Phytoplasma and phytoplasma diseases: a review of recent research

Numerous yellows-type diseases of plants have been associated with wall-less prokaryote pathogens \u2013 phytoplasma over the last 40 years. These pathogens cannot be grown in axenic culture so that advances in their study are mainly achieved by molecular techniques. Severe disease epidemics associated with a phytoplasma presence have been described worldwide. These include coconut lethal yellowing in Africa and the Caribbean, grapevine yellows in major viticultural areas and various diseases affecting stone and pome fruit plants. Phytoplasma-infected plants exhibit symptoms suggesting a profound disturbance in the normal balance of growth regulators and also yellows symptoms, but very often the symptomatology is not diagnostic. Detection and characterization of phytoplasmas infecting different plant species are now possible with molecular methods, based on the study of 16S rDNA polymorphisms. Molecular diversity of phytoplasmas is also demonstrated by studying genes coding the ribosomal proteins S3, tuf, SecY, amp, imp and other genes. Four phytoplasma genomes have been fully sequenced, including those of two \u2018Candidatus Phytoplasma asteris\u2019 strains, and those of strains of \u2018Ca. P. mali\u2019 and \u2018Ca. P. australiense\u2019. Three of these genomes contain large amounts of repeated DNA sequence, and the fourth carries multiple copies of almost 100 genes. Considering that phytoplasmas have unusually small genomes, these repeats might be related to their transkingdom habitat and to their pathogenic activity. An outlook of recent findings in the field is also repor

The special characteristics of the Hungarian national economic competitiveness

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Log-domain Universal Biquad Filter Design Using Lossy Integrators

In this paper, a new current mode low voltage log domain Class A universal biquad filter is proposed. The proposed circuit is derived from the block diagram based on Kerwin-Huelsman-Newcomb (KHN) circuit using lossy integrators. The circuit can provide second-order low pass,band pass and high pass filter characteristics. State space method and translinear principle is used for circuit synthesis.The natural frequency f0 and quality factor Q of the circuit is electronically tunable by varying amplitudes of the current sources. PSpice simulation results are given in order to verify the theoretical analysis. The simulations are performed with both ideal transistor models and AT&T CBIC-R type real transistor models

Selection of Non-Mycotoxigenic Inulinase Producers in the Group of Black Aspergilli for Use in Food Processing

Research background. Inulinases are used for fructooligosaccharide production and they are of interest for both scientific community and industry. Black aspergilli represent a diverse group of species that has use for enzyme production, in particular some species are known as potent inulinase producers. Finding new potential producers from the environment is as important as improving the production with known strains. Safe use of enzymes produced by aspergilli in food industry is placed ahead of their benefit for inulinase production. Experimental approach. Here we show a specific approach to finding/screening of newly isolated fungal inulinase producers that combines a newly developed screening method and an equally important assessment of the toxigenic potential of the fungus. In this study 39 black aspergilli collected from different substrates in Serbia were identified and assessed for inulinase production. Results and conclusions. The most common species were Aspergillus tubingensis (51.2 %), followed by A. niger (23.1 %), A. welwitschiae (23.1 %) and A. uvarum (2.6 %). The isolates for inulinase production were selected using a cheap and easy, fast and non-hazardous alternative inulinase screening test developed in this work. Enzymatic activity of selected inulinase-producing strains was confirmed spectrophotometrically. Since some A. niger and A. welwitschiae strains are able to produce mycotoxins ochratoxin A (OTA) and fumonisins (FB), the toxigenic potential of selected inulinase producers was assessed analytically and genetically. Fungal enzyme producer can be considered safe for use in food industry only after comparing the results of both approaches for investigating toxic potential, the direct presence of mycotoxins in the enzyme preparation (analytically) and the presence of mycotoxin gene clusters (genetically). In some strains the absence of OTA and FB production capability was molecularly confirmed by the absence of complete or critical parts of biosynthetic gene clusters, respectively. The two best inulinase producers and mycotoxin non-producers (without mycotoxin production capability as additional safety) were selected as potential candidates for further development of enzyme production. Novelty and scientific contribution. The presented innovative approach for the selection of potential fungal enzyme producer shows that only non-toxigenic fungi could be considered as useful in food industry. Although this study was done on local isolates, the approach is applicable globally

Design of log domain differential class AB universal biquad filter by employing lossy integrators

A new current mode low voltage differential Class AB second order universal biquad filter has been designed in this work. In design process, inspiring from Kerwin-Huelsman-Newcomb circuit, the circuit is realized with lossy integrators. The circuit has fundamental filter outputs namely; low pass, high pass and band pass. All pass and notch filter outputs have also been obtained by using additional circuits. In circuit design process, the state space method and translinear principle have been used. Two of the circuit parameters are electronically tunable which are the quality factor Q and the pole frequency f0. PSpice circuit simulations have been obtained to check the theoretical results’ validity. In PSpice simulations, both ideal and AT&T CBIC-R type real transistor models have been used

Utvrđivanje prisustva Colletotrichum acutatum u latentno zaraženom lišću i lisnim drškama jagode

Colletotrichum acutatum is the most significant agent of anthracnose strawberry fruit rot. Besides being a necrotrophic pest, it can spend a part of its life cycle as an epiphyte, in a form of latent infection. The presence of the fungi on symptomless plant tissue is considered one of the main ways of distribution of this economically harmful pathogen in the world. Investigation of latent C. acutatum infection was carried out on artificially inoculated strawberries. The initiation of fungi sporulation on symptomless petioles and leaves was carried out by exposing them to the herbicide paraquat (0.25%) and low temperatures, which caused plant tissue decay in different ways. Surface sterilization with 0.5% NaOCl precedes the exposure of plant material to paraquat. The freezing procedure was carried out by exposure of plant material to the temperature of -20°C for 2h. After the freezing, one group was rinsed in Tween 20 (18 μl/l), and another group underwent surface sterilization in 0.0525% NaOCl with an addition of Tween 20 (18 μl/l). After 6 days of incubation, the appearance of acervuli and conidia was detected in 93.33 to 100% plant parts exposed to paraquat treatment and freezing procedure. In inoculated parts which were not exposed to herbicides or low temperatures, the presence of acervuli was detected in 3.33% tested petioles and 6.67% leaves.Colletotrichum acutatum je najznačajniji prouzrokovač antraknoznog propadanja plodova jagode. Pored nekrotrofnog načina parazitiranja, deo svog životnog ciklusa može da provede kao epifit i to u vidu latentnih zaraza. Prisustvo gljive na asimptomatičnom biljnom tkivu smatra se jednim od glavnih načina širenja ovog ekonomski štetnog patogena u svetu. Ispitivanja latentne zaraze C. acutatum urađena su na veštački inokulisanim jagodama. Iniciranje sporulacije gljive na asimptomatičnim lisnim drškama i lišću urađeno je izlaganjem biljnog tkiva delovanju herbicida parakvata, kao i niskim temperaturama, koji na različite načine izazivaju propadanje biljnog tkiva. Izlaganju asimptomatičnih biljnih delova delovanju parakvata (0,25%), prethodila je površinska sterilizacija 0,5% NaOCl. Postupak smrzavanja urađen je izlaganjem biljnih delova temperaturi od -20oC u trajanju od 2 h. Posle smrzavanja jedna grupa je isprana Tween 20 (18 μl/l), a druga grupa je površinski sterilisana 0,0525% NaOCl uz dodatak Tween 20 (18 μl/l). Posle šest dana inkubacije, pojava acervula i konidija detektovana je u 93,33% do 100% lisnih delova izloženih delovanju parakvata ili postupcima smrzavanja. U inokulisanim biljnim delovima koji nisu izlagani delovanju herbicida ili niskih temperatura, sporulacija je detektovana kod 3,33% testiranih lisnih drški, odnosno 6,67% lišća

Morfološke, serološke i molekularne analize prouzrokovača antraknoze ploda banane

Two species of the genus Colletotrichum, C. musae and C. gloeosporoides, occur as infecting species of banana. The study focused on examining the etiology of anthracnose on banana fruits sold on the domestic market. An isolate was obtained from a deseased banana fruit on PDA medium, forming a white colony with intensive and uniformed growth. It was not possible to identify the isolated fungus based on its morphological characteristics. Positive serological reaction in an ELISA test with monoclonal antibodies for C. acutatum indicated an antigen site for the used monoclonal antibodies. Positive reaction when C. gloeosporioides-specific primers were applied indicated a similarity in the ITS sequence of the fungus and the examined isolate from banana fruit. Although there are no available data in literature that C. gloeosporioides-specific CgInt primer can be used for amplification of the phylogenetically related C. musae, our results do not exclude that the isolate could be C. musae. The host plant, symptoms observed and colony characteristics of the fungus isolated from the banana fruit mostly correspond to C. musae. Based on morphological, antigen and gentic characteristics, the isolate from banana was determined as Colletotrichum sp., while species identification of the anthracnose-causing agent on banana requires additional analysis.Na banani se javljaju dve vrste iz roda Colletotrichum, C. musae i C. gloeosporoides. Cilj ovog rada bio je ispitivanje etiologije antraknoznog propadanja plodova banane koje se u našoj zemlji nalaze u prometu. Iz obolelog ploda banane dobijen je izolat koji na PDA podlozi formira koloniju bele boje sa intenzivnim uniformnim rastom. Na osnovu dobijenih morfoloških osobina izolovane gljive nije se mogla definitivno uraditi identifikacija. Pozitivna serološka reakcija u ELISA testu sa monoklonalnim antitelima za C. acutatum govori o postojanju antigenog mesta za korišćena monoklonalna antitela. Pozitivna reakcija korišćenjem prajmera specifičnih za C. gloeosporioides ukazuje na sličnost u sekvenci ITS regiona ove gljive i ispitivanog izolata iz banane. Mada u literaturi nije zabeleženo da se korišćenjem CgInt prajmera specifičnog za C. gloeosporioides može amplifikovati i njemu filogenetski bliska C. musae, ovi rezultati ne isključuju mogućnost da je izolat iz banane C. musae. Biljka domaćin, zabeleženi simptomi i osobine kolonije izolata iz banane najviše odgovaraju C. musae. Na osnovu dobijenih rezultata morfoloških, antigenih i genetskih osobina izolat iz banane označen je kao Colletotrichum sp., a za tačnu identifikaciju prouzrokovača antraknoze ploda banane do nivoa vrste neophodno je sprovesti dalje analize