For the years 2012–2018, we investigated the occurrence of storage diseases caused by fungi on four cultivars of apples grown in the central part of Poland. The fruits were picked in orchards managed with Integrated Pest Management (IPM) practices and stored in a cold room for 5–7 months. Depending on the season, apple cultivar and localization of orchard, the incidence of diseases was different. On apple cvs “Gala”, “Ligol” and “Golden Delicious”, bull’s eye rot (Neofabraea spp.) was the most frequently observed disease, whereas on apple cv. “Gloster”, gray mold (Botrytis cinerea) predominated. The blue mold (Penicillium expansum), brown rot (Monilinia spp.) and fungi of Alternaria spp. occurred at significantly lower intensity. We detected the occurrence of the new storage diseases of apples caused by Colletotrichum spp., Neonectria ditissima and Diaporthe eres.

Tracking newly emergent virulent populations in agroecosystems provides an opportunity to increase our understanding of the co-evolution dynamics of pathogens and their hosts. On the one hand host plants exert selective pressure on pathogen populations, thus dividing them into subpopulations of different virulence, while on the other hand they create an opportunity for secondary contact between the two divergent populations on one tree. The main objectives of the study were to explore whether the previously reported structure between two Venturia inaequalis population types, virulent or avirulent towards Malus x domestica cultivars carrying Rvi6 gene, is maintained or broken several years after the first emergence of new virulent strains in Poland, and to investigate the relationship between ‘new’ and ‘native’ populations derived from the same commercial orchards. For this purpose, we investigated the genetic structure of populations of the apple scab fungus, occurring on apple tree cultivars containing Rvi6, Rvi1 or Rvi17 resistance gene or no resistance at all, based on microsatellite data obtained from 606 strains sampled in 10 orchards composed of various host cultivars. Application of genetic distance inferring and clustering methods allowed us to observe clear genetic distinctness of the populations virulent towards cultivars carrying Rvi6 gene from the Rvi6-avirulent populations and substructures within the Rvi6-group as a consequence of independent immigration events followed by rare, long-distance dispersals. We did not observe such a structuring effect of other genes determining apple scab resistance on any other populations, which in turn were genetically homogenous. However, in two orchards the co-occurrence of strains of different virulence pattern on the same trees was detected, blurring the genetic boundaries between populations. Among several resistance genes studied, only Rvi6 exerted selective pressure on pathogens populations: those virulent toward Rvi6 hosts show unique and clear genetic and virulence pattern. For the first time in commercial Malus x domestica orchards, we reported secondary contacts between populations virulent and avirulent toward Rvi6 hosts. These two populations, first diverged in allopatry, second came into contact and subsequently began interbreeding, in such way that they show unambiguous footprints of gene flow today.

During the summers of 2013–2014, symptoms similar to viscid rot and upright disease were observed on cranberries (Vaccinium macrocarpon) on one plantation in central Poland. The associated fungi were isolated from symptomatic plant tissue. On the basis of morphological and cultural characteristics and the ability of isolated fungi to elicit viscid rot symptoms on cranberry fruits, they were classified as the genus Diaporthe. Further analysis of ITS sequence data allowed for the classification of the newly obtained isolates as D. vaccinii. Additional analysis of genetic diversity using five RAPD and eight ISSR primers constituted additional confirmation of genetic distance existing between closely related D. vaccinii and D. eres species, enabling their differentiation.

Triggering the plant resistance induction phenomenon by chemical compounds, for example acibenzolar-S-methyl ester, has been known and described in scientific literature. Other benzothadiazole derivatives have been also described; however, their properties have not been sufficiently studied. The tested substance, N-methyl-N-methoxyamide-7-carboxybenzo(1.2.3)thiadiazole (BTHWA), is an amide derivative of benzothiadiazole, showing a stimulating effect on plant growth, apart from its plant resistance inducing activity. This article presents the impact of BTHWA, used solo and in the program with fungicides, on the strawberry plants development, fruits health, yield, and quality parameters of the crop. The results show that the combined use of BTHWA and fungicides had a positive impact on the plants health and fruit health and nutraceutical and nutritional composition of compounds when compared to the results obtained when strawberries were treated only with the BTHWA or the fungicide. As a result of BTHWA use, the partitioning of assimilates has changed, which directly translated into the results of the conducted experiments. A reduction in the respiration of the fruit during storage was also observed, possibly due to a reduced disease infestation and a lower dry matter content in the fruit. A correlation between the parameters determined during the experiment was found. The BTHWA mode of action was evidenced to be beneficial to strawberry plants and fruit.