ИСТИНА

For plants particularly harmful are mixed infections with viruses, bacteria, fungi, both during cultivation and on its way to the consumer. For example, in Russia mixed infections potatoes with viruses and viroid lead to the loss of up to 70% of the crop. We know that at a present time, potato and many other plants viral infections are incurable.The cost-effective way is diagnostics and rejection of the infected plants to prevent the spreading of the disease.As you know, correct and final one is molecular diagnostics. The molecular diagnostics of infections is a special case of the search of the targeted nucleotide sequence or the targeted antigen. In general, the molecular diagnostics does not depend on the biological nature of the pathogen and the organism, only the method of preparation of a sample for analysis is changed. We used ELISA, Immuno dot-blot, DNA probes, PCR, Low- density DNA-chip and Immunochromatography methods for diagnostics of the virus and viroid infections of the seed potato varieties of the Central collection of Russian Federation in collaboration with the Lorh Research Institute of Potato Farming. Among immunodiagnostic methods Lateral Flow Immunoassay (LFIA), in other words, immunochromatography assay (IChA), has a special significance because the tool for analysis is the test-strip with the size 0.5x7-8 cm. The result of the analysis is determined by eye due to staining of the analytical zone in the "yes-no" way in comparison with the internal controls. Therefore this tool can be used for field diagnosis by unqualified personnel. The analysis takes 5-15 min, so this is express-method. IChA has comparable sensitivity with the laboratory ELISA. The sensitivity of IChA is quite sufficient for the diagnosis of the systemic virus infection. This method is convenient for mass diagnostics in the field, particularly in emergencies epiphytotic, epizooty, and pandemics. Field testing was conducted for 360 baseline clones of 28 varieties of seed potatoes from the Bank of Healthy Potato Varieties in the Arkhangelsk region The rate of agreement of ELISA and ICha of the PVX infection was 98.8% (see Table). In total, 360 clones of potatoes were analyzed, and PVX was identified in 23 clones. More than 3000 test have been made to analyze the infestation of the central collection of Russian potato with viruses X, Y, PLRV, S and M together with the MSU company "Immunotech". Matching of detection results of potato viruses by ELISA and immunochromatography test-system (IChTS, LFIA) was 89% for virus Y and 100% for virus X; for healthy plants, the results coincided by 100%. However, common LFIA are limited by the maximum number (approximately five) of different substances that can be analyzed simultaneously using a single test strip. The simultaneous detection of multiple analytes in biosamples has gained increasing significance over the last several years, especially for detection based on highly specific and affine immune interactions. Six potato virus and two bacterial infections were discovered simultaneously on one test strip by our colleagues from the Bach Institute of Biochemistry of the Russian Academy of Sciences. Two-stage approach was used as economically expedient for mass analysis of the mass initial seed material. At the first stage, an efficient and available even under field conditions express method of diagnostics was applied, i.e. the immunochromatographic method on test strips to reject clearly infected material. At the second stage, the analysis of remaining plants is to be made either by ELISA or by an available version of RT-PCR. Such seed material having passed two-stage selection is liable to multiplication and guaranteesa high yield in the field under suitable conditions. Recommendation from the lab to the seed-growing (Russian) farms: The annual diagnostics of potato infections should be made both at the stage of production of pre-basic material (test-tube plants, scions, micro tubers) and under field conditions to select healthy plants. Such seed material having passed two-stage selection is liable to multiplication and guarantees a high yield in the field under suitable conditions