Sugar beet (Beta vulgaris L.) is one of the most important sugar crops and potential energy crops in China. The utilization of its heterosis is crucial for breaking through the bottlenecks in yield and quality, while the fertility identification of binary male-sterile lines is the core link to ensure the purity of hybrid seeds. Due to its indeterminate inflorescence, artificial emasculation of sugar beet is not feasible, which significantly increases the difficulty in hybrid seed production. To rapidly and accurately identify the fertility composition of monogerm binary male-sterile lines of sugar beet, ensure the maternal line purity in sugar beet hybrid seed production, and improve breeding efficiency, this study conducted fertility identification using molecular marker technology with 7 monogerm binary male-sterile line germplasm resources (297 plants) provided by three research institutions in different regions of China. Genomic DNA was extracted from young sugar beet leaves by the CTAB method. The cytoplasmic fertility types were identified using the TR1 primer, and the fertility gene composition at the nuclear Rf1 locus was verified by the s17 molecular marker combined with Hap II and Hind III double digestion. The results showed that in the cytoplasmic fertility identification, the proportion of S-type cytoplasm in Lines 2 to 7 reached 100%, indicating stable sterility without maintainer line contamination; Line 1 had 93.33% S-type cytoplasm, mixed with 6.67% N-type cytoplasm. For the nuclear Rf1 locus identification, 93.27% (277 plants) of the tested materials yielded the target 1800 bp band by PCR amplification, which were preliminarily identified as homozygous recessive type. Among them, Lines 1 to 3 all showed a single 1800 bp band pattern, indicating homozygous and consistent nuclear fertility genotypes; 20 plants (6.73%) in Lines 4 to 7 exhibited a composite 1800/1300 bp band pattern, suggesting the presence of restorer allele contamination in some lines. Genotype analysis based on 35 enzyme-digested verification samples revealed that the 4/4 genotype had the highest proportion. This study realized the rapid and accurate identification of cytoplasmic and nuclear fertility in monogerm binary male-sterile lines of sugar beet through molecular marker technology, clarified the fertility purity status of 7 germplasm resources, and verified the application value of this technology in the fertility identification of sugar beet binary male-sterile lines. These results provide a scientific basis and technical support for controlling maternal line purity and improving breeding efficiency in sugar beet hybrid seed production.
Song et al. (Sun,) studied this question.