Lysak S. Early dry blight and initial material of tomato for breeding on resistance

Under conditions of North-East and Central regions of the Forest-Steppe of Ukraine there is determined the specific composition of causal organisms of tomato early dry blight and its correlation in nature population. Three species of Alternaria genus: Alt. solani, Alt. alternata (Syn.: Alt. tenuis), Alt. tenuissima and two species of Stemphylium genus: St. solani, St. bortyosum participated in the pathogenesis of early dry blight. Fungi Alternaria solani and Stemphylium solani occupied the leading place in this process. It is determined that a component of the cycle of Alternaria fungus development are conidia, as well as microsclerotia and chlamydospores. The latter, as modifications of mycelium, are the main link of the hibernating stage and the source of renewal of the infection.There was not difference of principle in two climatic regions of the Forest-Steppe in the development of main (Alt. solani) and accompanying (Alt. alternata, Alt. tenuissima, St. solani, St. bortyosum) causal organisms. Thestimulus for development of fungi of Alternaria and Stemphylium genera as ectoterm organisms was some combination of time and temperature (physiological time) and not a period of time.For the first time there were revealed, two untypical species of pathogenesis of early dry blight. This is leaves affection of varieties, F1 hybrids and lines in the form of numerous small spots with rough surface, which lie stretched in a file along veins. Zonal concentricity on spots is weakly visible. On the leaves of F1 hybrids there are revealed elongated, large, quickly drying out spots at first of light yellow and later yellow-grey colour. In the central part of spots the leaf's tissue is darker. Sporification is absent on spots.Variability of the varietals sign of tomato resistance is investigated against natural infectious background and with artificial inoculation. Statistical analysis of resistance manifestation with the use of maximum degree of affection, coefficient of stability of the resistance level, distribution of genotypes by resistance groups allowed to select effectively perspective resistance sources for breeding. From the total quality (120 pieces) there were singled out 7 samples (5.8%) as initial material.