Combining ability analysis for yield and yield contributing traits in pumpkin

Introduction

Pumpkin (Cucurbita moschata) is an important cucurbitaceous vegetable crop grown throughout tropical and subtropical regions, including India. It has a chromosome number of 2n = 40 and is a vigorous, annual, running or trailing vine characterized by large, bristly leaves and prominent yellow flowers. Pumpkin is well known for its high carotene content in the fruit and serves as an excellent source of vitamin A (972 IU per 100 g of edible portion), which plays a vital role in providing antioxidants, particularly carotenoids, in the human diet (Hidaka et al., 1987) [5] . Pumpkin is one of the widely cultivated vegetables in India, with a total area of 106 million hectares and an annual production of 2205 million metric tonnes (Anon, 2022) [1] . Pumpkin is a monoecious and highly cross-pollinated crop, offering ample scope for the successful exploitation of hybrid vigour (heterosis). It has received limited attention, even though the crop shows high variation due to cross-pollination. Most available hybrids produce large fruits, which are less suitable for present-day nuclear families. Therefore, there is a need to develop medium-sized, high-yielding pumpkin hybrids with better quality traits for consumer preference, easy packaging and transportation. Since pumpkin is a highly cross-pollinated crop, exploitation of heterosis through hybrid breeding offers great scope for crop improvement. The identification of suitable parents with good combining ability is an important prerequisite for successful hybrid development. Combining ability analysis helps in understanding the nature and magnitude of gene action involved in the inheritance of various quantitative characters. The variance of GCA includes the additive nature of the total variance, whereas SCA includes non-additive nature of the total variance, arising largely from dominance and epistatic deviations (Malik et al., 2004). The knowledge on the relative importance of the additive (GCA) and non-additive (SCA) gene actions within a breeding population is significant because it determines the breeding method for genetic improvement (Sincik, 2005) [14] . Line × tester analysis is widely used to estimate combining ability effects and to identify superior parental lines and promising hybrids. Several studies in cucurbits have revealed the importance of both additive and non-additive gene action for yield and quality traits. For the development of superior hybrids, estimates of general combining ability of parents and specific combining ability of the crosses help in proper selection of parents for hybridization (Dogra and Kanwar, 2001) [2] . In this context, the present investigation was undertaken to evaluate pumpkin hybrids for yield and quality traits and to identify promising parental combinations for future breeding programmes.

Material and methods

The Line × Tester mating design proposed by Kempthorne (1957) was used for the development of hybrids. Six lines IC-608054(L1), IC-284729 (L2), IC-599437 (L3), IC-608052 (L4), IC-599403 (L5), AKL-1 (L6) were crossed with five testers), IC-332324 (T1), AKL-4 (T2), IC-320175 (T3), IC-599410 (T4) and AMT-1 (T5) to obtain thirty F₁ hybrids during Kharif-2022. The resulting hybrids along with parents and standard check were evaluated in Randomized Block Design (RBD) with two replications during summer-2023 and Kharif-2023 at the Instructional farm, department of vegetable science, faculty of horticulture, Dr. Panjabrao Deshmukh Krishi Vidyapeetth, Akola, Maharashtra. Observations were recorded on yield and yield contributing traits, and combining ability analysis was carried out to estimate general combining ability (GCA) and specific combining ability (SCA) effects. The plants were spaced at a distance of 3 m between rows and 1.0 m within plants.

Result and Discussion

The analysis of variance presented in Table 1 revealed highly significant differences among genotypes, crosses, lines, testers and Line × Tester interactions for most of the characters studied during both summer and kharif seasons. This indicates the presence of substantial genetic variability among the parental lines and hybrids for yield and yield contributing traits in pumpkin. The analysis of variance revealed highly significant differences among genotypes for all the traits, indicating the presence of substantial genetic variability and scope for selection in pumpkin. Significant mean squares due to lines and testers suggested the importance of additive gene action, whereas significant Line × Tester interactions for most traits indicated the predominance of non-additive gene action. The significant SCA variances for fruit yield, fruit weight, fruit diameter and flowering traits suggested ample scope for heterosis breeding in pumpkin improvement. Overall, both additive and non-additive gene actions governed the inheritance of yield and related traits, with non-additive gene action playing a major role for economically important characters. Therefore, exploitation of heterosis through hybrid breeding along with selection of good combiners would be effective for the improvement of pumpkin. Similar findings in cucumber by Mule et al. (2012) [10] and in pumpkin were reported by Kumar et al. (2018) [7] who observed significant combining ability variances for yield and related traits in cucurbits.

General combining ability

The general combining ability is the performance of genotypes in several hybrid combinations. It is estimated from sib families. Dhillon (1975) suggested that combining ability [10] in cucumber, Singh et al. (2013) [15] in bittergourd, Nisha and Veeraragavathatham (2014) [12] in pumpkin, Hatwal et al.

(2018) [3] in pumpkin, Yadav et al. (2021) [17] in pumpkin.

Specific combining ability

Specific combining ability refers to the performance of a particular cross in relation to the average performance of the parents involved. High SCA effects suggest that certain parental combinations perform better than expected based on their general combining ability.

For fruit yield per vine, the cross IC-618054 × IC-320175 recorded superior per se performance with fruit yield of 13.88 kg and 14.11 kg during summer and kharif seasons, respectively. The cross also exhibited significant positive SCA effects of 2.53 and 1.93, indicating strong non-additive gene action for fruit yield. The hybrid AKL-1 × IC-320175 also showed excellent performance with fruit yield per vine of 13.70 kg and 14.50 kg along with positive SCA effects of 1.55 during kharif season. This cross also exhibited desirable performance for earliness traits such as days to male flowering (44. [16] in pumpkin, Mohanty et al. (2000) [9] in pumpkin, Muthal et al. (2018) [11] in pumpkin, Rajaguru et al. (2020) [13] in cucumber, Harshini et al. (2024) [4] in pumpkin.

Conclusion

The present study revealed significant genetic variability among the parents and hybrids for yield and quality traits in pumpkin. Both additive and non-additive gene actions were involved in the inheritance of different characters; however, non-additive gene action predominated for fruit yield and related traits, indicating the usefulness of heterosis breeding. Among the parents, IC-618054, AKL-1, IC-618052 and IC-599410 were identified as good general combiners for yield and quality traits. Among the hybrids, IC-618054 × IC-320175, AKL-1 × IC-320175, IC-618054 × IC-599410 and IC-618052 × IC-599410 exhibited superior per se performance along with significant positive SCA effects for fruit yield and associated characters. Therefore, these parents and hybrids may be effectively utilized in future pumpkin breeding programmes for the development of high yielding, early and quality hybrids suitable for commercial cultivation.

Future Scope

The promising hybrids identified in the present study may be utilized in future breeding programmes for developing high yielding and quality pumpkin hybrids. Superior combiners can be exploited in heterosis breeding due to the predominance of non-additive gene action. Further multilocation and disease resistance studies are needed for commercial utilization of these hybrids.

Acknowledgement

AcknowledgementI extend my sincere thanks to my research guide Dr. A. P. Wagh and to my advisory committee members for giving me proper guidance throughout the course of study.

References

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