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  • Author or Editor: J. Taller x
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The biosynthetic pathways of essential and secondary products are well known in most plants. The rapid development of molecular genetic techniques in recent decades has facilitated the isolation and functional characterisation of genes from various organisms. Although pepper is not an optimal model for genomic analyses, many important genes have been isolated and characterised from this plant. In the present paper, pepper genes with known functions, such as taste or colour formation or the development of resistance responses, are reviewed, together with other information on pepper genomics. Flowcharts demonstrating the biosynthetic pathways described in the paper can be found in various places, e.g. on the Internet.

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The herbarium of Paulus Kitaibel (1757–1817) has been preserved in good condition and can still be used for the investigation of problematic questions. There happens to be a misidentified specimen on the back of one of the sheets. Although it has been studied by several botanists, it has proved impossible to identify this species because important morphological traits have been lost due to the age of the preserved material. The complete ITS region of the over 200-year-old herbarium specimen has been amplified by PCR. Sequence analysis and the secondary structure modelling of the ITS2 RNA transcript clearly provided, that the specimen is Solanum scabrum , thus settling the controversy surrounding this question. This result is particularly interesting, as the presence of S. scabrum in the Hungarian flora, has never been officially documented.

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Acta Agronomica Hungarica
Authors: R. Ahmadvand, A. Takács, J. Taller, I. Wolf and Z. Polgár

Potato (Solanum tuberosum L.) is the fourth most important food crop in the world. It is the most economically valuable and well-known member of the plant family Solanaceae. Potato is the host of many pathogens, including fungi, bacteria, Phytoplasmas, viruses, viroids and nematodes, which cause reductions in the quantity and quality of yield. Apart from the late blight fungus [Phytophthora infestans (Mont.) de Bary] viruses are the most important pathogens, with over 40 viruses and virus-like pathogens infecting cultivated potatoes in the field, among which Potato virus Y (PVY), Potato leaf roll virus (PLRV), Potato virus X (PVX), Potato virus A (PVA), Potato virus S (PVS) and Potato virus M (PVM) are some of the most important viruses in the world. In this review, their characteristics and types of resistance to them will be discussed.

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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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