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Evaluation of combining ability and heritability for agronomic traits and seed oil content in rapeseed (Brassica napus L.) cultivars
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Mahtabeh Samadigorji   , Nadali Babaian , Ghafar Kiani , Valiollah Rameeh , Nadali Bagheri |
| University of Agricultural Sciences and Natural Resources , Sari, Iran |
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Abstract: (22 Views) |
Introduction: Rapeseed (Brassica napus L.) is an important oilseed crop with many nutritional, economical, ecological and biological benefits. Combining ability analysis is a valuable approach as it facilitates the identification of the suitable parents for the breeding process. This approach allows plant breeders to exploit heterosis and select the superior crosses for immediate utilization or future breeding programs. To identify suitable parental cultivars and superior hybrid combinations, the estimation of combining ability and heterosis of quantitative and qualitative traits was carried out through one-way diallel crosses in eight rapeseed cultivars.
Materials and Methods: Eight canola cultivars (RGS, Asa, Baharan, Dalgan, Zarfam, Nima, SLM046, and Okapi) were crossed in 2022-2023 growing season as a one-way diallel design. The hybrids of the first generation (F1) along with eight parents (36 genotypes in total) were evaluated using randomized complete block design with three replications in Sari Agricultural Sciences and Natural Resources University, Sari, Iran, in 2023-2024 growing season. The measured traits included days to flowering, days to physiological maturity, plant height, length of the main stem, number of branches.plant-1, number of silique.main stem-1, number of silique.branch-1, silique length, number of seed.silique-1, of 1000- seed weight, seed yield, seed oil and protein content.
Results: Analysis of variance showed that in both general combining ability (GCA) and specific combining ability (SCA) there were significant differences among the parents and hybrids for all studied traits. Therefore, additive and non-additive components play roles in the inheritance of all traits. The results showed that the parents had significant general combining ability in the positive or negative direction for most of traits. In addition, the narrow-sense heritability (h2) ranged from minimum of 0.28 for seed oil content to maximum of 0.49 for days to physiological maturity and main stem length, and the degree of dominance gene effect ranged from minimum of 28.2 for seed oil content to maximum of 0.71 for days to physiological maturity. Positive and significant general combining ability for seed oil content was observed in the cv. RGS (1.39), cv. Asa (2.42), and cv. Okapi (0.57). Also, RGS×Asa (4.68), Asa×Nima (1.6), and Baharan×Zarfam (7.6), with high positive and significant specific combining ability, were identified as superior combinations for this trait. The highest heterosis of the mid parents was observed in Asa×Nima (Ht=8.86) and Nima×SLM046 (Ht=7.96). Nima×SLM046 (Ht=7.73) and Baharan×Zarfam (Ht=6.00) had the highest of heterosis of the superior parent. In addition, Dalgan×Okapi, Asa×SLM046, and Nima×Okapi were found to be suitable combinations for these traits, with significant positive combining ability and high and significant values of heterosis of mid parents and superior parents.
Conclusion: Significant variances of general and special combining ability in all traits showed that both additive and non-additive gene effects played roles in the gene expression of the studied traits. In addition, considering the low narrow-sense heritability and the degree of dominance greater than one for most traits, revealed the greater importance of the non-additive gene effects in controlling these traits.. Therefore, it may not possible to select suitable recombinants in the early generations for the studied traits. To improve these traits in segregating generations, indirect selection of traits that are positively correlated with seed yield should be utilized, and non-additive effects of genes in the occurrence of heterosis can be used for hybrid development. Examination of all crosses in all traits related to seed yield showed that cultivars with high positive general combining ability produced suitable combinations for some traits. Thus, cv. Nima, cv. Okapi and cv. Dalgan, produced suitable crosses in most traits. Also, considering the positive and significant heterosis values in some cross combinations of these cultivars for seed yield and most of the studied traits, it would be poassible to develop cultivars by selecting in the segregating generations. |
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| Keywords: Additive effect, Diallel crosses, Heterosis, Rapeseed and Seed yield |
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Full-Text [PDF 930 kb]
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Type of Study: Scientific & Research |
Subject:
Special
Received: 2025/06/7 | Accepted: 2025/09/5 | Published: 2025/10/27
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Samadigorji M, Babaian N, Kiani G, Rameeh V, Bagheri N. Evaluation of combining ability and heritability for agronomic traits and seed oil content in rapeseed (Brassica napus L.) cultivars. Iranian Journal of Crop Sciences. 2025; 27 (1) :93-109 URL: http://agrobreedjournal.ir/article-1-1421-en.html
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