Background: The cytoplasmic-genic male-sterility system has been extensively employed for the production of onion hybrids. Molecular marker-assisted characterization of the cytotypes and genotyping at the restorer-of male-fertility (Ms) locus is important for the accelerated breeding of onion hybrids. Indian onion breeding has focussed more on open-pollinated varieties than hybrids. To accelerate the breeding efforts, marker-assisted selection (MAS) plays a pivotal role.
Methods and results: This study aimed to characterize the Indian breeding lines, varieties, hybrids, and exotic accessions for cytotype and Ms locus. For cytoplasm, cytotype markers, accD, and MKFR and for Ms locus identification, PCR markers AcPMS1 and AcSKP1 were employed. Bulk strategy to identify cytoplasm and Ms locus was tested. Sequencing of PCR products amplified by accD was also tried. Both the accD and MKFR were synonymous in cytoplasm identification except in T821 where T cytoplasm was identified. AcPMS1 was more reliable than AcSKP1 for Ms locus identification. Sequencing proved that N and T cytoplasm are identical. Bulking strategy can be used for cytotype identification but not for Ms locus.
Conclusions: Indian onions have a predominance of normal (N) cytoplasm and homozygous recessive (msms) locus. This might be beneficial for hybrid development. S cytoplasm was identified in exotic varieties. For the first time, T cytoplasm has been reported from India. These findings will assist Indian onion breeders to develop MAS strategies for accelerating hybrid development programs. And for the release of onion hybrids with high productivity and uniformity.
Keywords: Cytoplasmic male-sterility; Heterosis; Onion. Allium cepa; Restoration of male fertility.
© 2022. The Author(s), under exclusive licence to Springer Nature B.V.