We found that resistance to pepper powdery mildew (PM) (Leveillula taurica) develops in a sweet pepper (Capsicum annuum) cultivar ('Totál') when grafted on a resistant cherry pepper (C. annuum var. cerasiforme) rootstock (cv. Szentesi). Resistance is manifested both towards PM symptoms and pathogen accumulation. In healthy, uninfected plants PM-resistance can be predicted by enhanced accumulation of the reactive oxygen species (ROS) superoxide (O 2 .2) and activity of NADPH oxidase, the enzyme mainly responsible for pathogenesis-related superoxide generation. In L. taurica-inoculated PM-resistant 'Szentesi' high levels of superoxide and NADPH oxidase activity are sustained even 45 days after inoculation, as opposed to PM-susceptible 'Totál'. This is also true for 'Totál' grafted on resistant 'Szentesi' rootstocks, where PM resistance, enhanced superoxide production and NADPH oxidase activity is likely due to an unknown, graft-transmitted signal. To further elucidate the mechanisms of graft-transmissible PM-resistance we monitored expression of pathogenesis-related (PR) genes in healthy and infected plants. In healthy plants, expression of CaPR-1 is several times higher in leaves of PM-resistant pepper than in sensitive plants, while high expression of CaPR-2 (glucanase) does not entirely correlate with PM-resistance, being detectable only in PM-resistant 'Szentesi'. However, during advanced stages of PM-pathogenesis (45 DAI) expression of CaPR-1 and CaPR-2 is by far the highest in PM-susceptible 'Totál'. Our results suggest that the direct biochemical cause of graft-transmissible PM-resistance in pepper is the enhanced accumulation of NADPH oxidasegenerated superoxide. To our knowledge, this is the first report on the role of ROS (superoxide) in graft-transmissible, pathogen-specific disease resistance. Keywords Capsicum annuum var. cerasiforme Á Grafttransmissible resistance Á Leveillula taurica Á Superoxide Á NADPH oxidase Á Pathogenesis-related genes Communicated by E Kuzniak-Gebarowska.
In the publications available for us, exact levels of physical factors and those of the growing technology determining Ca2+ deficiency are rarely detailed. Although the influencing role of the various environmental factors (humidity, light, temperature) is known, we had only little information about their exact values which could be presented for the growing practice. Sweet pepper varieties of the same type grown in various substrates responded to the environmental factors in different ways. Our results revealed that increasing temperature of the root zone had the most significant effect on the incidence of Ca2+ -deficient fruits. Their amount, however, gave different results depending on the growing substrate. In forced sweet pepper grown in soil the proportion of Ca2+ - deficient fruits were significantly lower compared to the plants grown on rockwool. Fruits derived from forcing on perlite, in container were damaged the least by the blossom end rot deficiency symptoms. Our experimental results and technological suggestions are based on measurement results of three years.
Antioxidants are compounds that inhibit combustion (oxidation) processes. Antioxidants are vital components of our body, which can be obtained in part through plant nutrition. Therefore, it is very important to study species that have significantly higher antioxidant capacity than other species. The aim of the study was to investigate the antioxidant capacity of total polyphenols (TPC) of European mistletoe (Viscum album L.) leafy shoots collected from different species of trees (black locust, European ash, white poplar, field maple and black walnut) based on different methods; DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (ferric reducing antioxidant power) and TPC (total phenolic contents). The results proved that the antioxidant effect of leafy shoots from European ash (Fraxinus excelsior) against hydroxyl radicals (ROS) showed significantly higher values than those of the other four tree species. We found that the DPPH, FRAP and TPC methods show significant differences in antioxidant effect of European white mistletoe leafy shoots on the studied tree species and tea brands. However, the FRAP method shows higher sensitivity for trees but for tea brands, the DPPH method is more sensitive. The reason for the difference might be explained by the different methods of drying. In the future, we consider it feasible to plant ash groves at an altitude of at least 80 m above sea level in a closed area, where we can start growing European white mistletoe as an herb. Based on the results obtained European white mistletoe can be recommended as an herb to natural medicine for supplementary treatment of several cancer diseases.
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