Fusarium head blight (FHB) is a widespread disease of cereals, including barley (Hordeum vulgare L.), that causes substantial grain yield losses and grain quality deterioration. Resistant varieties provide the greatest potential for reducing FHB. In the present study, we adapted two methods for screening FHB severity using Fusarium culmorum. We used a cut-spike method and a spray inoculation method in the field conditions for screening different spring barley genotypes of Latvian and foreign origin. Screening with the cut-spike method was done for 126 different genotypes in 2008 and in 2009 and for 180 genotypes in 2010. In the years 2011 and 2012, the field inoculation method was used to screen 207 and 164 genotypes, respectively; part of material was tested simultaneously by both methods. A significant effect of genotype was found for both cut-spike and field inoculation methods (p < 0.001); field inoculation method showed a greater proportion of genotype effect and a higher heritability. Using area under the disease progress curve (AUDPC) and score obtained at 26 days after inoculation were equally effective. Correlations between results obtained by both methods in different years were not significant, though, the data of the same year correlated significantly (r = 0.36-0.47, p < 0.05). Results suggest that differences between breeding material can be assessed by both methods; however, the information obtained was contradictory for a number of genotypes. Considering the results and the fact that field inoculation method can more likely provide results of equal value to those in natural conditions in respect to identification of resistant and susceptible genotypes, field inoculation method was recognized as preferable for the assessment of spring barley breeding material. Significant correlation (r = 0.71, p < 0.05) between visual estimate of disease severity and mycotoxin deoxynivalenol (DON) concentration in grain was found in 2011, but in the environmental conditions of 2012 formation of DON was inhibited.

Effect of water level and climatic factors on the radial growth of black alder Black alder (Alnus glutinosa (L.) Gaertn.) is a widespread tree species in Europe and the western part of the temperate climate zone. The area of forest in Latvia dominated by this tree species has substantially decreased due to wide-spread forest drainage. To predict future changes due to environmental change, it is extremely important to understand the function of ecosystems with black alder and their dynamics. Tree rings can be used as a proxy of past environmental factors. The aim of the study was to determine the effects of meteorological and hydrological factors on radial growth of black alder at two study sites (Dursupe and Raķupe) in Latvia. The response of black alder trees to the influence of climatic and hydrological factors was found to depend on site conditions, i.e. a climatic effect was observed in conditions when the water level was low. Spatial variation in the strength of the relationship of black alder growth to temperature, precipitation, and river level suggests that alder growth is more susceptible to drought stress on higher river banks, where the water table is deeper. Black alder trees growing on low river banks can potentially be used to reconstruct past water-levels.

Potato breeding clones were evaluated for resistance to late blight (agent Phytophthora infestans) using tuber inoculation tests and for presence of the resistance alleles of R1 and R3a genes in polymerase chain reaction tests. Among clones tested those expressing high, moderate and low resistance were identified. The data were analysed for the impact of R1 and R3a genes on tuber resistance to late blight in tested plant material. In previous evaluations performed on smaller amount of clones the tuber resistance levels significantly depended on presence/absence of the resistance allele of R3a gene and did not depend on presence of R1 gene allele. In the current study the statistical analyses did not prove the significant difference in resistance levels depending on presence of the resistance alleles, neither of R1 gene, nor of R3a gene. Tuber resistant clones bearing R3a gene resistance alleles still noticeably prevailed over the clones bearing the alleles of R1 gene as well as over the clones bearing the no resistance alleles of both genes. In several cases the resistance of clones with detected resistance allele of R1 gene was higher compared to those derived from the same crosses and showing amplification of the allele of R3a gene or those with no resistance alleles. Clones accumulating the resistance alleles of both (R1 and R3a) genes expressed high tuber resistance accompanied by necrotic reaction.

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