Wheat dwarf virus (WDV) has been one of the most common viruses on cereal crops in Poland in the last years. This single stranded DNA virus is transmitted by the leafhopper spec, Psammotettix alienus (Dahlb.) in a persistent manner. It induces yellowing and streaking of leaves, dwarfing or even death of infected plants. The presence of barley- and wheat-specific forms of WDV (WDV-B and WDV-W) and their vector were previously reported in the country, however the literature data did not include any information on the infectivity of the vector in Poland. A duplex polymerase chain reaction (PCR) procedure was developed and optimized for simultaneous detection and differentiation of both forms in the vector. Two sets of primers amplify 734 bp and 483 bp specific fragments for WDV-W and WDV-B, respectively. The results were verified by a sequencing method. The studies were carried out on insect samples collected in autumn from four different locations in Greater Poland. The results confirmed the presence of WDV-W in the tested samples. They also suggested the concomitant of both forms of the virus in the vector. Additional studies to determine virus-vector relationships should be undertaken.

Water samples were collected from irrigation ditches and drainage canals surrounding fields in southern Greater Poland. Initially, the samples were subjected to low and highspeed centrifugation and obtained pellets were used to perform biological assays. Viral identification involved biological, electron microscopic as well as molecular methods. The occurrence of Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) was demonstrated in 12 of the 17 examined water sources. The molecular analysis results showed TMV and ToMV co-infections in the analysed water samples. To our knowledge, this is the first report of tobamoviruses being found in environmental water in Poland.

Plant viruses create many changes in the morphology of the plant cell once the infection process has begun. This paper describes and compares the ultrastructural changes induced in maize cells by two isolates of Maize dwarfmosaic virus (MDMV), Spanish (MDMV-Sp) and Polish (MDMV-P), and one isolate of Sugarcane mosaic virus (SCMV) at 10 and 42 days post-inoculation: the concentration and arrangement of virus particles, inclusion bodies associated with infection, and other cytological alterations. The most important difference between maize cells infected with MDMV isolates and with SCMV-P1 was in the form of cytoplasmic cylindrical inclusions. In cells infected with MDMV only typical inclusions such as pinwheels and scrolls were observed, but laminar aggregates were also present in SCMV-infected cells. No virus particles were found in plant cell organelles. Specific virion arrangements occurred in cells infected with MDMV-Sp and SCMV. The most interesting new finding was of specific amorphous inclusions in the cytoplasm of MDMV-Sp-infected cells, which clearly differentiated the two MDMV isolates studied.

In the spring of 2019, many plants, mainly winter wheat, were observed to have dwarfism and leaf yellowing symptoms. These plants from several regions of Poland were collected and sent to the Plant Disease Clinic of the Institute of Plant Protection – National Research Institute in Poznań to test for the presence of viral diseases. Double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) results showed numerous cases of Wheat dwarf virus (WDV) and a few cases of plant infections caused by Barley yellow dwarf viruses (BYDVs). WDV was detected in 163 out of 236 tested winter wheat plants (69.1%), in 10 out of 27 tested winter barley plants (37%) and in 6 out of 7 triticale plants (85.7%) while BYDVs were found, respectively, in 9.7% (23 out of 236) and in 18.5% (5 out of 27) of tested winter forms of wheat and barley plants. Infected plants came mainly from the regions of Lower Silesia and Greater Poland. Furthermore, individual cases of infections were also confirmed in the following districts: Lubusz, Opole, Silesia, Kuyavia-Pomerania and Warmia-Masuria. Results of Duplex-immunocapture-polymerase chain reaction (Duplex-IC-PCR) indicated the dominance of WDV-W form in wheat and WDV-B form in barley plants. Moreover, results of reverse transcription – polymerase chain reaction (RT-PCR) connected with restriction fragment length polymorphism (RFLP) analysis, performed for 17 BYDVs samples, revealed 8 BYDV-PAS, 4 BYDV-MAV and 2 BYDVPAV as well as the presence of two mixed infections of BYDV-MAV/-PAS and one case of BYDV-MAV/-PAV. Next, RT-PCR reactions confirmed single BYDV-GAV infection and the common presence of BYDV-SGV. To the best of our knowledge, in 2020 the viruses were not a big threat to cereal crops in Poland.

Maize dwarf mosaic virus (MDMV) is a serious and widespread virus pathogen of maize plants. This +ssRNA virus belongs to the Potyvirus genus in the Potyviridae family. Together with sugarcane mosaic virus (SCMV) it causes one of the most important viral diseases on maize crops in the world – maize dwarf mosaic. Both viruses are transmitted in the same non-persistent manner by several aphid species. They induce similar symptoms of leaf mosaic or mottling, stunting and a reduction in plant weight and grain yield. Available MDMV diagnostics include primarily commercialized enzyme-linked immunosorbent assays (ELISA) and reverse transcription-polymerase chain reactions (RT-PCR). Here, laborsaving reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay was optimized for identification of genetically different MDMV isolates. For this purpose, primer sets, MDMVF3/MDMVB3 and MDMVFIP/MDMVBIP amplifying fragments of coat protein coding sequence of MDMV, were used. The specificity of the reaction was verified using three MDMV (-P1, -Sp, -PV0802-DSMZ) and three SCMV (-P1, -PV0368- -DSMZ, -PV1207-DSMZ) isolates. Obtained products were visualised by DNA staining, electrophoretic separation as well as by real-time monitoring of the reaction. The sensitivity of RT-LAMP and conventional RT-PCR reactions was comparable. Both methods could detect virus as low as 550 fg · μl–1 of total RNA. This technique has application value for screening MDMV by phytosanitary services.