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Periodica Mathematica Hungarica
Authors:
A. Hajnal
,
P. Turán
, and
I. Juhász

In this column Periodica Mathematica Hungarica publishes current research problems whose proposers believe them to be within reach of existing methods. Manuscripts should preferably contain the background of the problem and all references known to the author. The length of the manuscript should not exceed two doublespaced type-written pages.

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Large numbers of genetically stable, homozygous plants are needed for classical and molecular breeding programmes. In vitro anther culture has proved to be a useful tool for haploid/doubled haploid (DH) induction in pepper (Capsicum annuum L.) for more than twenty years. The present paper reports on a great improvement in the in vitro haploid induction and genome duplication methods routinely used for resistance breeding in sweet and spice peppers by two Hungarian research institutions, the Agricultural Biotechnology Center in Gödöllő and the Budapest Research Unit of the Vegetable Crops Research Institute. As a result of the colchicine-stimulated early genome induction method, the critically low (<0.1%) regeneration frequency of spice pepper types became ten times greater, reaching a value of around 1.0%, though this was still considerably lower than that achieved in pepper varieties for fresh consumption (5-10%). Moreover, the ratio of useful doubled haploids was far higher (H:DH = 1:2 or 1:4) in some cases after colchicine treatment than that of untreated control plants (H:DH = 2:1 or 3:1, depending on the genotype). An efficient method with good reproducibility, requiring less manual work, was elaborated for the in vitro genome duplication of pepper haploid regenerants using colchicine. When the haploid induction ability of plants conventionally cultured in the greenhouse was compared to that of plants raised under artificial conditions in phytotron chambers (satisfactory day and night temperatures, illumination, humidity), the responsiveness of the latter microspores (ratio of plant regeneration) was found to be almost twice as high. The application of 3% maltose for six days at 35°C resulted in a 1.45% increase in the ratio of responding anthers and a 0.34% increase in plant regeneration, averaged over all the variety types. Phenosafranin staining was used for the analysis of microspore viability. The reduction in viability during the induction period proved to be less pronounced in lines with better androgenetic responses than in those with poorer responsiveness.

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Mutations in the HIV-1 genes associated with resistance to antiretroviral drugs were detected also in primary HIV infected individuals who did not receive antiretroviral treatment. Drug resistance genotyping of HIV pol gene was done by in situ DNA hybridization using a Line Probe Assay and by direct sequencing. Viral variants harbouring resistance mutations such as: M41, T69R, K70R, M184V, T215Y in the pol gene were detected in 14% of the subjects. HIV mutants resistant to NRT inhibitors were found in 10 and 20% of patients infected before and after the year 2000, respectively. Multiple drug resistant viruses (2–3 drug classes) were present in 3.5% of the mainly recently infected patients. In protease gene only minor resistant mutations were found such as L10I and A71V.These findings indicate the evolution of drug resistance showing a correlation with the time of introduction of combination therapy in our country, where more than 70% of HIV infections were by homo/bisexual transmission.This confirms the transmission of drug-resistant HIV shown by genotype testing during primary infection in therapy-naive patients and initiates serious clinical and public health consequences.

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As locus-specific co-dominant PCR-based markers that allow semi-automated, high-throughput investigation technologies, microsatellites are ideal tools for genotype identification. Eleven of a set of 114 microsatellite markers available at the Agricultural Biotechnology Center proved to be suitable to distinguish between the parents of at least one of nine sweet pepper hybrid combinations. Markers with the highest information capacity were found to be capable of distinguishing between the parents of four different hybrid combinations and exhibited up to four different alleles in 18 haplotypes.

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