are presented in Table 3. The analysis of variance between families (crosses) revealed that the mean squares due to crosses were highly significant for all the characters studied. Likewise, significant differences among generations were observed for all the characters in all the four crosses, indicating the existence of substantial variability among the generations derived from the respective parental combinations. The significant variation observed among generations suggested the presence of adequate genetic variability for fruit yield and its component traits, thereby providing sufficient scope for generation mean analysis and interpretation of gene effects. The existence of considerable variability among the generations may be attributed to the genetic divergence among the parental lines involved in the crosses. Such variability among the generations is essential for effective selection and genetic improvement of yield and its associated traits in bottle gourd. [23] , Srirom and Yadav (2021) [34] , Dubey et al. (2022) [13] , Duhan et al.

(2022) [14] , Das et al. (2024) [9] and Suman et al. (2024) [35] .

Days to first female flower appearance

Highest narrow-sense heritability was observed in GPBG 108 × ABGS 14-25 with 83.11%, whereas the lowest heritability was observed in ABG 1 × ABGS 14-25 with 40.11%. Highest genetic advance was observed in GPBG 108 × ABGS 14-25 with 5.65% and lowest genetic advance was observed in ABG 1 × ABGS 14-25 with 2.11%. High heritability coupled with low genetic advance was observed in GPBG 108 × ABGS 14-25, whereas moderate heritability coupled with low genetic advance was observed in ABG 1 × ABGS 14-25. These results indicated non-additive gene action and selection may not be rewarding. Similar findings were reported by Srirom et al. (2021) [34] , Venkataraman et al. (2021), Dubey et al. (2022) [13] , Duhan et al. (2022) [14] , Harika et al. (2024) [18] , Suman et al. (2024) [35] , Das et al.

(2024) and Kumar et al. (2025) [25] .

node number at which first male flower appearance Highest narrow-sense heritability was observed in GPBG 108 × ABGS 14-25 with 193.36%, whereas the lowest heritability was observed in ABG 1 × ABGS 14-25 with 3.84%. Highest genetic advance was observed in GPBG 108 × ABGS 14-25 with 209.67% and lowest genetic advance was observed in ABG 1 × ABGS 14-25 with 0.76%. High heritability coupled with high genetic advance was observed in GPBG 108 × ABGS 14-25, which indicated additive gene action and selection may be effective. Low heritability coupled with low genetic advance was observed in ABG 1 × ABGS 14-25, which indicated non-additive gene action and selection may not be rewarding. Similar findings were reported by Sharma and Sengupta (2013) [28] , Deepthi et al.

(2016) [11] , Chikkeri et al. (2018) [6] , Varalakshmi et al.

(2018) [37] , Kandasamy et al. (2021), Dubey et al. (2022) [13] and Harika et al. (2024). However, similar observations were also reported by Srirom et al. (2021) [34] , Venkataraman et al. (2021), Bashir et al. (2024) [5] and Kumar et al. (2025) [25] , who reported low or moderate heritability coupled with low or moderate genetic advance and suggested non-additive gene action and selection may not be rewarding.

Node number at which first female flower appearance

No estimable estimates of narrow-sense heritability and genetic advance were obtained for node number at which first female flower appearance in any of the four crosses. Therefore, meaningful interpretation regarding the nature of gene action and effectiveness of selection could not be made for this trait.

Number of branch per plant

For number of branch per plant, moderate narrow-sense heritability was observed in GPBG 108 × ABGS 14-25 with 58.51%, whereas no estimable heritability was observed in GPBG 108 × ABGS 11-24, ABG 1 × ABGS 14-25 and NDBG 132 × ABGS 14-25. Genetic advance was observed only in GPBG 108 × ABGS 14-25 with 9.17%. Moderate heritability coupled with low genetic advance was observed in GPBG 108 × ABGS 14-25, which indicated non-additive gene action and selection may not be rewarding. The results of the present investigations are in conformity with the findings of Dubey et al. (2022) [13] , Duhan et al. (2022) [14] ,

Band et al. (2024) [4] , Das et al. (2024) [9] and Harika et al.

(2024) [18] , who reported moderate or high heritability coupled with low genetic advance and suggested nonadditive gene action and selection may not be rewarding.

No estimable estimates of narrow-sense heritability and genetic advance were obtained for fruit length in any of the four crosses. Therefore, meaningful interpretation regarding the nature of gene action and effectiveness of selection could not be made for this trait.

In fruit girth, highest narrow-sense heritability was observed in GPBG 108 × ABGS [28] , Deepthi et al. (2016) [11] , Chikkeri et al. (2018) [6] , Varalakshmi et al.

(2018) [37] , Kandasamy et al. (2019) [13] , Dubey et al. (2022) [13] , Suman et al. (2024) [35] and Yogesh Kumar et al. (2025) [25] , who reported high heritability coupled with high or moderate genetic advance and suggested additive gene action and effectiveness of selection.

Highest narrow-sense heritability was observed in NDBG 132 × ABGS 14-25 with 93.64%, followed by ABG [28] , Deepthi et al.

(2016) [11] , Varalakshmi et al. (2018) [37] , Kandasamy et al.

(2019) [23] , Ahmad et al. (2022), Dubey et al. (2022) [13] , Duhan et al. (2022) [14] , Band et al. (2024) [4] and Das et al.

(2024) [9] . However, similar observations were also reported by Srirom and Yadav (2021) [34] , Venkataraman et al.

(2021), Bashir et al. (2024) [5] and Suman et al. (2024) [35] , who reported low or moderate heritability coupled with low or moderate genetic advance and suggested non-additive gene action and selection may not be rewarding. [2] , who reported low heritability coupled with low genetic advance and suggested nonadditive gene action and selection may not be rewarding.

Number of fruit per plant

Low narrow-sense heritability was observed in ABG 1 × ABGS 14-25 with 20.63%, whereas no estimable heritability was observed in GPBG 108 × ABGS 11-24, GPBG 108 × ABGS 14-25 and NDBG 132 × ABGS 14-25. Genetic advance was observed only in ABG 1 × ABGS 14-25 with 2.03%. Low heritability coupled with low genetic advance was observed in ABG 1 × ABGS 14-25, which indicated non-additive gene action and selection may not be rewarding. However, the findings are also supported by Varalakshmi et al. (2018) [37] , Kumar et al. (2021) [24] , Srirom and Yadav (2021) [34] , Venkataraman et al. (2021) and Bashir et al. (2024) [5] , who reported low heritability and suggested non-additive gene action and selection may not be rewarding.

Highest narrow-sense heritability was observed in GPBG 108 × ABGS 11-24 with 78.58%, followed by NDBG 132 × ABGS 14-25 with 70.05%, whereas no estimable heritability was observed in GPBG 108 × ABGS 14-25 and ABG 1 × ABGS

Conclusion

The heritability estimates along with genetic advance is normally more helpful in predicting the gain under selection than heritability alone. High to moderate heritability coupled with moderate to high genetic advance was observed in node number at which first male flower appearance in cross (GPBG 108 × ABGS 14-25) and in average fruit weight in crosses (ABG 1 × ABGS 14-25) and (NDBG 132 × ABGS 14-25). It revealed that these crosses were controlled by additive genes and hence simple selections should lead to a fast genetic improvement of the genotypes used in the study. Some crosses showed high to medium narrow sense heritability coupled with low genetic advance, so bi-parental mating or few cycles of recurrent selection should be used for improvement in such characters. Crosses with low narrow sense heritability coupled with low genetic advance indicated presence of non-additive type of gene action and selection should not be rewarding for these characters.

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