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  • Author or Editor: I. Cernák x
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Seven complex compounds exhibiting the compositions Ni(en)3Ni(CN)4·H2O (I), Ni(en)3Ni(CN)4 (II),α-Ni(en)2Ni(CN)4 (III), Ni(en)Ni(CN)4·2H2O (IV), Ni(en)Ni(CN)4 (V), Ni(en)2Ni(CN)4 · 2.5H2O (VI) andβ-Ni(en)2Ni(CN)4 (VII) were prepared from the system Ni-en-[Ni(CN)4]2−-H2O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)→(II)→(III)→(V)⇄(IV) and (VI)→(VII)→(III)→(V)⇄(IV) Process (VII)→(III) represents isomerization. The reversibility of the process (V)⇄(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Abstract  

Two new tetracyano complexes of the composition MnenNi(CN)4 and MnenCd(CN)4 were prepared and identified. Their struture and properties were investigated by IR and UV-VIS spectroscopy, X-ray powder diffraction and by measuring magnetic moments. The results were confronted with the structure and properties of the compounds CdenNi(CN)4 and CdenCd(CN)4. The results of this study show a considerable similarity between these groups of compounds. The thermal behaviour of all the examined compounds was investigated derivatographically. The following order of thermal stability of the investigated complexes was observed: Cd−Cd(215°C)<Mn−Cd(250°C)<Cd−Ni(275°C)<Mn−Ni(310°C)

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In this study molecular markers linked to the Ry sto gene, which originates from the wild potato species Solanum stoloniferum and confers extreme resistance against PVY, were identified and the applicability of recently published Ry sto markers was analyzed. Three RAPD markers covering a total distance of 8.60 cM were detected in this experiment. The closest of these markers was located 0.53 cM from the gene. From among the published markers only one had diagnostic value in the experimental plant material, and mapped 2.95 cM from the gene, on the side opposite the RAPD markers developed in the present study. All the markers analyzed were present in Solanum stoloniferum accessions, irrespective of their resistance, indicating that these sequences are linked to the locus and not exclusively to the dominant allele of the Ry sto gene in the wild species. The inapplicability of several published markers indicates that the genetic background is decisive in this tetraploid and highly heterozygous species. This means that it may be necessary to develop markers from the breeding material itself, until the resistance gene is not cloned and cannot be used as a selection marker in marker-assisted selection.

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Late blight disease caused by Phytophthora infestans is one of the most destructive diseases of potato. In the host an arsenal of genes may contribute to the resistance against the pathogen. In the presently available cultivars besides the so called field resistance which is conditioned by an unknown number of minor genes, race specific resistance genes were introgressed. Recently, broad spectrum resistance genes were identified, isolated and incorporated in breeding programs. The inbreeding depression that is characteristic for potato and the different sexual crossability problems associated with the potential resistance gene sources further complicate the development of cultivars with durable late blight resistance. The task to produce genotypes with resistance is challenged also by the recent occurrence of rapidly changing genotypes of the pathogen which are able to reproduce also sexually nowadays worldwide. Due to its importance, the genetic background of late blight resistance is intensively studied. The growing number of isolated major resistance genes and other genes involved in resistance response, as well as the identified QTLs allow the development of molecular tools which may be effectively used in breeding. In this review the complex status of resistance in potato to P. infestans and the breeding aspects of it is discussed.

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