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  • Author or Editor: A. Bittsánszky x
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Okra seedlings tolerated soil-borne Rhizoctonia infection in strain dependent manner. No connection was revealed between pathogenicity of strains and their origin or taxonomic position. However, the okra proved to be susceptible to strains highly pathogenic to other host plants as well. R. zeae, a species new to European flora, was as aggressive to okra as the most potent R. solani strains. The effect of Rhizoctonia infection was more prominent on mass accumulation in hypocotyls than in cotyledons. The protein content and glutathione S-transferase activity increased in parallel with the evolution of disease syndrome. Metalaxyl, an acetanilide type systemic antioomycete fungicide induced glutathione S-transferase activity in cotyledons with 24 hours a phase, and this induction was more outstanding in symptomless seedlings grown in Rhizoctonia infested soil. It might be concluded, that the stress response of plants in tolerant host/parasite pair takes effect at higher level than in susceptible relationships.

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Total mineral uptake capacity of zucchini (Cucurbita pepo L. cv. giromontiina) grown in an experimental field at Gödöllő was studied. The mineral content of the soil (brown acidic sandy forest soil) showed unexpectedly high content (mg kg−1 DW) of Ba (95.5), Cr (32.9), Ni (27.8), Pb (15.4) and Zn (53.3). Boron (B) concentration of the soil was relatively low (7.1 mg kg−1 DW), but its bioaccumulation content in root, (2.5) shoot, (33.1) and leaf (50.1) tissues of the plant (mg kg−1 DW). Zinc (Zn) was also bioaccumulated in the plant with contents (mg kg−1 DW) of 47.1 (roots), 23.0 (shoots) and 56.1 (leaves) as compared with 53.3 (in the soil). Toxic element exclusion was observed in zucchini (mg kg−1 DW) concerning Ba (29.0), Co (0.2), Cr (5.3), Ni (5.8) and Pb (3.4) measured in the roots when compared with their concentrations in the soil: Ba (95.5), Co (10.2), Cr (32.9), Ni (27.8) and Pb (15.4). In silico sequence analyses of nucleotide and amino acid sequences of aquaporins (NIP, TIP, SIP and Si-TRP), boron-exporters (BOR), and rbcL of cpDNA revealed plant species with high sequence similarities to the sequences of Cucurbits, which predicted additional plants with intensive mineral (B and Zn) uptake capacity, similar to Cucurbits with phytoextraction potential.

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As DNA methylation patterns are inherited (‘epigenetic memory’) gsh I transgenic poplar ( Populus × canescens ) clones (11 ggs and 6 Lgl ) were treated with the DNA demethylating drug DHAC (5,6-dihydro-5′-azacytidine hydrochloride) at 10 −4 M for 7 days in order to study acquired plant molecular defense mechanisms in novel plant sources. In this study, the response of relative gene expression levels of transgene gsh I and poplar gene gsh 1 to DHAC treatment were analyzed by qRT-PCR ( q uantitative r everse t ranscriptase PCR). High expression levels of transgene gsh I were observed in the 6 Lgl clone (13.5-fold increase) compared to 11 ggs (1.0) sample. The expression level doubled (1.8-fold increase) in the DHAC-treated 6 Lgl samples but not in the 11 ggs clone (0.4-fold). Contrary to this, the relative copy number of transgene gsh I in the 6 Lgl clone was found to be 60% less (1.0) than in the 11 ggs sample (1.6). Relative expression level of endogenous poplar gene gsh 1 showed significantly higher responsiveness to DHAC-induced demethylation than the transgene gsh I with the highest expression level in the untransformed WT poplar (19.7-fold increase) compared to transformed clones of 6 Lgl (8.7-fold increase) and 11 ggs (2.5-fold increase), respectively. Competition in the reactivation capacity between transgene gsh I and poplar gsh 1 of 6 Lgl clone was also observed as the relative gene expression level of transgene gsh I increased from a high relative expression level (13.5) up by about twofold (1.8 times) rate (to 23.7) compared to poplar gsh 1 gene that increased by an 8.7 increment from a lower level (1.6 rel. expression) to 13.9.

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