Apple scab caused by the pathogenic fungus Venturia inaequalis causes significant damage to apples. The creation of apple-scab resistant varieties is considered an alternative to pesticide-based management. To evaluate R gene inheritance, 862 apple hybrid samples were analyzed and divided into populations depending on the resistance genes (Rvi6 and Rvi5) present in the parents’ genotypes and their combinations. The field evaluation was carried out in 2016–2018 using the international VINQUEST scab evaluation methodology, but the genes were identified using specific scab resistance-gene molecular markers. Parent plants were genotyped using 22 SSR markers. The study determined that the field resistance of apple scab is influenced not only by the resistance genes present in the genotype but also by the genetic background of the apple cultivar, the tree’s general health status and resistance to other diseases. It was found that the apple scab resistance genes Rvi6 (Vf) and Rvi5 (Vm) are inherited according to Mendelian laws, and when both genes are pyramided in offspring, they are inherited as separate genes. In general, the inheritance of both genes in the offspring is not a determining factor for apple field resistance, as field resistance to scab is influenced by a combination of several factors.

Genetic Resources, oregano (Origanum vulgare L.) is included in the List of 'Priority Species' of medicinal and aromatic plants (Barata et al., 2010). Wide use of oregano biomass in phytomedicine, production of essential oil, perfumery, culinary, food and beverage production, beekeeping, etc. is one of the reasons why the wild populations should be conserved. In addition, cultivation of oregano is providing material for further processing. Cultivation of oregano accessions resistant to biotic pathogens is required to ensure high yields and high product quality in agricultural systems.Oregano is susceptible to infectious diseases caused by pathogenic fungi. Several oregano fungal diseases have been reported.In the United States, fungi of the genera Alternaria, Botrytis, Helminthosporium and Stemphylium on leaves, as well as fungi from the genus Pythium, which cause symptoms of root rot have been reported (Farr et al., 1995). In Poland, fungi such as Fusarium spp., Boeremia exigua var. exigua and Rhizoctonia solani had been obtained from roots and stems, but Alternaria alternata, Colletotrichum fuscum and Stemphylium botryosum had been isolated from leaves (Wielgusz and Seidler-Łożykowska, 2017;Zimowska, 2015). Research of fungal diversity on oregano leaves in Latvia identified similar fungi as in the mentioned studies.Members of the Truncatella genus have a wide geographic distribution. They are commonly associated with plants, either as endophytes or as pathogens in a wide array of plant species. Truncatella angustata was first described by Persoon in 1801 under the name Stilbospora angustata, which was subsequently revised to T. angustata (Hughes, 1958). T. angustata has been recognized as an endophyte and a saprotroph but also as a pathogen on various vascular plants in both tropical and temperate regions. It has been reported

European pear rust is an important disease; however, the relationship between its causal pathogen Gymnosporangium sabinae (Dicks.) Oerst. and host Pyrus communis L. is poorly understood. In this study, disease severity was measured, and leaf samples were collected over three years, and their leaf water content; leaf area; leaf mass per area; and epidermis, mesophyll, and vascular tissue width and stomatal density were measured and compared between susceptible and resistant genotypes for each year. Most genotypes either showed consistent disease symptoms or showed no symptoms during the study in terms of their susceptibility. A correlation between disease severity and mesophyll tissue thickness, and stomatal density and differences between several morphological parameters were found depending on the genotype’s susceptibility. The study showed that the following pear morphological traits were stable between the years: water content, leaf mass per area, spongy mesophyll thickness, phloem thickness, and stomatal density. When selecting for breeding, we found that candidates for traits that discern susceptible genotypes from resistant were mesophyll layer width, stomatal density, epidermis width, and xylem tissue width.

No abstract

The aim of the trial was to determine the optimal propagation methods for three Japanese quince cultivars. Rooting trials with cultivars ‘Darius’, ‘Rasa’, and ‘Rondo’ were conducted in 2017–2019 in a greenhouse, to investigate the rooting and shoot quality of softwood cuttings, using different treatments. At the beginning of fruit production, growth and amount of the first yield was evaluated depending on propagation method. Softwood cuttings of Japanese quince rooted well (average 82–93%) in a greenhouse with heated substrate and partly automated temperature and moisture control, in spite of different weather conditions during three vegetation periods. The best results for rooting were found for cultivar ‘Rondo’. On average, better results of rooting for all cultivars were obtained when cuttings were soaked in indolylbutiric acid solution and trichodermin was added to the substrate. Significant differences in length and diameter of the bush shoots found between years for both propagation methods and also between years for one type of propagation. On average, microproagated plants had the highest shoot length. After evaluating the first yield, no significant differences were found between cultivars during the first two trial years, but micro-propagated plants had significantly higher yield per bush.