Half diallel analysis for combining ability and gene action of yield and yield contributing traits in bread wheat (Triticum aestivum L.)

Introduction

Wheat (Triticum aestivum L., 2n=6x=42, AABBDD) plays a vital role in maintaining global food security, contributing for nearly 30% of total grain production and accounting about half of the grain traded across international markets. It is a primary staple crop in more than 40 countries and serves as a significant source of dietary energy and protein for a large portion of the world's population. With the global population expected to reach approximately 9.1 billion by 2050, the demand for wheat is projected to increase substantially, indicating the urgent need to improve its productivity and overall production to fulfill for future food requirements (Maity et al., 2024) [10] . Wheat is rich essential nutrient and noted a high content of important components like as carbohydrates (60-80%), proteins (8-15%), fats (1.5-2%), dietary fiber (about 2.2%), as well as vitamins like as B and E, and various amino acids. Furthermore, the presence of gluten makes wheat particularly suitable for food processing. Owing to its unique gluten properties, wheat is widely used in the preparation of high-quality bread, with gluten content in bread wheat typically ranging from 30 to 35% (Aziz et al., 2019) [2] . Improving the nutritional quality of wheat along with its agronomic performance require the identification of genetically superior parents and a thorough understanding of the genetic architecture governing yield and quality characters, like as protein, iron (Fe), and zinc (Zn) content. Combining ability analysis offers an effective method to assess the relative contribution of additive and nonadditive gene actions and to select suitable parental combinations for hybrid development as well as selection-based breeding program. Among various methods, diallel mating designs are widely utilized for estimating general combining ability (GCA), specific combining ability (SCA), heterosis, and for knowledge of genetic basis of characters inheritance (Jaiswal et al., 2013, Owusu et al., 2020) [6,12] . General combining ability (GCA) offers valuable insight into the performance of genotypes across various hybrid combinations, thereby enhancing effective phenotypic selection (Longin et al., 2013) [9] . Specific combining ability (SCA) indicates the variation reported in particular cross combinations arising due to dominance and epistatic gene interactions. It is therefore useful in identifying superior hybrid combinations and plays a key role in the exploitation of heterosis (Kumari et al., 2015) [7] . The present study the results of gene action, general combining ability, and specific combining ability in 45 F 1 s crosses developed by 10 wheat varieties. The goal was to identification superior genotypes with strong GCA and crosses with the potential to significantly improve wheat yields in the future.

Materials and Methods

The present investigation was evaluated at Student Instructional farm, Peeli Kothi, Tilak Dhari Post graduate College, Jaunpur, Uttar Pradesh, during rabi season 2024-2025 in randomized block design with three replications. The experiment was carried out with 10 parents and 45 hybrids using half diallel mating design. Ten genetically diverse genotypes, exhibited silent features like disease resistance, yield potential, abiotic stress tolerance and quality parameters were selected as parents for hybridization (Table 1). Observations of fourteen traits viz., days to heading, days to anthesis, days to maturity, Grain filling duration, plant height (cm), Effective tillers per plant, chlorophyll content, spike length (cm), number of spikelets per spike, number of grains per spike, 1000-grain weight (g), grain yield per plant (g), biological yield per plant (g) and harvest index (%). Biometrical analysis: The gene action and combining ability estimation have been done using Griffing's (1956) [5] Method 2 Model I.

Results

Analysis of variance findings revealed that both general combining ability (GCA) and specific combining ability (SCA) was highly significant for all the fourteen traits. Grain yield, being a complex trait, indicate significant contributions from both general combining ability (4.2696**) and specific combining ability (2.2686**) sources of variation. Similarly, 1000-seed weight, an important yield-contributing trait, also showed significant general combining ability (18.7885**) and specific combining ability (16.7728**) effects. The predominance of non-additive gene action was demonstrate by the GCA/SCA variance ratio being less than one, suggesting that SCA variance was higher than GCA variance (Table 2). Overall, the findings suggest the involvement of both additive and nonadditive gene actions in the inheritance of the traits, similar result were reported by Kumar et al., (2015) [8] , Bharat Bhushan et al., (2018) [3] Ranjitha et al., (2018) [14] , Ramadan et al., (2018) [13] , Ahmad et al., (2024) [1] , Chaudhary et al., (2025) [4] , Similarly, other important findings, such as the GCA/SCA variance ratio being less than one for the all fourteen traits, this indicates the predominance of non-additive gene action, which can be effectively exploited in heterosis breeding. Similar findings align with found by Nageshwar et al., (2021) [11] , Ahmad et al., (2024) [1] , Chaudhary et al. (2025) [4] . The general combining ability (GCA) of a parental line arises primarily due to additive gene action and reflects its potential to contribute favorable genes in hybrid combinations. The GCA analysis showed that, among the ten parents evaluated, DBW187, HD2967, Lok-1 and DBW88 were identified as good general combiners for grain yield per plant. In the case of 1000seed weight, the parents Lok-1 (1.9015**), DBW 187 (1.5815**), HD 2967 (1.0368**) and PBW 527 (0.4984*) exhibited significant GCA effects (Table 3). Specific combining ability (SCA) serves as an important criterion for identifying superior parental combinations in crop improvement programs aimed for enhancing yield. A high GCA effect in parents does not necessarily result in high SCA in all hybrid combinations; therefore, the estimation of SCA is essential. SCA refers to the performance of a specific cross that is either superior or inferior relative to its parents. Crosses exhibiting high SCA effects indicate the predominance of nonadditive gene action. the Top three parents in grain yield with the highest GCA estimates were DBW187 (1.1148 **), HD2967 (0.5582**) and Lok-1 (0.5265**) and among the crosses, the top three hybrids in grain yield with the highest SCA estimates were DBW88 x PBW 527 (2.8080 **), PBW 723 x PBW 343 (2.6311**) and DBW 187 x Lok 1 (2.3503) presented in (Table-4.). The SCA estimates for all traits across the 45 crosses further provide valuable interpretations into hybrid performance and gene action.

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