Eight rice genotypes, including Binam, Hashemi, Deylamani, TH1, Hasani, Saleh, IR75479-199-3-3, and Gohar, were crossed in a line tester mating design to generate breeding populations, assess the general and specific combining ability (GCA and SCA) and identify suitable combinations for yield. 23 genotypes (15 F1s and eight parents) were evaluated in a randomized complete block design with three replications at the Rice Research Institute of Iran during the 2020 cropping season. Analysis of variance revealed significant genotype effects and GCA and SCA mean square values for all the investigated traits, which indicated the genetic diversity of the parental genotypes and the importance of both additive and non-additive gene effects in the inheritance of the studied traits. Results indicated that additive gene action controlled plant height. Meanwhile, non-additive gene action controlled panicle length, number of panicles per plant, heading date, hundred-grain weight, number of grains per panicle, and grain yield. Effects of general combining ability were significant for the panicle length, the number of panicles per plant, heading date, hundred-grain weight, number of grains per panicle, and plant height in all testers. Hasani and Saleh's genotypes demonstrated to be good general combiners for early maturity. Gohar was the best specific combiner to enhance yield components. Hashemi×Gohar was identified as the best combination for improving grain yield and reducing the number of days to heading. The predominance of non-additive types of gene actions related to grain yield and its components suggested that selecting the best plants should be postponed to advanced generation.
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Rice is one of the most important sources of energy for Iranians. Currently, approximately four million tons of paddy are produced annually in 19 provinces of the country. More than 50 new rice cultivars have been introduced in Iran over the last 60 years. The average yield of rice in these years has increased from 2 t ha‒1 to nearly 5 t ha‒1 in farmers’ paddies, although some improved cultivars can produce up to 9 t ha‒1. The main strategy of rice breeding in Iran during the first 40 years was purifying local populations, introducing foreign lines, and producing high-yielding cultivars by cross-breeding and mutagenesis. Meanwhile, the production of high-quality cultivars from crosses between local varieties and high-yielding cultivars has been more emphasized recently. In this review, along with introducing improved varieties of Iranian rice and their characteristics, different improvement methods for creating these varieties are mentioned. Along with traditional breeding methods, it seems that Marker-assisted breeding and breeding by rational design can play important roles in the future of rice breeding in Iran.
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