Erwinia amylovora-specifikus bakteriofágok növényen belüli szállítódása

Uptake and delivery of Erwinia amylovora-specific bacteriophages in plant tissues were studied in order to improve the efficacy of a phage-besed biocontrol method against the bacterial phytopathogen E. amylovora, which causes fire blight of pome fruits. An American (ΦEa104) and one of our own Hungarian phage isolates (H5K) were applied by two different methods on apple seedlings grown in perlite medium. Following phage application to the root zone, plant parts above ground level were assayed for phage titers. In case of spraying phages onto the surface of the stem and leaves the roots were examined for the presence of phages at various times. Both phage isolates were detectable in plant parts above ground level as well as in the roots, in most cases on the first sampling day after treatment. However, the titer of introduced phage suspensions measurably decreased, and after seven days of treatment we could not detect phages in any of the samples. Nevertheless, demonstration of the translocation ability of these phages could serve as a basis for further investigations that may promote the more efficient application of bacteriophages for the control of fire blight

A Piriformospora indica endofita gomba által indukált növényi rezisztencia mechanizmusa = Mechanism of disease resistance induced by endophytic fungus Piriformospora indica

A bazídiumos gombákhoz tartozó, a növények gyökerében élő endofita Piriformospora indica jelentősen fokozta az élő és élettelen stressz faktorok elleni ellenállóképességet különböző növényekben. Ennek a nagyobb tűrőképességnek a biokémiai hátterét vizsgáltuk árpában (Hordeum vulgare L.) és paradicsomban (Solanum lycopersicum L.), különös tekintettel az antioxidánsok hatására. A biotikus és abiotikus stressz élettani markerei, mint pl. az anyagcsere aktivitása, a membránok zsírsavösszetétele, lipid peroxidáció, aszkorbinsav és glutation koncentráció, valamint a kataláz, aszkorbát-peroxidáz, dehidroaszkorbát-reduktáz, monodehidroaszkorbát-reduktáz és glutation reduktáz enzimek aktivitása változásain keresztül értékelték a P. indica növényekre gyakorolt kedvező hatását. A P. indica megtelepedése a gyökéren fokozta a növények növekedését és enyhítette a NaCl és a fuzárium fertőzés káros hatását. Az endofita gomba jelentősen fokozta az aszkorbinsav mennyiségét és az antioxidáns enzimek aktivitását a stressz hatása alatt álló gazdanövényben. Feltételezhető, hogy a nagyobb antioxidáns aktivitással rendelkező növények fokozott mértékben képesek elviselni az oxidatív stressz hatását. | The root endophytic basidiomycete Piriformospora indica has been shown to increase tolerance to biotic and abiotic stress in various plants. Biochemical mechanisms underlying P. indica-mediated stress tolerance were studied in barley (Hordeum vulgare L.) and tomato (Solanum lycopersicum L.) with special focus on antioxidants. Physiological markers for biotic and abiotic stress, such as metabolic activity, fatty acid composition, lipid peroxidation, ascorbate and glutathione concentration and activities of catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase and glutathione reductase enzymes were assessed. Root colonization by P. indica increased plant growth and attenuated the detrimental effects of NaCl and pathogenic Fusarium spp on the colonized plants. The endophyte significantly elevated the amount of ascorbic acid and increased the activities of antioxidant enzymes in host plants under stress conditions. One can suppose that plants with improved antioxidant activities have a greater ability to cope with oxidative stress

Description of the Nicotiana benthamiana−Cercospora nicotianae Pathosystem

Nicotiana benthamiana is a valuable model organism in plant biology research. This report describes its extended applicability in the field of molecular plant pathology by introducing a nonbiotrophic fungal pathogen Cercospora nicotianae that can be conveniently used under laboratory conditions, consistently induces a necrotic leaf spot disease on Nicotiana benthamiana, and is specialized on solanaceous plants. Our inoculation studies showed that C. nicotianae more effectively colonizes N. benthamiana than its conventional host, N. tabacum. The functions of two critical regulators of host immunity, coronatine-insensitive 1 (COI1) and ethylene-insensitive 2 (EIN2), were studied in N. benthamiana using Tobacco rattle virus-based virus-induced gene silencing (VIGS). Perturbation of jasmonic acid or ethylene signaling by VIGS of either COI1 or EIN2, respectively, resulted in markedly increased Cercospora leaf spot symptoms on N. benthamiana plants. These results suggest that the N. benthamiana–C. nicotianae host–pathogen interaction is a prospective but hitherto unutilized pathosystem for studying gene functions in diseased plants. </jats:p

Near-Isogenic Barley Lines Show Enhanced Susceptibility to Powdery Mildew Infection Following High-Temperature Stress

Barley cultivation is adversely affected by high-temperature stress, which may modulate plant defense responses to pathogens such as barley powdery mildew (Blumeria graminis f. sp. hordei, Bgh). Earlier research focused mainly on the influence of short-term heat stress (heat shock) of barley on Bgh infection. In this study, our aim was to investigate the effects of both short- and long-term heat stress (35 °C from 30 s to 5 days) on Bgh infection in the barley cultivar Ingrid and its near-isogenic lines containing different powdery mildew resistance genes (Mla12, Mlg, and mlo5) by analyzing symptom severity and Bgh biomass with RT-qPCR. The expression of selected barley defense genes (BAX inhibitor-1, Pathogenesis- related protein-1b, Respiratory burst oxidase homologue F2, and Heat shock protein 90-1) was also monitored in plants previously exposed to heat stress followed by inoculation with Bgh. We demonstrated that pre-exposure to short- and long-term heat stress negatively affects the resistance of all resistant lines manifested by the appearance of powdery mildew symptoms and increased Bgh biomass. Furthermore, prolonged heat stress (48 and 120 h) enhanced both Bgh symptoms and biomass in susceptible wild-type Ingrid. Heat stress suppressed and delayed early defense gene activation in resistant lines, which is a possible reason why resistant barley became partially susceptible to Bgh