Fire blight is the most devastating disease affecting pome fruit production globally. The pathogen is native to North America and was imported to western Europe in the 1950s, progressively spreading over the continent in the ensuing decades. Previous phylogenetic studies have revealed the extreme genetic homogeneity of the pathogen outside its center of origin, which makes epidemiological studies difficult. These are generally only possible using hypervariable regions of the genome such as those represented by CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats), which are, however, not practical to sequence due to their size and variability. Here, we present a simple PCR assay targeting the duplication of a single CRISPR spacer in Erwinia amylovora that was found to be an important marker to discriminate between two main European populations of the pathogen. We implemented the assay on a total of 582 isolates to follow the spread of fire blight across the continent over several decades and, wherever possible, within single countries. The results obtained point to the occurrence of two major separate introduction events for E. amylovora in Europe that occurred approximately 20 years apart, and confirmed the existence of two principal distribution areas located in Northeastern Europe and the Eastern Mediterranean Basin from which the pathogen moved on to colonize the Eurasian continent.

Erwinia amylovora, the causal agent of fire blight, was first reported in Kyrgyz orchards in 2008 and, within a few years, the disease has spread throughout most of the northern part of the country. As fire blight expanded and penetrated new areas, it also reached the unique ecosystem constituted by the Arslonbob wild walnut-fruit forests in South Kyrgyzstan. Here, we present the results of field surveys in the forests and in the nearby orchards and gardens of the Jalal-Abad region during the 2019 season. Further, we use genetic profiling of the CRISPR regions to compare the genotypes of the obtained isolates to those of previous outbreaks in the north of the country and in nearby Kazakhstan. While fire blight was found in twelve of the twenty-six sites investigated in and around the Arslonbob walnut-fruit forest, it was mostly located on domesticated varieties of quince, apple or pear in gardens, orchards or nurseries. Plants in the forest and especially endangered wild species were not affected by the disease, but their proximity to the current infection herds is cause of major concern and calls for immediate protective action. Genetic analysis suggests that the main introduction route for fire blight to Central Asia was import of contaminated plant material from already affected countries in the Eurasian continent, which probably occurred on multiple independent instances. Nonetheless, indications of natural spread of the disease were identified between the regions of South Kazakhstan and North Kyrgyzstan.

Periods of unfavorable storing conditions can lead to changes in the quality of fish feeds, as well as the development of relevant mycotoxins. In the present study, a commercial fish feed was stored under defined conditions for four weeks. The main findings indicate that even storing fish feeds under unsuitable conditions for a short duration leads to a deterioration in quality. Mycotoxin and fungal contamination were subsequently analyzed. These investigations confirmed that different storage conditions can influence the presence of fungi and mycotoxins on fish feed. Notably, ochratoxin A (OTA) was found in samples after warm (25 °C) and humid (>60% relative humidity) treatment. This confirms the importance of this compound as a typical contaminant of fish feed and reveals how fast this mycotoxin can be formed in fish feed during storage.

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