Distribution and biological features of tomato viral diseases in the agrocenoses of Ukraine

The purpose of the work was to analyze the present distribution of viruses that infect tomatoes and to identify the species composition of the tomato viruses under field conditions in Ukraine, as well as to test commercial seeds of various tomato varieties for the presence of viral contamination. In this work, a range of methods, which included visual diagnostics, various modifications of enzyme-linked immunosorbent assay, electron microscopy method and the method of statistical data processing were used. A number of symptoms of viral etiology were detected by visual diagnostics. Symptoms of viral etiology on plants were displayed as necrosis, chlorosis, yellow-green mosaic, dark green vein mosaic, and on fruits as ring-shaped spots, various fruit deformations. The morphological properties of the studied viruses were researched by electron microscopy. As a result, two types of virions were detected. The first type of virions was spherical, with a mean diameter of 29 nm. According to the literature, such shape and diameter of the virions are characteristic of the Cucumovirus genus members, in particular the cucumber mosaic virus. The second type of virions was rod-shaped, with a mean length of 300 nm and a mean diameter of 15 nm. According to other researchers, such morphological features are characteristic of the tobacco mosaic virus. The results of five-year monitoring of agrocenoses of Ukraine found that recently in a tomato crop circulates 5 species of viruses, namely tomato spotted wilt virus, cucumber mosaic virus, tobacco mosaic virus, potato virus X, and tomato mosaic virus. We also tested the seeds of 25 varieties of tomatoes by enzyme-linked immunosorbent assay for the presence of viral contamination. The tests revealed that 37% of tested tomato seeds were contaminated with viral antigens. Viral antigens found in tested tomato seeds were antigens of three species of viruses, namely tobacco mosaic virus, cucumber mosaic virus, tomato mosaic virus. In general, the tomato seeds were contaminated with mono-infections, except for mixed infection of cucumber mosaic virus and tomato mosaic virus that was detected once.