The development of monogerm hybrid sugar beet varieties resistant to diseases and pests, with high root-stem yield and sugar content, depends on the development of cytoplasmic male sterile (CMS) lines with high combinability, maintainers (O-type) and polygerm pollinator lines. The first domestic sugar beet cultivars named Türkseker-1, Türkşeker-poly 861 and Türkseker-poly 863, Anadolumono and Kayamono were developed with the breeding studies started in 1964 at the Sugar Institute. However, over time, domestic varieties could not compete with foreign varieties in terms of yield, quality, resistance to diseases and pests and could not hold on in the market. Sugar beet seed production in Turkey is carried out with the use of mother and father lines supplied from foreign companies on a contractual basis, and Turkey does not have any current domestic varieties. This situation has made our country completely dependent on foreign sugar beet seeds. For this reason, it is important to develop native hybrid monogerm sugar beet varieties that are resistant to diseases with high root-stem yield and sugar content. Erciyes University, Agriculture Faculty and Kayseri Şeker A.Ş. have developed 43 monogerm O-type sugar beet lines and 22 polygerm pollinator lines within the scope of the projects carried out with the support of TÜBİTAK, TAGEM, BAB and Kayseri Şeker Researh and Development center. In order to use these developed O-type lines in the hybrid seed production, CMS equivalents should also be developed. This presented project is a continuation of the previously completed projects and consists of 4 work packages. In the 1. work package of the project, 43 O-type (N)xxzz (repeated parent) lines will be 6 generation backcrossed with a CMS line (S)xxzz (donor parent) to obtain CMS equivalents of O-type lines. In the 2. work package, 18 CMS lines developed within the scope of previously completed projects will be crossed with 22 polygerm pollinators, and 396 monogerm hybrid variety candidates will be developed. In the 3. work package, the 396 hybrid cultivar candidates will be grown for yield and quality test in 4 locations (Kayseri/Develi, Yozgat/Boğazlıyan, Sıvas/Şarkışla and Eskişehir). Compared to the control cultivars, the superior hybrids will be submitted to the registration. In the 4. work package: Among the diseases that cause problems in sugar beet, Cercospora beticola is one of the most common and economically damaging diseases. Since Cercospora leaf spot resistance is controlled by poly genes, a fully resistant cultivar has not been developed yet. Today, sugar beet breeding organizations continue their studies to develop varieties that are super resistant to Cercospora leaf spot disease. In this work package, 21 genotypes resistant to Cercospora leaf spot disease were obtained from the USDA gene bank in 2018 and the seeds were propagated for two years and taken for preliminary testing under field conditions. The reactions of genotypes resistant to Cercospora leaf spot disease will be tested in greenhouse and in-vitro conditions using two isolates with high virulence, and the genotypes most resistant to Cercospora leaf spot disease will be determined. These determined genotypes will be used in breeding programs to develop varieties that are highly resistant to Cercospora leaf spot disease. If the expected goals of the submitted project will be achieved, (a) 43 cytoplasmic male sterile (CMS) lines will be developed to be used in breeding programs, (b) 396 hybrid cultivar candidates will be developed by crossing 18 CMS lines with 22 polygerm pollinator lines. (c) Genotypes will be determined for the purpose of developing varieties that are highly resistant to Cercospora leaf spot disease, which is a major problem in sugar beet production. The production of domestic varieties that will be developed with the following projects that contribute to the national economy by eliminating our dependence on foreign sugar beet cultivars. The development of monogerm hybrid sugar beet varieties resistant to diseases and pests, with high root-stem yield and sugar content, depends on the development of cytoplasmic male sterile (CMS) lines with high combinability, maintainers (O-type) and polygerm pollinator lines. The first domestic sugar beet cultivars named Türkseker-1, Türkşeker-poly 861 and Türkseker-poly 863, Anadolumono and Kayamono were developed with the breeding studies started in 1964 at the Sugar Institute. However, over time, domestic varieties could not compete with foreign varieties in terms of yield, quality, resistance to diseases and pests and could not hold on in the market. Sugar beet seed production in Turkey is carried out with the use of mother and father lines supplied from foreign companies on a contractual basis, and Turkey does not have any current domestic varieties. This situation has made our country completely dependent on foreign sugar beet seeds. For this reason, it is important to develop native hybrid monogerm sugar beet varieties that are resistant to diseases with high root-stem yield and sugar content. Erciyes University, Agriculture Faculty and Kayseri Şeker A.Ş. have developed 43 monogerm O-type sugar beet lines and 22 polygerm pollinator lines within the scope of the projects carried out with the support of TÜBİTAK, TAGEM, BAB and Kayseri Şeker Researh and Development center. In order to use these developed O-type lines in the hybrid seed production, CMS equivalents should also be developed. This presented project is a continuation of the previously completed projects and consists of 4 work packages. In the 1. work package of the project, 43 O-type (N)xxzz (repeated parent) lines will be 6 generation backcrossed with a CMS line (S)xxzz (donor parent) to obtain CMS equivalents of O-type lines. In the 2. work package, 18 CMS lines developed within the scope of previously completed projects will be crossed with 22 polygerm pollinators, and 396 monogerm hybrid variety candidates will be developed. In the 3. work package, the 396 hybrid cultivar candidates will be grown for yield and quality test in 4 locations (Kayseri/Develi, Yozgat/Boğazlıyan, Sıvas/Şarkışla and Eskişehir). Compared to the control cultivars, the superior hybrids will be submitted to the registration. In the 4. work package: Among the diseases that cause problems in sugar beet, Cercospora beticola is one of the most common and economically damaging diseases. Since Cercospora leaf spot resistance is controlled by poly genes, a fully resistant cultivar has not been developed yet. Today, sugar beet breeding organizations continue their studies to develop varieties that are super resistant to Cercospora leaf spot disease. In this work package, 21 genotypes resistant to Cercospora leaf spot disease were obtained from the USDA gene bank in 2018 and the seeds were propagated for two years and taken for preliminary testing under field conditions. The reactions of genotypes resistant to Cercospora leaf spot disease will be tested in greenhouse and in-vitro conditions using two isolates with high virulence, and the genotypes most resistant to Cercospora leaf spot disease will be determined. These determined genotypes will be used in breeding programs to develop varieties that are highly resistant to Cercospora leaf spot disease. If the expected goals of the submitted project will be achieved, (a) 43 cytoplasmic male sterile (CMS) lines will be developed to be used in breeding programs, (b) 396 hybrid cultivar candidates will be developed by crossing 18 CMS lines with 22 polygerm pollinator lines. (c) Genotypes will be determined for the purpose of developing varieties that are highly resistant to Cercospora leaf spot disease, which is a major problem in sugar beet production. The production of domestic varieties that will be developed with the following projects that contribute to the national economy by eliminating our dependence on foreign sugar beet cultivars.