Relevance. Alternaria dauci, Alternaria radicina and Fusarium oxysporumare wide spread and harmful fungal diseases of carrot (Daucus carota L.) in the Russian Federation and in the world. Total losses of roots from these diseases are 35-70%. Obtaining of new varieties and hybrids resistant to these pathogens is complicated by the fact of polygenic control resistance traits to fungal diseases of Alternaria and Fusarium genus. Interaction of polygenic resistance traits with environmental factors causes the soft character of changing these traits: effects of interactions between alleles and genes are changed, the dominant effect become weaker, additive effect become stronger. So, we can say about of the tolerance to complex pathogens for that case.The goal of our study is to determine the heritability of tolerance to fungal pathogens Alternaria dauci and Fusarium oxysporum by hybrids F1 of carrot.Materials and methods. Materials of studies were 7 basic lines with different types of roots; 7 prospective hybrids F1 and mycelium of Alternaria dauci and Fusarium oxysporum with spores (for inoculation). Methods of studies were: evaluation resistance of lines and hybrids F1 (seedlings, adult plants and roots) at different types of infection backgrounds; dispersion and correlation analysis. Resistance the basic lines of carrot to fungi of Alternaria and Fusarium genus was evaluated step-by-step, using several types of artificial and natural infection backhybrids F1. Tolerant samples were selected and they were used in crossings. F1 – hybrids have been obtained and they have been evaluated at artificial and natural backgrounds.Results: 1. One tolerant male form № 1268 and 6 female forms with weak sensitivity to fungi of Alternaria and Fusarium genus were selected from basic material. They were used in crossings. hybrids F1 have been obtained. 2. Analysis the heritability of carrot resistance to fungal pathogens Alternaria dauci and Fusarium oxysporum identified, that such type of resistance inherited by father’s type. 3. Using tolerant carrot line № 1268 in crossings as the male form and 6 female forms with weak sensitivity to fungal pathogens Alternaria dauci and Fusarium oxysporum increased significantly the percent of tolerant plant in 3 F1 – hybrid population under artificial infection on provocative infection background.

Relevance. Tomato root rot is a complex disease caused by a variety of soil-borne fungal pathogens, among which Fusarium oxysporum, F. solani and F. gibbosum occur with the greatest frequency in the conditions of the Republic of Moldova. The originality of the work consists in identifying the differentiated influence of pathogens of Fusarium root rot and temperature on the variability and heritability of the organs of growth and development of tomato plants.Material and methods. Two varieties and 3 lines of tomatoes with good economically valuable characteristics were used as material for the study. To test the response of plants to pathogens of fusarium root rot, we used culture filtrates of 6 – F. oxysporum isolates, 6 – F. solani, and 4 – F. gibbosum, prepared in a standard liquid Czapek medium. The plants were grown at the optimum temperature (23...24°C) and with alternating temperatures of 23...24°C and 10...11°C for two days each. Seed germination and root length were used as indicators of growth and development. The genetic parameters of the variability and heritability of the studied traits were studied.Results. An analysis of the reaction based on seeds germination and root growth showed its significant differentiation in the tomato genotype x type of fungus x isolate of the fungus x temperature system. A factor analysis of the interaction of the tomato genotype x Fusarium fungus revealed a significant role of the plant genotype in response to the pathogens. A significant effect of Fusarium fungi and temperature on the genetic and phenotypic variance of signs of growth and development of tomato plants, heritability in a broad sense, genotypic and phenotypic coefficient of variation, and genetic progress have been established. It is concluded that it is advisable to use the reaction of signs of growth and development of tomato to Fusarium pathogens in order to identify genotypes with good inheritance of the resistance trait.

Relevance. In the Republic of Moldova in recent years, during tomato flowering, air temperature reaches 35°С and higher, which significantly reduces fruit set, yield and product quality, therefore, the creation of varieties resistant to temperature stress is of particular importance. The relevance of the studies is due to the need to identify tomato genotypes resistant to high temperatures, to identify the genetic nature of the variability and degree of inheritance of tomato growth organs when interacting with different temperature conditions. The purpose of the research is to determine the effect of stress temperatures on the organs of growth and development of tomato plants at an early stage of ontogenesis, the degree of genetic, phenotypic variation and inheritance of characters. Materials and methods. The research material was 5 promising lines of tomato with high economically valuable traits. As a standard, a omologated variety Mary Gratefully was used. Four temperature levels were used – optimal (25°С) and stress (38, 40 and 42°С). The length of the germinal root and stem of 7-day-old plants was measured. The experiment was made in 3 replicates. The following were studied: genetic and phenotypic variants, heritability coefficient, phenotypic and genotypic coefficients of variation, genetic progress. The data were processed in the STATISTICA 7 software package. Results. As a result of the studies, a significant differentiation of the reaction of tomato genotypes to temperature stress was revealed. A significant effect of temperature on the genetic and phenotypic varieties of signs of growth and development of tomato plants, heritability in the broad sense, genotypic and phenotypic coefficient of variation, and genetic progress have been established. Of a great interest for further studies are the Mary Gratefully, L 304, L 306 genotypes, which are highly resistant to the studied traits.