Phenotypic diversity and molecular characterization of male sterility based on cytotype and Ms locus variation in Indian onion germplasm

Abstract

Understanding phenotypic diversity and identifying male-sterile lines in different genetic backgrounds are crucial for onion hybrid breeding. Molecular markers specific to male sterility and pollen viability assist in the accurate identification of male-sterile lines for effective hybrid development. Forty-three onion genotypes were evaluated for agro-morphological variation, pollen viability, and molecular characterization of cytoplasm type and Ms locus. Substantial variability was observed for traits such as bulb weight (30-58.61 g), neck thickness (0.5-1.31 cm), TSS (10-19.6°Brix), days to maturity (125-148), and total yield (94.20-355.22 q/ha). VLRP 39 exhibited the highest yield among all genotypes. Mahalanobis D² and k-means clustering grouped genotypes into two major cluster and three clusters respectively. indicating diverse genetic backgrounds. Molecular analysis using the OSN/Cob marker showed variation in cytoplasm type, 11 genotypes had normal (N), 18 had sterile (S), and 14 genotypes had both N and S types. Genotyping of the Ms locus using the OPT marker identified 31.63% plants as homozygous recessive (msms). Five genotypes VLRP 34, VLYP 2, VLRP 50, VLYP 4, and VLRP 60 contained individual plants with both S(msms) sterile and N(msms) maintainer genetic nature, making them suitable for the development of sterile and maintainer lines. Pollen sterility of plants with S(msms) was also confirmed through evaluation of their pollen viability using acetocarmine staining. This integrated phenotypic and molecular approach provides valuable insights for developing parental lines, especially A and B lines, in onion hybrid breeding programs. It enhances the potential for heterosis exploitation and crop improvement.

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Affiliated Institutions

• Vivekananda Parvatiya Krishi Anusandhan Sansthan IN

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