Identification of two SCAR markers co-segregated with the dominant Ms and recessive ms alleles in onion (Allium cepa L.)

Cytoplasmic genetic male-sterility is used to produce hybrid onion (Allium cepa L.) seeds worldwide. In this paper, we present the results of research aimed toward identifying PCR-based markers linked to the Ms locus through amplified fragment length polymorphism (AFLP). After screening 512 AFLP primer combinations, only one AFLP fragment was identified as being flanking linked to the dominant Ms allele. Subsequently, the AFLP marker was converted into a sequence-characterized amplified region (SCAR) marker, designated as DNF-566, co-segregated with the dominant Ms allele in first backcross (BC₁) segregated populations. Furthermore, we designed another molecular marker (RNS-357) co-segregated with the ms allele to identify different genotypes (i.e., MsMs, Msms, or msms). Both markers could be used for evaluating onion lines with different genetic backgrounds (including male-sterile lines, maintainer lines, male-fertile lines, and commercial based F₁ hybrid cultivars). The results of this study indicate that maintainer plants could be directly selected by using these 2 SCAR markers in the onion breeding process, and this may contribute significantly toward breeding onion F₁ hybrid cultivars.