In order to best conserve, as well as utilize, traditional apple germplasm in Norway, an apple heritage cultivar collection was established in Ullensvang, western Norway, which aims to become the National Clonal Germplasm Repository. The establishment of the apple heritage cultivar collection was preceded by a molecular study that aimed to genotype a large number of apple accessions maintained in various ex situ sites in western and south-eastern Norway, using a rather small set of eight SSR markers. However limited, the marker set managed to identify synonyms, homonyms, and duplicates within and among the investigated collections. In this study, 171 apple accessions from the Ullensvang apple heritage cultivar collection were genotyped using a set of 20 different SSR markers. Approximately half of the accessions have been previously genotyped using eight SSR markers, enabling an assessment of whether the use of a larger marker set would yield a more accurate characterization. Based on the obtained molecular data, the apple heritage cultivar collection was determined to hold a key part of the overall genetic diversity of the Norwegian apple germplasm. Furthermore, the twelve additional SSR markers were able to differentiate several accessions groups originally thought to be synonyms, as well as to provide a more detailed insight into the genetic structure of this germplasm.

In order to fill in a decade-long information gap regarding the biological, serological and molecular data for plum tree viruses in Bosnia and Herzegovina, a three-phase study combining symptom evaluation, and serological and molecular assays with high-throughput sequencing (HTS) technology was conducted. The most frequently observed symptoms were discolorations in the form of ring patterns, bands and irregular shapes, as well as vein banding. Sharka-associated symptoms in the form of ring patterns and semicircles were prevalent. A total of 468 plum tree samples were tested by ELISA for the presence of PPV, ApMV, PDV, PNRSV, PBNSPaV, ACLSV and MLRSV. An overall infection incidence of 51.9% was detected, with PPV being the most prevalent (48.7%), followed by PDV (2.99%), PNRSV (0.21%) and mixed infections of PPV+PDV (1.71%). RT-PCR-assisted strain typing in 45 samples revealed PPV-D as the most common strain (22.22%), followed by PPV-REC (6.66%). Mixed infections of PPV-D+PPV-REC were detected (6.66%). HTS enabled the recovery of a 9743 nts long sequence of PPV-D (PPV_O7/80, MW412433), which shared the highest nucleotide and amino acid identities with isolates S13 (LC375131) from Serbia, SVN1 (LC375132) from Slovenia and N9 (LC375129) from Bulgaria. The phylogenetic analysis of the whole genome placed the isolate of the D strain in a distinctive group with the Slovenian isolate SVN1 (LC375132). In addition, the (Cter)NIb/(Nter)CP fragment of a PPV-REC isolate (MW412434) obtained in this survey formed a separate group with previously known isolates from Bosnia and Herzegovina (BOS64Pl and BOS257Pl).

Apple accessions, currently maintained within the two main ex situ collections in Bosnia and Herzegovina (B&H), have previously been genotyped using microsatellite markers. The obtained molecular data provided insight into mislabeled accessions and redundancies, as well as the overall genetic structure of the germplasm. The available dataset enabled the creation of a core collection consisting of 52 accessions. The reliability and usefulness of microsatellites has made this low-density marker system a norm in studies on apple germplasm. However, the increased access to medium- and high-density SNP arrays, developed specifically for apples, has opened new avenues of research into apple genetic resources. In this study, 45 apple genotypes consisting of 33 diploid core collection accessions from B&H and 12 international reference cultivars were genotyped using an Axiom® Apple 480 K SNP array in order to examine their genetic relationships, population structure and diversity, as well as to compare the obtained results with those calculated on previously reported SSR profiles. The SNPs displayed a better ability to differentiate apple accessions based on their origin, as well as to cluster them according to their pedigree. Calculating identity by descent revealed 16 pairings with first-degree relationships and uncovered the introgression of ‘Delicious’ and ‘Golden Delicious’ into the core collection.