The onion (Allium cepa. L.) is a biennial vegetable of the daffodil family (Amaryllidaceae L.). Due to its great importance on the world market, more and more scientific studies are being carried out on genetic diversity and the acquisition of varieties resistant to external factors. Using DNA markers, we analysed the genetic diversity of 60 Slovenian onion accessions, each of them represented by four individual plants/genotypes, additionally we included three standards (two commercial varieties and one hybrid). The results of the dominant and codominant genotyping were analysed and presented using different population genetic programmes. A total of 243 genotypes were analysed at 26 DNA loci. First, we performed codominant genotyping with five PCR-specific and trait-linked DNA markers, which successfully distinguished fertile cytoplasm (N) from an autoplasmic mutation on normal cytoplasm (T) and the presence of male sterile cytoplasm in 58 % of the population. In the second group, we performed allelic genotyping with 15 SSR (angl. Simple Sequence Repeats) and 6 ILP (angl. Intron Length Polymorphism) markers and analysed the genetic diversity and variability between and within accessions. The entire accession collection is divided into three groups, with genetic diversity highest within the second group (Fst = 0,16) and lowest within the third group (Fst = 0,12). The AMOVA analysis showed a diversity of 34 % within genotypes, 39 % between them and 27 % between the individual accessions. Using the calculated average Shannon information index (1,370) and expected heterozygosity (0,714), we found that there is high genetic diversity among onion accessions. This is the first onion evaluation of its kind to provide information on the genetic background, degree of relatedness and overall genetic diversity of Slovenian onion accessions.
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