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Rhizomania and cyst nematode 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, 50 new test-cross hybrids were developed from a cross of 50 inbred lines, bearing dual resistance to both diseases, with a monogerm commercial single-cross and also 40 new test-cross hybrids were developed from a cross of 40 monogerm single-crosses with resistant to rhizomania with a pollinator line with dual resistance. The cross of inbred lines with a single-cross was performed in isolation in 2019 in Karaj and the cross of monogerm single-crosses with a pollinator was done in isolation in Hamedan. Ninety monogerm hybrids together with one domestic resistant control (Shokoufa) and four foreign resistant controls (Saccarra, Cactus, Fernando, and BTS 213) 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, BTS 213 cultivar with 15.17 t/ha-1 sugar yield was the best genotype followed by hybrid 35474 (14.31 t/ha-1). The average sugar yield of the domestic control was 11.90 t/ha-1. In total, out of 90 studied hybrids, 32 hybrids did not show a significant difference in terms of sugar yield with BTS 213 which can be used in following evaluation programs. Key Words: Sugar beet, evaluation, hybrid, augment
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