Common ash (Fraxinus excelsior L.) has a widespread distribution throughout Europe, and Latvia is almost at the north eastern edge of the distribution range. In Europe, ash is threatened by ash dieback, a disease caused by the introduced ascomycete Hymenoscyphus fraxineus. Chloroplast and nuclear DNA markers have been used to study the genetic diversity and population structure of ash both in a broader pan-European context as well as in more restricted regions. Some of the markers analysed in these previously published reports were also utilised in this study, enabling comparisons of the genetic parameters calculated from the nuclear SSR marker data and of the haplotypes identified with the chloroplast markers. Analysis of chloroplast markers revealed one dominant haplotype in Latvian stands, which corresponds to the haplotype previously found in Eastern Europe and Scandinavia. A second haplotype, corresponding to a previously reported central European haplotype was found in all individuals from the Ķemeri stand, indicating that this stand was naturally established from introduced germplasm, which was planted in a neighbouring park. The nuclear SSR markers revealed low levels of differentiation of Latvian F. excelsior stands, probably due efficient pollen flow between stands. The analysis of both chloroplast and nuclear DNA markers has revealed different aspects of the structure and provenance of Latvian F. excelsior populations.
Use of DNA markers for cereal line uniformity assessment
Prior to the registration of a new variety, it is required to undergo Distinctness, Uniformity and Stability (DUS) testing. Preparing a newly developed variety to meet the requirements of DUS testing is a lengthy process, particularly regarding aspects of uniformity and stability. Field testing of a large number of lines is time and resource intensive. In addition, the expression of certain traits may be influenced by environmental conditions. The use of DNA markers may allow rapid assessment of the level of genetic diversity within a particular line or variety, and to remove individuals that are genetically differentiated, thus accelerating the homogenisation of a newly developed variety. In this study, we utilised AFLP and the iPBS marker techniques to assess genetic variation within advanced breeding lines of several cereal species (triticale, wheat, barley). The combined use of molecular and morphological selection over three years of analysis and selection resulted in the reduction of genetic diversity within breeding lines.
Rye (Secale cereale L.) is an important grain crop in Latvia, where it is mainly used for baking rye bread, which is a popular staple. However, the area under rye cultivation in Latvia is small, and the majority of varieties planted are foreign. In 1937, almost 290 000 ha of rye were planted, while in 2011, only 28 000 ha were planted, or ~5% of the area planted with cereals. The Latvian rye genetic resources collection contains nine accessions, including old and new cultivars, landraces and one repatriated accession, which was previously held in the N. I. Vavilov Research Institute of Plant Industry collection. A set of descriptors has been developed for rye, and field evaluations of the Latvian rye collection have been started. A set of simple sequence repeat (SSR) markers has been utilised for genetic fingerprinting of the collection. The initial genetic results indicate that the Latvian rye collection contains a high degree of genetic diversity. Analyses are continuing in order to more fully characterise the collection both phenotypically and genetically.