The Effect of Pesticides on the Tomato Bacterial Spec Disease Pathogen _Pseudomonas Syringae_ pv. _Tomato_  
[PERSON]  
1 Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine; [EMAIL_ADDRESS] (L.B.); [EMAIL_ADDRESS] (L.P.)1 Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine; plant_path@ukr.  
of the genetic and phenotypic diversity of existing pathogens and, as a consequence, complications with identification of the pathogen, loss of resistance by varieties, and increased harm from bacterial diseases. The use of pesticides is one of the factors that increases variability of phytopathogens [6; 7; 8].  
Most pesticides used in agriculture have a wide range of effects. On the one hand, it provides the possibility of their application for the control of a wide range of pathogens and pests. On the other hand, it determines their influence on non-target organisms [9; 10; 11; 12; 13].  
Pytopathogenic bacteria in agrophotocenoses are influenced by all factors (both biotic and abiotic) that act in these ecological niches. Pesticides are one of the most important abiotic factors of agrophotocenoses. It is known that a significant proportion of pesticides act on non-target organisms and have mutagenic activity [10]. Stress caused by abiotic factors and, in particular, by the action of pesticides, induces morphological and physiological changes in bacterial cells and phenotypic heterogeneity in the cell populations of phytopathogenic bacteria [14; 15]. Scientists intensively investigated the effect of pesticides on soil microorganisms and bacteria in the plant phyllosphere [10; 16]. However, the effect of pesticides on plant pathogenic bacteria as non-target microorganisms has almost completely remained outside the attention of researchers. In particular, the mutagenic activity of pesticides relative to phytopathogenic bacteria has not yet been extensively studied. Previously, we have shown that some pesticides, which are widely used in grain crops, have mutagenic activity or cause morphological dissociation of the agent of wheat basal bacteriosis _P. syringae_ pv. _atrofaciens_[15].  
Components of the bacterial outer membrane play an important role in adaptation of gram-negative bacteria to various selective factors. Morphological dissociation, or smooth-to-rough (S-R) mutation, is a step-by-step process that results in an irreversible change [17]. The resulting R mutants are unable to revert to their original state, and often fail to survive in a host with an intact immune system. S colonies are recognised by their moist nature and are indicators of freshly isolated wild bacterial strains. R colonies are rough, dry, granulated, and mutant types of bacteria that lack most of the surface proteins including the capsule and lipopolysaccharidesaccharides. R colonies are formed by bacteria that are usually avirulent. The ability to show variations in both smooth-rough ways and from rough to smooth (R-S) colonies has also been observed in phytopathogenic bacteria. Processes of step-by-step S-R mutations are bacterial responses to changing conditions.  
The aim of this work was to determine the effect of pesticides recommended for use in tomato plantations in Ukraine on the causative agent of bacterial speck of this crop--_Pseudomonas syringae_ pv. _tomato_.