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Rhizomania and rhizoctonia root rot are both soil-borne diseases of sugar beet. Soil-borne diseases can become an important problem in sugar beet cultivation due to the impossibility of effective control of the pathogen through chemical methods or insufficient efficiency of agronomic practices. Currently, the proper way to control both diseases is using resistant cultivars. In this study, 155 new test-cross hybrids were developed from a cross of 155 inbred lines, bearing dual resistance to both diseases, with a monogerm commercial single-cross. The cross was performed in isolation in 2019 in Karaj. Monogerm hybrids together with one domestic resistant control (Sina cultivar) and four foreign resistant controls (Pirola, Loriquet, Modex, and Novodoro cultivars) were evaluated in augment design in seven regions including Karaj, Mashhad, Shiraz, Miandoab, Khoy, Hamedan, and Kermanshah under infected condition into one or both diseases. Each plot consisted of a line with 8-m-long and each control was repeated five times in the trial. During the growing season, traits such as number of plants per plot, growth uniformity, and intensity of leaf greenness were recorded. At harvest, roots of each plot were counted and weighed and pulp samples were taken to determine the sugar content percentage at the Sugar Technology Laboratory of the SBSI. Then, the sugar yield of the hybrids in each region was calculated, which was the basis for statistical analysis of data in each region as well as combined analysis of all regions. Based on the average of sugar yield, Pirola cultivar with 15 t/ha-1 sugar yield was the best genotype followed by hybrid 35253 (14.82 t/ha-1). The average sugar yield of the domestic control was 11.65 t/ha-1. In total, out of 155 studied hybrids, 33 hybrids did not show a significant difference in terms of sugar yield with Pirola which can be used in following evaluation programs. Key Words: Sugar beet, evaluation, hybrid, augment
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