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The creation of synthetic varieties, especially in plants where hybrid seed production is not possible, is one of the most important methods of plant breeding for forage crops. Since Pearl millet is a cross-pollinated plant with high heterosis, it is possible to successfully utilize heterosis in this plant through the creation of synthetic varieties. To develop a synthetic variety of pearl millet, five high general combining ability pearl millet lines from previous year's experiments were crossed in a polycross nursery in all possible directions using 3×3, 4×4, and 5×5 Latin square designs, forming three, four, and five-parent crosses, respectively. Each experimental unit consisted of a 5-meter row with 60 cm row spacing. Throughout the growing season, all agronomic practices such as fertilization, irrigation, etc., were carried out according to local farming norms. After pollination, to prevent bird damage, all panicles were covered with bags, and at the end of the growing season, seeds from the non-sibling families derived from the polycross nursery were collected. In the following year, an equal amount of seeds from each line in different replications was mixed together to form the syn1 generation. In the second year, the first generation of synthetic varieties was planted in isolation (at least 400 meters away from each other and other pearl millet fields) and pollinated freely, resulting in the production of the second synthetic generation seeds, syn2. n the third year, the first and second generations of synthetic varieties (three, four, and five-parent varieties), along with the Mehran variety as a control, were planted in a randomized complete block design with four replications in Karaj, Isfahan, Birjand, and Zabol, based on the region's climate and at the appropriate planting time. Each experimental unit consisted of four rows, each 5 meters long, with a row spacing of 60 cm. Trait recording was done according to the ICARDA guidelines, using the two middle rows. To assess traits such as the number of days to 50% flowering, plant height, stem diameter, panicle length, panicle diameter, and the number of tillers per plant, random samples from the plots were selected, and trait data was recorded based on the average of ten plants. To assess forage performance, the two middle rows from each replication were harvested at flowering time and weighed. The raw data were statistically analyzed using SAS software, and mean comparisons were made using Duncan's multiple range test. The results showed that the main effect of genotype was significant for all traits except for the number of days to flowering and the number of tillers. Overall, the results of this experiment indicated that synthetic varieties showed a good relative superiority in terms of yield and other agronomic traits compared to open-pollinated varieties. Additionally, the second generation of synthetic varieties, regardless of the number of parents, had lower yield compared to the first generation.
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