Search Results

You are looking at 1 - 6 of 6 items for :

  • Author or Editor: B. Barna x
  • Biology and Life Sciences x
  • Refine by Access: All Content x
Clear All Modify Search

Heat shock treatment of near isogenic barley lines induced susceptibility against powdery mildew (Blumeria graminis f. sp. hordei, Bgh). When barley lines were immersed into hot water (48–49 °C) for 20 seconds one day before inoculation with Bgh race A6, the heat treatment increased susceptibility in susceptible barley cv. Ingrid and in its near-isogenic barley lines carrying different effective resistance genes. Microscopic investigations indicated vigorous development of the pathogen not only on heat treated susceptible Ingrid and resistant Mla, but also on Mlg-resistant and even mlo-resistant lines. However, when longer heat stress was used, infection density increased gradually on the susceptible Ingrid leaves, and the 40–50 sec heat treatment induced the development of visible powdery mildew colonies even on mlo leaves. Heat stress significantly increased leakage of ions from leaf segments from all barley lines with or without specific resistance genes and caused a late decrease of SOD and a slight increase in CAT enzyme activities, which correlated with the slightly down-regulated levels of hydrogen peroxide in the heat treated barley leaves. Significant increase of RNase activities was found after heat stress, and there was a slight degradation of total DNA as a consequence of heat pretreatment in all barley lines.

Restricted access

In the present work we aimed at comparing the effect of benzothiadiazole (BTH) treatment on defence reactions of sunflower plants to downy mildew and white rot diseases. BTH treatment resulted in reduced disease symptoms in biotrophic and in the early stage of the necrotrophic interactions. To get a better insight into the effect of BTH, changes in the activities of polyphenol oxidase and peroxidase enzymes, as well as the expression of the host response-associated sunflower genes were examined in the plants. Inoculation with Plasmopara halstedii enhanced the polyphenol oxidase and peroxidase enzyme activities, while inoculation with Sclerotinia sclerotiorum did it only at 4 dpi. However, most importantly, in each case extracts from BTH pretreated and inoculated plants showed the highest polyphenol oxidase and peroxidase enzyme activities. Similarly, the accumulation of GST and PDF transcripts was detected following inoculations with both biotrophic and necrotrophic pathogens, and again, BTH pre-treatment enhanced GST and defensine gene activities in the inoculated plants. We suggest that induction of enzyme activities, as well as of the elevated expression of GST, PDF and PR5 genes by BTH pre-treatment may be a significant part of the induced resistance of sunflower to downy mildew and white rot (white mold).

Restricted access

One of the most important diseases of pea is caused by Pea seed-borne mosaic virus (PSbMV), which has a relatively wide host range. Since there are few varieties with resistance against the virus, and spraying insecticides is not very effective, the determination of the disease and the pathogen in the seeds is very important. Inoculum prepared from pea seeds showing typical virus symptoms caused very mild symptoms on Chenopodium amaranticolor and C. quinoa, but several chlorotic/necrotic lesions on bean (Phaseolus vulgaris) cv. Scarlet, and systemic symptoms with mosaic and curling of top leaves on bean cv. Maxidor. The detection of the virus was carried out by PCR using universal primers and virus sequence analysis. According to the phylogenetic analysis the PSbMV isolate identified in Hungary belongs to the pathotype P1 and associated with the cluster 2 isolates.

Open access

The effects of Bipolaris sorokiniana inoculation on accumulation of hydrogen peroxide and changes in the activities of superoxide dismutase (SOD), catalase (CAT), non-specific peroxidase (PX) and β -1,3-glucanase enzymes in leaves of differentially resistant spring barley and meadow fescue were investigated in this study. Hydrogen peroxide accumulated slightly in inoculated barley leaves 24 hours after inoculation, and its accumulation after 48 hours of pathogenesis remained week around sites of infection. In leaves of fescue, which is more resistant to B. sorokiniana , accumulation of H 2 O 2 was faster and stronger in comparison to barley. A slight increase in SOD activity was observed only in infected fescue. Catalase activity in infected barely leaves decreased significantly 48 hours after inoculation, while in fescue-infected plants CAT activity, following a slight decrease, remained similar to the control values. PX activity was considerable lower in inoculated barley leaves after 6 hours, but at 24 and 48 hours after inoculation its activity increased significantly compared to the control. In inoculated fescue leaves activity of PX was higher at 6 and 24 hours compared to the control, while at 48 hours PX activity was strongly inhibited. β -1,3-Glucanase activity in inoculated barley plants did not differ from that of the control, while in infected fescue leaves it increased significantly 48 hours after inoculation. Based on the results, we suggest that the strong accumulation of H 2 O 2 , changes in antioxidant levels, together with the significant increase of β -1,3-Glucanase activity in infected fescue leaves, plays an important role in fescue’s greater resistance to B. sorokiniana .

Restricted access

Biotic and abiotic stresses induce increased formation of reactive oxygen species (ROS) through distinct pathways: pathogen infections activate specific ROS-producing enzymes (i.e. NADPH oxidase, cell wall peroxidases), which results in accumulation of cellular or intercellular ROS, such as superoxide or hydrogen peroxide. Abiotic stresses, on the other hand, cause elevated ROS production principally through an impairment of photosynthetic and respiratory electron transport pathways. Also, these two types of stresses have diverse effects on the antioxidant system of the plant. Results of experiments studying the interaction of abiotic and biotic stresses largely depend on the degree of the applied abiotic stress treatment, the compatible or incompatible host-pathogen interaction and the timing of inoculation in relation to the timing of a preceding abiotic stress treatment.

Restricted access
Acta Alimentaria
Authors:
Sz. Luzics
,
Á. Tóth
,
T. Barna
,
E. Szabó
,
I. Nagy
,
B. Horváth
,
I. Nagy
,
Z. Varecza
,
I. Bata-Vidács
, and
J. Kukolya

Abstract

Thermobifida alba is the mesophilic member of the Thermobifida genus, the genome and enzyme sets of which have not been described and published yet. Thermobifida strains are thermotolerant actinomycete, which possess wide sets of cellulose and hemicellulose hydrolysing enzymes. Previously, three endomannanases (Man5ATh, Man5ATc, and Man5AThf) of thermobifidas were cloned and investigated, and hereby the endomannanase of T. alba DSM 43795 is described. All four endomannanases belong to the glycoside hydrolase family 5, their sizes are around 50–55 kDa. Their structure consists of a catalytic domain and a carbohydrate binding module, while there is an interdomain linker region in-between consisting repetitive tetrapeptide motifs (eg.: PPTEPTD-Ta, PTDP-Tc, TEEP-Tf, DPGT-Th). The pH optima of Man5A enzymes from T. alba, Thermobifida halotolerans, Thermobifida cellulosilytica, and Thermobifida fusca are slightly different (6.5, 7.0, 7.5, and 8.0, respectively), however, the temperature optima of the enzymes were detected within a wider range of 65–75 °C. In this research, Man5ATa exhibited the lowest Michaelis-Menten constant (KM) (0.13 mM) on LBG-mannan substrate, while others shared similar kinetic parameters: 0.9–1.7 mM of KM. Despite the high sequence similarity of the investigated mannanases, they exhibit different temperature stability parameters. These different functional characteristics can be advantageous for industrial applications producing biologically active, oligomannan prebiotics under different conditions.

Open access