Cytoplasmic Male Sterility in Sugar Beet: Mitochondrial Minisatellite and Chloroplast CAPS Markers and Field Phenotype Stability Study

Cytoplasmic male sterility (CMS) is a key cornerstone of hybrid breeding in sugar beet (Beta vulgaris L.). Reliable identification of cytoplasmic types and evaluation of their phenotypic stability are therefore important for the effective use of CMS in breeding programs. The aim of this study was to comprehensively characterize 30 sugar beet breeding lines of different origins using molecular and phenotypic approaches. Mitochondrial minisatellite markers TR1–TR3 and the CAPS marker in chloroplast region petG-psbE were employed, together with evaluation of phenotypes for anther morphology and pollen fertility over three years under the conditions of southeastern Kazakhstan. Based on the molecular analysis, most CMS breeding lines were classified as carriers of mitotype min04, the O-type control lines with mitotype min18, and alloplasmic breeding lines with min06, which indicated the presence of an alternative origin of CMS. Combined analysis of mitochondrial and chloroplast markers revealed cytoplasm heterogeneity in several accessions, confirming the need for individual molecular control during the maintenance of CMS breeding lines. The evaluation of phenotypes over three years demonstrated that anther dehiscence and pollen fertility varied significantly depending on hydrothermal conditions. Combining molecular study with multi-year evaluations of phenotypes enables reliable cytoplasm type identification, cryptic heterogeneity detection, and the selection of breeding lines with stable male sterility for breeding of sugar beet hybrids.