The impact of climatic and genetic factors on needle cast damage, as well as relationship between the degree of damage and survival and growth of trees was evaluated in the study. The analysis was done in two series of experiments, both established in two locations in Latvia (central and eastern part). Needle cast damage (in 5 grade scale) as well as the height and height increment, diameter of root collar and survival of trees were assessed. Results suggest that the degree of needle cast damage was influenced by the genetic, as well as climatic factors, and also their interaction. The average degree of needle cast damage in experiment of open-pollinated families was 4.7 ± 0.01 in central and 4.6 ± 0.03 in eastern Latvia; in the experiment of control-crossed families it was 4.6 ± 0.02 in central and 3.4 ± 0.04 in eastern Latvia. The impact of genetics on the needle cast damage degree was statistically significant (p is less than 0.05), and this effect was observed when any of growth traits (diameter, height or height increment) was used as a covariate in analysis. Results suggest the potential to select more resistant families, since the genetic correlation of grade of the damage between locations was significant (r = 0.40 - 0.72) and therefore improve also the growth of trees, since the grade of the damage had a negative correlation with growth traits both at provenance and family mean level (r = -0.69 and r = -0.42; p is less than 0.01).

Recent studies have demonstrated the occurrence of different needle cast (Lophodermium spp.) species in young Scots pine Pinus sylvestris L. stands in different regions of Latvia. The impact of these fungi has been known also historically, but is predicted to increase in future due to climate changes that are forecasted to have a positive impact on presence and vigour of various species of fungi. The aim of the study was to characterize the needle cast damage in young Scots pine stands in central Latvia. Material was collected in 12 Scots pine stands at the age of 3 to 26 years in 28 plots with a total area of 8.1 ha in the middle of two consecutive growing seasons (years 2012 and 2013). The impact of disease was visually assessed using a 5 grade scale, depending on the proportion of damaged (brown) one-year old needles. Incidence of damaged trees (P, %) and damage intensity (R, %) was calculated and used to characterize the occurrence and severity of the infection in the stands as well as its link to other stand parameters. Damage incidence (ranging from 20 to 100%), as well as the intensity (from 4 to 35%) was slightly (incidence-also significantly) higher in 2013 in comparison to 2012; correlation between those two parameters was strong in both years (r = 0.94 and r = 0.84, respectively). The stand age, density (ranging from 1200 to 6900 trees haE-1) and tree height did not significantly correlate with the damage incidence or intensity. Forest type (Hylocomiosa or Myrtillosa mel.) was not a significant factor, too.

European pear scab (Venturia pyrina Aderh.) is common and economically important disease in commercial orchards in most of the pear (Pyrus communis L.) growing areas worldwide. Studies on pear scab pathogen V. pyrina diversity in general and among different geographical regions are scars at an early stage. In the limited number of studies reported so far, some attempts have been made to characterize and define races or biotypes of V. pyrina and new biotypes co-adapteted to specific cultivars have been recorded recently. Despite the long history, worldwide distribution and increasing economic significance of the European pear scab, the research on control methods, and pathogen biology and disease epidemiology that could aid to develop more effective and also alternative to fungicide application control methods are still limited. Mechanisms of European pear resistance to scab remains uncertain and currently only one major resistance gene Rvp1 has been identified and characterised. Although the disease is important in many European countries, breeding programs of pear scab-resistant varieties are still under development. In this paper we provide an overview on V. pyrina, its significance and distribution, control methods and current scientific progress in understanding of the pathogen and the disease. Overview of literature on V. pyrina characterization, ecology, biology and diseases epidemiology from Latvia and other countries has been used for the study.

Woody plants at urban greeneries in Lithuania are injured by rust fungi of 13 genera, 28 species: Coleosporium pulsatillae, C. tussilaginis, Cronartium flaccidum, C. ribicola, Cumminsiella mirabilissima, Gymnosporangium clavariiforme, G. confusum, G. cornutum, G. sabinae, G. tremelloides, Hyalopsora aspidiotus, M. allii-fragilis, M. allii-populina, M. caprearum, M. epitea, M. laricis-populina, M. populnea, Melampsora ribesii-viminalis, M. salicis-albae, Melampsorella caryophyllacearum, Melampsoridium betulinum, M. carpini, Ochropsora ariae, Phragmidium tuberculatum, Pucciniastrum areolatum, P. symphyti, Uromyces caraganicola, U. pisi-sativi. During 2009 – 2017 Gymnosporangium sabine had the strongest damages (from 0.21 ± 0.00 to 2.43 ± 0.33 grades) on Pyrus pyreaster, the weakest damages had done G. cornutum on Sorbus intermedia and S. x thuringiaca ‘Fastigiata’ – 0 – 1 ± 0.58 grades.

Rhododendron spp. plants were surveyed for Phytophthora infection in Lithuania during 2010 – 2016. This study aims to identify Phytophthora genus pathogen which infects rhododendrons in Lithuania. Samples were taken from young sick plants with visible infection symptoms. Soil sampling was performed from the rhizosphere of sick plants. DNA from soil and plant was tested for the presence of Phytophthora genus pathogens. Data showed positive results of Phytophthora genus specific probe during real-time PCR. All tested diseased leaves and soil samples have indicated Phytophthora sp. infection during Alert-LF® Phytophthora spp. analysis. The extracted DNA concentrations were not very high for Phytophthora species identification, but in most cases, it was high enough for further researches.

Yellow rust caused by Puccinia striiformis is a significant wheat disease in cereal growing areas worldwide. On average, yellow rust can cause 50% big yield damages resulting in economic losses. Yellow rust damages wheat leaves, leaf sheaths, awns, and glumes. Puccinia striiformis is divided into four lineages – P. striiformis sensu stricto, P. pseudostriiformis, P. striiformoides, P. gansensis. Different races of yellow rust have been determined. After 2000 three new aggressive races – ‘Warrior’, ‘Kranich’ and ‘Triticale aggressive’ have been identified. New races are characterized by shorter latent period, extended spore germination and tolerance to a high temperature in comparison with the races determined before 2000. These characteristics allowed the new races to replace races dominant before 2000. Yellow rust is a biotrophic heteroecious fungus with a complicated life cycle. For successful development, Puccinia striiformis requires cereals as primary hosts and Berberis spp. as alternate hosts. The history of studies regarding yellow rust is more than two hundred years old but only in 2010 the ecidiospores of yellow rust were found on the alternate host Berberis spp. Two types of resistance – seedling (or all-stage) resistance and adult plant resistance (APR) were discovered. Since 2000 multiple severe epidemics of yellow rust have been observed in cereal growing areas with warmer climate. In recent years, the incidence of yellow rust in Latvia has increased. Particular studies about the biology, distribution, and races of Puccinia striiformis in Latvia are necessary. This article summarizes the information about the classification, biology and harmfulness of the yellow rust.

Brown rust caused by Puccinia recondita is a significant disease in cereal growing areas worldwide. On average, brown rust can cause yield losses from 10% to 40% resulting in economic losses. The disease damages the leaves, stems and glumes of cereals. Classification of the pathogen causing brown rust has undergone several revisions. There are two different opinions about the causal agent causing brown rust on rye and wheat. Some scientists consider that the causal agent of brown rust in wheat (Triticum aestivum L.) and rye (Secale cereale) is included in the broad species of P. recondita defined by Cummins, but other scientists consider that there are two species causing brown rust – P. recondita in rye and P. triticina in wheat. There are many studies about the races of P. recondita in wheat: in North America, 70 races are collected every year; in Canada, 35 races have been found; in Europe, 105 races have been found. Unfortunately, there are no studies about the races of the pathogen of rye. P. recondita is a heteroecious fungus with a complicated life cycle. For successful development, the fungus requires cereals as primary hosts and different alternative hosts, depending on the specialization of the pathogen. Specific studies about the biology, distribution and harmfulness of Puccinia recondita in Latvia are necessary. Monographic method was used for this study. The aim of this article is to summarize the information from the literature about Puccinia recondita, the causal agent of brown rust, with emphasis on the occurrence, harmfulness, taxonomy, and life cycle of P. recondita f. sp. secalis.

Japanese quince (Chaenomeles japonica) is cultivated as a fruit crop because its fruit possesses valuable properties. The total area of Japanese quince in Latvia is continuously increasing; therefore, fruit rot can become an important reason of yield loss. The aim of this study was to clarify the fruit rot incidence in Japanese quince plantations in Latvia and explore the influencing factors of rot development in the year 2017. The evaluation of fruit rot was carried out during the fruit development in eight places of different regions of Latvia where Japanese quince is grown commercially. Three plantations of different Japanese quince cultivars in Dobele and seven plantations where Japanese quince is grown from seedlings were observed. Fruit rot incidence among plantations had no significant differences. Statistically significant differences in fruit rot incidence depending on quince growth stage (p is less than 0.05) were found. Significant differences in fruit rot incidence were found between cultivars in Dobele.

Healthy seeds are essential for the optimal plant population and yield, but seed-borne pathogens, such as Fusarium spp., may reduce seed germination, quality and cause damping-off of the seedlings. Fusarium graminearum is a dominant pathogen of cereal crops and can cause significant losses of grain yield and quality. It is important to evaluate the role of alternative inoculum source in crop rotation. The aim of this study was to assess the impact of F. graminearum infection on different plant seed germination and seed infestation. The research was conducted at the Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, in 2017. Visually healthy seeds of bean (Vicia faba L.), pea (Pisum sativum L.), lupine (Lupinus angustifolius L.), soybean (Glycine max. (L.) Merr.), lucerne (Medicago sativa L.), white (Trifolium repens L.) and red (Trifolium pratense L.) clover were inoculated with 10 mL of F. graminearum suspension, adjusted to 1×106 conidia per mL. Seed infection was counted 2 and 6 days after inoculation (DAI), seed germination energy and reduction rate – after 3 DAI and germination index – 6 DAI. Results showed that all inoculated seeds were covered with typical to F. graminearum red-purple mycelium. The results of inoculated seeds with F. graminearum showed red-purple mycelium growth on the seeds (infection from 21.25 up to 100%). The results showed that germination energy decreased on pea (2.56%) and lupine (7.79%) seeds. Our results suggest that various plant seeds differently react to F. graminearum infection. The highest infection of F. graminearum was obtained on pea, lupine seeds and the least on red clover.

Problems in hulless barley growing are caused by a low germination ability and emergence. Grain quality for feed and food are influenced by threshability and infection with fungal diseases. The aim of experiments was to investigate the possible hulless barley seed and grain quality problems under Latvia's conditions. Germination, emergence, test weight, 1000 grain weight and threshability of 77 hulless barley genotypes of diverse origin were determined and compared to hulled control varieties. Correlation between hulless barley germination, grain germ damage and grain infection with Fusarium, Helmintosporium and Penicillum was analyzed. The seed material structure (content of grains with damaged germ, broken grains and grains with undetached hulls) of 5 hulless barley genotypes was determined.