Combining ability studies for seed yield and its component traits in sesame [Sesamum indicum (L.)]

Introduction

Sesame (Sesamum indicum L.) is one of the most ancient and important oilseed crops grown next to groundnut and mustard in India. The oilseed crops play an important role in agriculture and industrial economy of our country. India occupies a very prominent place in the oilseed map of the world as it produces a large variety of oilseed crops and ranks first in respect of total hectarage and production. Sesame can grow well in many ecological regions of tropical and sub-tropical climates, although its cultivation reaches from 40 o N to 40 o S latitude. The sesame is a self-pollinated crop and the genus sesamum belongs to Pedaliaceae family. The genus Sesamum consists of many species but, only Sesamum indicum L. has been recognized as a cultivated species (Ashri, 1998) [1] . According to Kobayashi et al. (1990) [6] , 36 species have been identified of which 22 species have been found in Africa, five in Asia, seven in both Africa and Asia and one species each in Crete and Brazil. There are three cytogenetic groups of which 2n=26 consist of the cultivated S. indicum along with S. alatum, S. capense, S. schenckii, S. malabaricum; 2n=32 consist of S. prostratum, S. laciniatum, S. angolense, S. angustifolium; while S. radiatum, S. occidentale, S. schinzianum belong to 2n=64. Mainly due to the differences in chromosomal numbers across the three cytotaxonomic groups, there is limited cross compatibility among the species. Therefore, it has been difficult to transfer desirable characteristics such as drought tolerance and resistance to diseases and pest, from wild relatives into cultivated sesame (Carlsson et al., 2008) [2] .

Materials and Methods

The current investigation on sesame consisted of 32 genotypes, a line x tester set of twelve (8 lines and 4 testers) parents and their 32 crosses. The experiment was laid out in randomized complete block design (RCBD) with three replications at Main Oilseeds Research Station, Junagadh Agricultural University, Junagadh (Gujarat) during kharif-2022. Observation were recorded for nine traits of five representative plants in each replication on plant height (cm) (PH), number of branches per plant (NBPP), number of capsules per plant (NCP), Length of capsule (cm) (LC), Width of capsule (cm) (WC), number of seeds per capsule (NSPC), Number of capsules per leaf axil (NCPL), 1000-seed weight (g) (TW) and Seed yield per plant (g) (SYP). Data was analysed according to the model given by Kempthorne (1957) [5] to study combining ability variances and effects.

Results and Discussion

The analysis of variance for combining ability exposed that the partitioning of variance among the crosses showed that mean squares due to lines and testers were found significant for all the characters except variance due to testers for plant height and 1000-seed weight (g) when tested against respective error mean square. In case of lines x testers interaction, the mean squares were also significant for all the characters except days width of capsule (cm) (Table 1). The ratio of σ 2 gca / σ 2 sca was less than unity for all the characters (Table 2). This indicated that both additive as well as non-additive genetic variances played a vital role in the inheritance of all these traits under studied. The results were in line with the findings of Kumar et al. (2012) [7] ; Joshi et al. (2015) [3] ; Priya et al. (2016) [8] ; Saxena and Bisen, (2017) [9] ; Virani et al. (2018) [10] ; and Dela et al. (2019) [4] . The magnitude of gca and sca variances revealed that the sca variances were higher than their respective gca variances for all the traits (Table 2). This was further supported by the potent ratio (σ 2 gca/σ 2 sca) less than unity confirmed the preponderance of non-additive gene action for characters under studied and suggested the utility of hybrid breeding approach to exploit existing heterosis in sesame genotypes. Estimation of general combining ability effects (Table 3) revealed that it was difficult to pick up a good combiner for all the characters together as the combining ability effect were not consistent for all the yield attributing characters. the line AT 510 gave desirable gca effect simultaneously for three characters viz., length of capsule (cm), number of capsules per leaf axil and 1000-seed weight (g). Likewise, the line N 62 39 was good general combiner for days to maturity, 1000-seed weight (g) and seed yield per plant (g). Likewise, the line AT 377 was good general combiner for plant height (cm), number of capsules per plant and number of capsules per leaf axil. Specific combining ability effects facilitates the identification of superior cross combinations for development of promising hybrids. Five cross combinations (Table 4) The estimates of sca effect of the crosses indicated that five hybrids manifested significant and positive sca effect for seed yield per plant. These best five specific combinations were AT 522 x GT 3 followed by AT 482 x AT 338, AT 377 x GT 1,IC 204528 X AT-338 and DC-4 X AT-338. The cross AT 522 x GT 3 was also found good specific combiner for number of capsules per plant, number of seeds per capsule, 1000-seed weight (g) and oil content (%) and also showed high per se performance and standard heterosis. Likewise, the cross AT 482 x AT 338 also showed desirable sca effect for number of seeds per capsule, oil content (%) and seed yield per plant (g). The high sca effect observed for seed yield per plant was associated with desirable sca effect manifested by its component characters like number of capsules per plant, number of seeds per capsule and 1000seed weight (g).

Conclusion

In commenced investigation, both GCA and SCA variances were important for all the characters studied with predominance of SCA variance which delineated substantial scope for sesame crop improvement through hybrid breeding. The parents N 62-39, AT 510 and tester AT 338 were found to be good general combiners for seed yield and its attributing traits. The cross combinations with high sca effects were involved in to good × poor, poor × good, average × average and average × poor general combiners. This reflected the role of additive and non-additive gene actions in the genetic control of traits. Under a circumstance where both additive and non-additive gene effects are important, biparental mattings as well as mating of selected plants in early segregating generations should be attempted in developing potential populations having optimum levels of homozygosity and heterozygosity in sesame.

References

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