Potato cyst nematodes (PCN) collected in six localities in the Leningrad region of North West Russia were identified as Globodera rostochiensis pathotype Ro1 and were used for subsequent resistance tests. Seventynine accessions of cultivated and closely related wild potato species from the VIR collection in Russia were screened on resistance to G. rostochiensis pathotype Ro1 and on the presence of molecular markers for H1 and Gro1-4 resistance genes. No associations were detected between the resistance level of diploid and tetraploid Andean and tetraploid Chilean potato landraces (indigenous cultivars) and their related wild species and their geographical distribution or presence of PCR-based markers that are associated with the H1 and Gro1-4 genes. At the same time, all susceptible genotypes lacked such markers. New sources of resistance were found and could be used in breeding.

With 7 figures and 1 table Abstract The causal agent of potato wart (Synchytrium endobioticum) is an obligate parasitic chytrid fungus. It is included as a quarantine pathogen in 55 countries, with losses in susceptible cultivars reaching 50–100%. The aim of our study was to characterize the resistance to S. endobioticum pathotype 1 in cultivated potatoes from a well‐characterized subset of the Vavilov Institute of Plant Industry collection and to determine whether this resistance is associated with cultivated potato species taxonomy, with ploidy, with geographic distance or with a molecular marker Nl25‐1400 proposed for molecular screening for resistance to pathotype 1 of S. endobioticum. Within the diversity of 52 landrace genotypes, our work shows a lack of such predictive associations with wart resistance. High intraspecific variation of wart diseases resistance allows the selection of extremely resistant and susceptible genotypes available for future genetic and breeding studies.

A b s t r a c tA modified method of combined chemo-thermotherapy for eradication the most damaging viruses in potato plants is proposed. The materials for study included 91 clones of 85 accessions of three South-American cultivated species Solanum phureja (18 accessions), S. stenotomum (26 accessions), S. tuberosum (S. tuberosum ssp. andigenum and S. tuberosum ssp. tuberosum) (41 accessions) from the VIR field collection (N.I. Vavilov All-Russian Institute of Plant Genetic Resources). The results of ELISA for 91 clones from the field collection and RT-PCR analysis of the corresponding microplants, when introducing clones into in vitro culture, have shown that all material was infected by viruses (potato viruses Y, X, S, M and potato leafroll virus -PVY, PVX, PVS, PVM and PLRV) to varying degrees. Single infections were detected in 25.3 % of the 91 clones, and the remaining clones were multi-infected and contained several viruses in various combinations. Based on the termo-and chemotherapy protocols as well as complex therapy used in leading potato genebanks (Leibniz Institute of Plant Genetics and Crop Plant Research -IPK, Germany; International Potato Centre -CIP, Peru), we have developed a modified method of combined therapy comprising three successive cycles of in vitro plant cultivation on Murashige and Skoog basal medium (MS) supplemented with ribavirin (30 mg/l) at 37 С during 4 weeks. Between the cycles, the microplants were incubated for 2 days at 26 С on the same medium with ribavirin. Each clone was tested for the presence of viruses by RT (revers transcription) PCR before and after the combined thermo-chemotherapy. In RT-PCR, 42 clones (46 %) were completely free from tested viruses, 44 % were free from some viruses, and 10 % of the clones were unable to improve. On the whole of 91 clones, PLRV was eliminated from 72.7 %, PVY from 71.4 %, PVM from 63.9 % and PVS from 57.4 % of microplants. Differences in elimination frequency between the viruses were not significant (р > 0.05). Also, there were no significant differences in elimination of different viruses between the accessions of different cultivated species. The difference of this modification from IPK protocols (Germany) lays in simultaneous effect of high temperature (37 C) and ribavirin (instead of sequential application), and, unlike the CIP (Peru) scheme, it comprises less steps.

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