Wood volume and quality are the most important aspects of commercial forestry production, and studies of wood formation are important in order to increase the value and efficiency of forestry production. The phenylpropanoid pathway produces various compounds with diverse functions both for plant defence against biotic and abiotic stress as well as structural development. One of the main roles is monolignol production for lignin biosynthesis, which is a crucial aspect of wood formation. For this study three candidate genes involved in lignin biosynthesis were selected: phenylalanine ammonialyase (PAL1), cinnamyl alcohol dehydrogenase (CAD) and cinnamoyl-CoA reductase (CCR). Candidate gene expression was analysed in selected individuals with high and low wood density from open-pollinated Scots pine families during early wood (EW) and late wood (LW) formation and correlation between expression of these genes, total lignin content, and wood density was determined. Wood density values for analysed trees were similar within tree families but differed significantly between families with high and low wood density (p=1,06E-20). Wood density was slightly negatively correlated with lignin content (r=-0.36, p=0.038), but only in individuals in the high density wood group. In trees with low wood density, expression of the CAD gene was significantly lower in late wood formation compared to early wood (p=0.00179). In trees with high wood density, expression of the PAL1 gene was five times higher during early wood formation compared to late wood formation. A positive correlation was detected between PAL1 and CCR gene expression during early wood formation (r=0.804) and late wood formation (r=0.466).
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.
Conifer genomes are large and stably diploid, in contrast to angiosperms, which are more variable both in genome size and ploidy. Conifer genomes are characterised by multiple gene families and pseudogenes, contain large inter-gene regions and a considerable proportion of repetitive sequences. All members of plant retrotransposon orders have been identified in gymnosperm genomes, however active elements have not been described. Investigation of transposable elements in Scots pine (Pinus sylvestris L.) could offer insights into transposon-mediated reorganisation under stress conditions in complex and ancient plant genomes. Nine Pinus sylvestris specific markers were developed to hypothetical long terminal repeats (LTRs) from differentially expressed retrotransposon-like fragments after heat stress and insect damage. Genetic diversity of 150 trees from a naturally regenerated pine stand was investigated using the IRAP method. The developed markers revealed high levels of genetic diversity and were able to distinguish subpopulations growing in long-term differential environmental conditions. Somaclonal variation was also investigated using these markers and polymorphic fragments were identified between ramets of Scots pine clones growing in two different plantations, possibly indicating evidence of recent transposition events. Sequencing of the polymorphic fragments identified two groups of sequences containing LTR sequences of an unknown retrotransposon with homology to the LTRs of the Copia-17-PAb-I element.
The development of ecologically adaptable fodder crop varieties is of increasing importance, particularly in the context of climate change. New varieties should be phenotypically and ecologically plastic and able to adapt to differing climactic and soil conditions, ensuring high yields and persistence. Combining Festuca and Lolium species and the development of hybrid (Festulolium) cultivars can be a promising method of combining high yield, high feed quality, persistence, as well as cold, frost and drought tolerance. Breeders at the Institute of Agriculture of Latvia University of Life Sciences and Technologies have been utilizing Festulolium germplasm for several decades. Currently, in cooperation with the molecular genetics laboratory and Latvian gene bank at the Latvian State Forest Research Institute “Silava”, analysis of Festuca, Lolium and their hybrids with DNA markers has been initiated, in order to gain additional knowledge about the breeding material and to increase the efficiency of the breeding process. Results of the assessment of morphological and agronomic traits in long-term field trials are combined with DNA markers analyses in order to determine the correlation of genetic and phenotypic traits.
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.
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.