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Sea buckthorn (Hippophae rhamnoides L.) is a native species in various regions of Asia and Europe. It is cultivated as a multipurpose horticultural species for food, pharmacology, cosmetics, and environmental conservation. Diseases in natural populations and managed landscapes have increased, endangering sea buckthorn growth and cultivation worldwide. Sea buckthorn diseases caused by pathogenic fungi are widespread but still poorly studied. In the previous studies, commercial orchards and wild habitats in Latvia had been surveyed, and a fungal collection isolated from branches, roots, and trunks with various disease symptoms was established. In order to explain the role of several pathogenic fungi in causing sea buckthorn diseases, the revision of the collection was made, and the analysis of the identified species complex in relation to host plant symptoms was carried out. The isolated fungi were identified based on morphological characters and analysis of ITS/5.8S sequences. The most often reported symptoms were dead buds and leaves, cankers and cracks on trunks and main branches, and necrosis of various tissues on branches and roots, resulting in the death of the shrubs. The analysis of the observed symptoms and the isolated pathogenic fungal species indicates that sea buckthorn diseases are often of a complex nature, and it is necessary to explain the effect of each species on the plant, including complex infections. In-depth studies on the interaction of the potentially most important pathogenic fungal species (e.g. Hymenopleella hippophaeicola, Eutypa spp.) with sea buckthorn were initiated by conducting bioassays under controlled conditions on different cultivars. [ABSTRACT FROM AUTHOR]

Fruit growing is an important niche in the structure of agriculture. Apple and pear are the most widely grown and economically significant fruit crops in the world and in Latvia, while the scab caused by Venturia inaequalis and V. pyrina are the most important diseases for these species. Considering environmental and food safety concerns, the high adaptability of pathogens and cost-effectiveness requirements, there is a need to change cultivation strategies by reducing the use of pesticides, promoting their precision and purposefulness. Smart or precision horticulture is a way to ensure this and provides a close linkage between research on local resources, environmental issues and information technologies, where common work can promote the development of fruit-growing. The aim of the study was the development of an integrated decision-making system using knowledge on plantpathogen-environment interactions in apple/V. inaequalis and pear/V. pyrina pathosystems. The following objectives were defined to fulfil the aim: 1) application of semantic analysis and data mining for plant-pathogen interaction data in apple/V. inaequalis and pear/V. pyrina pathosystems; 2) development and implementation of an image-based deep learning system for early identification and evaluation of apple and pear scab; 3) development of IoT–system model for apple and pear monitoring. The results of this study provided the knowledge on plant-pathogen interaction mechanisms, their use for disease monitoring and prognosis. [ABSTRACT FROM AUTHOR]

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-adaptated 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 understaning 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. [ABSTRACT FROM AUTHOR]

The aim of this article was to provide an overview on the current status of fruit tree diseases caused by Pseudomonas syringae, their importance and distribution, epidemiology and control possibilities with emphasis on plums and cherry. The plant diseases caused by Pseudomonas syringae are economically important and occur worldwide on large diversity of plants. On stone fruits, diseases caused by different pathovars of Pseudomonas syringae are economically important in major fruit growing regions. The severity of damages and economic importance depends on the geographical region, host plant species and pathovar of P. syringae involved in the disease. Bacterial canker induced by P. syringae pv. syringae on all commercially grown stone fruit species and by pv. morsprunorum predominantly on cherries and plums is considered to be the most serious one. Bacterial decline caused by P. syringae pv. persicae is severe on nectarine and peach. Despite the wide spread and economic importance in the most stone fruit growing areas the diseases caused by Pseudomonas syringae in some areas, e.g. Baltic States, are poorly studied, and the data on distribution and pathovars involved in the diseases observed are still missing. [ABSTRACT FROM AUTHOR]

In Latvia, the sown areas of oats (Avena sativa) have significantly increased during the last decade. Favourable climate conditions, varieties with high yield potential and effective disease control are necessary for obtaining high yields. The information regarding oat diseases in Latvia is incomplete. The identification of oat pathogens was carried out in this study. The main focus was on mycotoxins producing fungi in seed heads. Twenty oat fields with integrated and organic farming systems and one field from State Stende Cereals Breeding Institute were surveyed. In order to identify fungal species and assess their prevalence during the vegetation season of 2020, 10 seedlings with disease symptoms from ten places in the field were collected at the beginning of vegetation; similarly, 10 panicles with disease symptoms were collected shortly before harvesting. Plant parts were surface sterilised, and fungi were isolated on potato dextrose agar. Pure cultures of fungal isolates were grouped and presumptively identified based on colony and spore morphology. The pure culture collection was established for further studies. ITS1/5.8S/ITS2 region was sequenced for 44 isolates that included typical representatives of dominating fungal groups. Alternaria, Pyrenophora and Fusarium species dominated among the isolated fungi. In oat grains, toxins producing species such as F. poae, F. sporotrichioides, F. graminearum, and F. avenaceum were identified. More detailed research and analysis of obtained data are in progress. [ABSTRACT FROM AUTHOR]

Pyrenophora tritici-repentis is a major wheat pathogen in all wheat (Triticum spp.) growing areas worldwide. Up to date, eight P. tritici-repentis races have been described based on chlorosis, necrosis, or both symptoms caused on race differential wheat genotypes: ‘Glenlea’, 6B662, 6B365, and ‘Salamouni’. Symptom development on differential genotypes depends on the interaction of the pathogen’s necrotrophic effectors named Ptr ToxA, Ptr ToxB, and Ptr ToxC with host susceptibility genes. Ptr ToxA is encoded by the single copy gene ToxA and induces necrosis on sensitive wheat cultivars. Ptr ToxB causes chlorosis and is encoded by the multicopy gene ToxB. The Ptr ToxC is the non-proteinaceous, polar, low molecular mass molecule that also induces chlorosis, but up to date, the gene encoding this toxin is unknown. Races producing Ptr ToxA are predominant in the global Ptr population. There are several reports about new putative races of P. tritici-repentis that do not conform with the current race system, so further research is required. This study aims to collect and systematise available information about the virulence and races of P. tritici-repentis. [ABSTRACT FROM AUTHOR]