Viruses cause epidemics on all major crops of agronomic importance, and a timely and accurate identification is essential for control. High throughput sequencing (HTS) is a technology that allows the identification of all viruses without prior knowledge on the targeted pathogens. In this paper, we used HTS technique for the detection and identification of different viral species occurring in single and mixed infections in plants in Poland. We analysed various host plants representing different families. Within the 20 tested samples, we identified a total of 13 different virus species, including those whose presence has not been reported in Poland before: clover yellow mosaic virus (ClYMV) and melandrium yellow fleck virus (MYFV). Due to this new finding, the obtained sequences were compared with others retrieved from GenBank. In addition, cucurbit aphid-borne yellows virus (CABYV) was also detected, and due to the recent occurrence of this virus in Poland, a phylogenetic analysis of these new isolates was performed. The analysis revealed that CABYV population is highly diverse and the Polish isolates of CABYV belong to two different phylogenetic groups. Our results showed that HTS-based technology is a valuable diagnostic tool for the identification of different virus species originating from variable hosts, and can provide rapid information about the spectrum of plant viruses previously not detected in a region.

Senescence, despite its destructive character, is a process that is precisely-regulated. The control of senescence is required to achieve remobilization of resources, a principle aspect of senescence. Remobilization allows plants to recapture valuable resources that would otherwise be lost to the environment with the senescing organ. Autophagy is one of the critical processes that is switched on during senescence. This evolutionarily conserved process plays dual, antagonistic roles. On the one hand, it counteracts instantaneous cell death and allows the process of remobilization to be set in motion, while on the other hand, it participates in the degradation of cellular components. Autophagy has been demonstrated to occur in many plant species during the senescence of leaves and flower petals. Little is known, however, about the senescence process in other ephemeral organs, such as fine roots, whose lifespan is also relatively short. We hypothesized that, like the case of seasonal leaf senescence, autophagy also plays a role in the senescence of fine roots, and that both processes are synchronized in their timing. We evaluated which morphological and cytological symptoms are universal or unique in the senescence of fine roots and leaves. The results of our study confirmed that autophagy plays a key role in the senescence of fine roots, and is associated also with the process of cellular components degradation. In both organs, structures related to autophagy were observed, such as autophagic bodies and autophagosomes. The role of autophagy in the senescence of these plant organs was further confirmed by an analysis of ATG gene expression and protein detection. The present study is the first one to examine molecular mechanisms associated with the senescence of fine roots, and provide evidence that can be used to determine whether senescence of fine roots can be treated as another example of developmentally programmed cell death (dPCD). Our results indicate that there is a strong similarity between the senescence of fine roots and other ephemeral organs, suggesting that this process occurs by the same autophagy-related mechanisms in all plant ephemeral organs.

Tomato (Solanum lycopersicum) is one of the most important vegetables for fresh consumption and industry processing in the world. Recently, two thrips-transmitted tospoviruses, Tomato spotted wilt virus (TSWV) and Tomato yellow ring virus (TYRV) have been described as a potential threat to tomato crops worldwide (Margaria et al. 2015, Birithia et al. 2012). TSWV is known to occur on tomato in Poland, but TYRV is not. The genome of tospoviruses consists of three RNAs, large (L), medium (M) and small (S). The L RNA is organized in negative sense orientation, whereas the M and S RNAs are in ambisense (Adkins 2000). During 2013 to 2014, 18 samples of tomato plants with symptoms of necrosis on leaves and stalks, and chlorotic and necrotic ringspots on fruits from Kujawsko-Pomorskie region were tested at the Plant Disease Clinic of Institute of Plant Protection–National Research Institute in Poznań. The yield and quality losses in some of the greenhouses in Kujawsko-Pomorskie region were estimated at ca. 70% by...

Here we describe two Brome mosaic virus (BMV) isolates from the Wielkopolska region of Poland. The BMV-Sr and BMV-Sz isolates were collected from maize [Zea mays L. ssp. Indentata] and triticale [× Triticosecale Wittm. ex A. Camus] plants respectively. Newly emerged BMV isolates, similarly to the BMV-M2 strain derived from an Arkansas isolate, have a wide host range that includes species in the Poaceae and Fabaceae families. Furthermore, immunological reactions of icosahedral virions from non-inoculated cowpea [Vigna unguiculata L.] leaves with a specific immunoglobulin confirmed that each of these isolates can systemically infect cowpea. We characterized the BMV-Sr and BMV-Sz genomic sequences encoding the replication protein (1a), polymerase (2a), complete movement protein (3a) and coat protein (CP) genes. The 1a, 2a, 3a and CP gene sequences showed 98.9, 97.6, 98.4 and 97.7 % nucleotide sequence identity between the Polish isolates respectively. Phylogenetic analysis based on these four genes confirmed the species identity of the isolates. A phylogenetic tree based on RNA3 (3a and CP genes) showed independent clustering of the Polish isolates. Amino acid sequence analysis of the 3a protein revealed that both Polish isolates are characterized by a single amino acid mutation at the 81st position, when compared with the Russian isolate. It had been previously reported that four amino acid mutations in this region determined BMV systemic infection in cowpea. Our results indicate that a single non-synonymous substitution in the cell-to-cell movement protein may be crucial for the nature of cowpea infection.