Identification of Owen-Type Male Sterility Maintainers Carrying Resistance Against Rhizoctonia Crown and Root Rot (Rcrr) Disease in Sugar Beet Germplasm

Propagation and maintaining cytoplasmic male-sterile (CMS) lines are prerequisite of hybrid production programs in sugar beet. The identification of Owen-type (O-type) source materials is important to maintain CMS plants that accelerate crosses between single plants. The objectives of the present study were to assess a base beet germplasm (SB19) to identify O-type plants for use in hybrid production programs and test for resistance against rhizoctonia crown and root rot (Rcrr) disease. A family was developed from each two identified candidate monogerm O-types. A number of 100 plants of each family were crossed with FC708 (male sterile) in insulated cages, and the progenies of hybrids were tested for the frequency of male sterility. Progenies of candidate O-types crossed with FC708 revealed various levels of male sterility. Type I and Type II male sterility had lowest frequency, while completely sterile type was the most frequent. The results demonstrated that 6 plants in each family were fully male sterile and their parallels S-1 were selected as O-type and male sterility maintainer. The mean for male sterility frequency was 10.5%. The mean disease index (DI) in the selected O-types was 2.22 that was lower than DI in SB19 as a resistant check. Mean comparison for Rcrr demonstrated that all O-types and SB19 plants were discriminated form Jolgeh as Rcrr-susceptible check. In conclusion, the identified O-types can be tested for combining ability for the development of Rcrr-resistant sugar beet hybrids with respect to root and sugar yield traits.