The potato disease pathogens are one of the main factors that reduce the marketability of tubers and cause great losses during  transportation and storage. The placement of nonstandard products in storage in autumn leads to significant losses in spring. Therefore, the reducing of the number of pathogenic organisms on potato tubers during the growing season is an important problem.

The use of microbiological preparations in the modern technologies not only increases the plants resistance to phytopathogens, their productivity and quality, but also contributes to the recovery of the agrocoenosis from the harmful effects of the chemicals. The fixation of atmospheric nitrogen, the production of biologically active substances, activation of root ability to absorb the nutrients, biocontrol of phytopathogens and the induction of the systemic plant resistance are the mechanisms of the positive influence of the associative rhizosphere and endophytic bacteria on plants. The impact of the microbiological preparations on the potato contamination by the pathogens during the potato (Solanum tuberosum L.) tubers storage has been understudied. The study of the special aspects of the microbial community activities during the storage of the potato tubers, grown in the western forest-steppe zone, the impact of abiotic and agrotechnical factors, use of Planryz and combination of Planryz + Diazofit + FMB was the aim of research. The comparative ratio assessment of bacteria, actinomycetes, phytopathogenic and saprophytic fungi of the epiphytic microflora on the potato tubers in case of biological preparations use was the task.

The study was conducted during 2009-2013 at Zhovkivskyi district (western forest steppe zone in Lviv region).
The following biological preparations were studied: Planryz, based on Pseudomonas fluorescence strain AR-33 (2.0 l/ha), Diazofit (the active ingredient - bacteria Agrobacterium radiobacter, 0.2 l/ha), Fosforoenteryn – a biological preparation based on phosphorus bacteria Enterobacter nimipressuralis 32-3 (FMB- fosforomobilizator 0.2 l/ha). Fitotsyd (based on Bacillus subtilis,
1.0 l/ha) was used as the biological control, Rydomil Gold MTS68 WG, 2.5 l/ha – as the chemical one. The tubers were treated by the preparations before planting, storage and the plants themselves during the budding. The trials were conducted on the 1st term
(27-30 April), 2nd (12-15 May). The method of consequent suspension dilutions  (off-washings from the tuber surface), cultivation for the elective nutrient medium, consequent enumeration of the colonies that grew on them, the study of the morphological and cultural properties of the selected isolates were used to study the tubers microflora at the beginning and end of the storage period. The statistical analysis of the data obtained was processed with the help of the computer program Excel.

Analysis of potato tubers at the beginning and end of the storage period showed that the use of Planryz and Planryz +Diazofit + FMB reduced the level of the tuber contamination with the pathogens Fusarium and Alternaria sp. compared to the control group. At the beginning of the storage in the first planting period in the breed Lileya the control figures were 4.2-4.8; under the biological preparations treatment – 1.2-3.6; under the chemical fungicide Ridomil Gold treatment – 3.8-4.3 × 10³ CFО/ sm². At the end of the storage period they were 6.4-7.3; 2.7-3.8 and 5.9-6.1 × 10³ CFО/ sm² respectively. The similar tendency was observed in the tubers of  Skarbnytsia breed (at the beginning of the storage period – 1.2-1.5; 0.4-0.7 and 1.0-1.3 × 10³ CFО/ sм², and at the end – 2.1-8.7;  0.7-3.6 and 1.1-4.8 × 10³ CFО/ sm²). The pathogen contamination level increased at the second term of planting the tubers and treatment with the biological preparations contributed to the reduction of the diseases during the storage period in comparison with the control group. The number of pathogens Fusarium and Alternaria sp. Being reduced in 1.5-4.7  times was observed at the beginning and the end of the storage period in the tubers epiphytic microflora of relatively resistant breed Skarbnytsia in comparison with the relatively susceptible Lileya (on the average relatively 0.7-3.0 × 10³ CFО/ sm² against 3.3-4.5 × 10³ CFО/ sm²). This can be explained by the fact that in the relatively resistant plants, the secondary plant metabolites (phenolic compounds, alkaloids, terpenes, etc.), the protective stress-relieving components can modify metabolism, induce the changes of the plasticity breeds and their level of resistance to pathogens. The combined use of Ridomil Gold and Planriz was more effective than the use of the fungicide (on the average the number of pathogens reduced in 1,1-1,3 times in the tubers epiphytic microflora during the storage in comparison with one- fungicide treatment).

Bacteria, which are the basis of biopreparations, produce phytohormones, have the ability to nitrogen fixation, improvement of hydro-mineral plant nutrition, inhibit the development of pathogens due to the bactericidal or fungicidal production of the substances, and their immune-stimulating activity has a prolonged effect, helping to preserve the protective potential in potato tubers during the storage period.

The pre-planting tuber treatment, further plant spraying during the vegetation period and pre-storage treatment with the biopreparations Planryz, Diazofit, Fosfoenteryn reduce the population density of the pathogens Fusarium and Alternaria in the tubers epiphytic microflora in 1.9-2.8 times compared to the controlgroup. The reduction in 1.5-4.7 times of the pathogen number in the tubers epiphytic microflora in the relatively resistant breed Skarbnytsia at the beginning and end of the storage period in comparison with the relatively receptive Lileya was established. The combined use of Ridomil Gold and Planriz contributed to the fungicide effect. In the future, we plan to continue the study of the induced resistance of the plants Solanum tuberosum L. against the pathogens under the treatment with microbiopreparations.

Key words: Solanum tuberosum L., epiphytic microflora, biopreparations, storage.