Microsatellites as a tool for identifying successful pollinators of the pear cultivar ‘Ingeborg’ in Ullensvang, Norway M. Meland 1 , M. Kurtovic 2 , B. Kalamujic 3 , N. Pojskic 3 , L. Lasic 3 and F. Gasi 2 1 Norwegian Institute of Bioeconomy Research (NIBIO), Ullensvang, Norway; 2 Faculty of Agriculture and Food Sciences, University of Sarajevo, Zmaja od Bosne 8, 71 000 Sarajevo, Bosnia and Herzegovina; 3 Laboratory for Molecular Genetics of Natural Resources, Institute for Genetic Engineering and Biotechnology, Zmaja od Bosne 8, Kampus, 71 000, Sarajevo, Bosnia and Herzegovina. Abstract Due to their Mendelian inheritance, microsatellites or SSRs (simple sequence repeats) can readily be used for parentage analyses of pear seedlings, thus revealing the female and male parents of the plant. However, in cases where obtained pear seeds display low viability, conducting a parentage analyses on the pear seeds themselves could be used in order to identify the male parent (successful pollinator). In this study, batches of seeds were extracted from fruits of the triploid ‘Ingeborg’ pear (‘Conference’ × ‘Bonne Louise’), the main commercial pear cultivar in Norway. Mature pears were collected from eight commercial pear orchards located in Ullensvang, at 60° North and seeds were collected. Genomic DNA was subsequently isolated from the obtained seed batches and genotyped using 12 microsatellite markers. The same markers were also used for the genetic characterization of ‘Ingeborg’ and five pear genotypes used as pollinators in the sampled orchards (‘Clara Frijs’, ‘Herzogine Elsa’, ‘Anna’, ‘Colorée de Juillet’ and ‘Belle lucrative’). The obtained SSR profiles were used in paternity analyses, as well as for gene assignment analyses. Both approaches identified pear ‘Clara Frijs’ to be the most successful pollinator in most of the sampled orchards. Subsequent S allele genotyping of ‘Ingeborg’ and five pear genotypes used as pollinators in the sampled orchards revealed that the preferential pollination by individual genotypes was not caused by gametophytic incompatibility or semi-compatibility. Keywords: Pyrus communis L., pear seeds, gene assignment analyses, gametophytic incompatibility INTRODUCTION ‘Ingeborg’ pear (‘Conference’ × ‘Bonne Louise’) currently represents the main commercial pear variety grown in Norway. ‘Ingeborg’ is a triploid, which probably derived as a result of the fertilization of an unreduced egg cell from ‘Conference’ by a haploid pollen cell from ‘Bonne Louise’ (Sehic et al., 2012). Although ‘Ingeborg’ possesses good pomological traits, the fruit set and subsequent yields of this cultivar have proven to be significantly lower compared to other pears grown in Norway (Meland et al., 2017). Pear seeds found in ‘Ingeborg’ fruits are frequently underdeveloped, indicating that a significant cause behind the low fruit set could be related to inadequate pollination and fertilization. Considering the low and variable fruit set in ‘Ingeborg’ pear, currently cultivated in and around Ullensvang, Norway, it would be of a particular importance to identify which one of the used pollinator cultivars is the most effective. Microsatellite markers or SSRs (simple sequence repeats) have proved efficient in parent-offspring analyses on pear (Kimura et al., 2003). Therefore, in this study microsatellite markers were used as a tool for identifying successful pollinators of ‘Ingeborg’ pear. Additionally, S allele genotyping of ‘Ingeborg’ and five pear genotypes used as pollinators was conducted in order to examine if the preferential pollination by individual pollinator is caused by sexual incompatibility. Acta Hortic. 1229. ISHS 2018. DOI 10.17660/ActaHortic.2018.1229.9 Proc. Int. Symp. on Flowering, Fruit Set and Alternate Bearing Eds.: F.P. Marra, T. Caruso and S.K. Mitra 57