Seed of hybrid onion (Allium cepa L.) is produced using cytoplasmic male sterility (CMS). For the most widely used source of onion CMS, male sterility is conditioned by the interaction of male sterile (S) cytoplasm and the homozygous recessive genotype at the nuclear male fertility locus Ms. Because of the biennial generation time of onion, classical crossing and segregation analyses take years to establish cytoplasms and genotypes at Ms. Numerous molecular markers have been developed to distinguish onion cytoplasms and estimate genotypes at Ms. Two nuclear markers (jnurf13 and AcPms1) have been reported to cosegregate with Ms and correctly predict genotypes in commercial breeding lines and diverse onion germplasm; however, these markers were less predictive for open-pollinated (OP) populations from India. We evaluated the efficacy of jnurf13 and AcPms1 to correctly classify genotypes at Ms using 144 random plants from three OP populations of long-day onion from North America. No recombination events were detected between AcPms1 and the Ms locus and three events occurred between jnurf13 and Ms. Our results support either marker as a useful tool to predict genotypes at Ms in North American populations of onion, with AcPms1 being the better of the two.
Michael J. Havey and Christopher von Kohn
Chandra S. Thammina, Christopher von Kohn and Margaret R. Pooler
The genus Magnolia (Magnoliaceae) comprises more than 130 species distributed predominantly in temperate and tropical regions in Southeast Asia and is valued worldwide for its ornamental traits as well as for timber and medicinal products, and in trade. Despite their favored status, many species of Magnolia are faced with threats from logging, agricultural land use, development, and collection, and are at risk of extinction. Conservation of these species through habitat preservation and in ex situ collections is needed to prevent extinction. To provide a tool for conservation of Magnolia species, microsatellite markers developed previously for Magnolia ashei were tested in 10 other species of Magnolia to determine their transferability across species. Of the 64 primer pairs tested, 21 amplified alleles in the expected size range in all samples; 11 primer pairs amplified clean products in most, but not all, species; 18 primer pairs consistently amplified a polymerase chain reaction (PCR) product in most species, but had either low peak height or other amplification issues; and 14 primers showed excessive stutter, nonspecific amplification, or no amplification. Cluster analysis using the 129 alleles amplified by these 21 simple sequence repeat (SSR) primer pairs generated groups that corresponded to the known taxonomic relationships in this genus.