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The way of inheritance, the manifestations of heterosis, transgression and depression, minimal number of genes by which parental forms differ, degree of dominance, manifestations of epistasis and coefficient of heritability and efficiency of selection with regard to plant height and number of leaves, on Burley tobacco samples are established. For the purpose are researched the population of P1, P2, F1 and F2 of seven hybrid combinations. The results show that in the height of plants and number of leaves inheritance is preferably overdominantly and always in the direction of the parent with the higher values of investigated parameters. With respect to the height of the plants was observed and incompletely dominantly, and when the number of leaves and an additive. Manifestations of heterosis and transgression are more pronounced in relation to the number of leaves and have significant values of economic importance, only by this indicator. Data from hybridological analysis showed that the minimal number of genes determining the expression of the trait plant height is greater than the number of leaves. Epistatic interactions are more strongly manifested in the determination of the trait height of plant, but only in the number of leaves negative ones are observed. The relatively low to medium values obtained in terms of the coefficient of heritability in the studied crosses Burley tobacco show that a low share of genotype influence on the manifestation of the studied trait is observed, which means that the selection for plant height will be more effective in the later hybrid generations. The established even lower values for the index number of leaves show the crucial importance of the influence of the environment on the determination of the trait and suggest an effective selection in even later hybrid generations, which makes the selection activity difficult. The study shows that, in general, the selection for the trait number of leaves is more complex and longer than that for the height of the plants. [ABSTRACT FROM AUTHOR]

Background. Barley is an ancient crop currently cultivated in more than 100 countries. High adaptability makes it possible to cultivate it in environments unfavorable for many other crops. At the same time, fungal diseases can have a negative impact on its grain yield and quality. One of the most harmful is the fungus Blumeria graminis (DC.) Golovin ex Speer f. sp. hordei Marchal. The pathogen can overcome a cultivar’s resistance, resulting in significant harvest losses. There is a need for a constant search for new effective sources of resistance to powdery mildew for barley breeding.Materials and methods. A set of 950 barley accessions from the East Asian center of the crop’s morphogenesis were studied at the adult stage of plant development. They were screened and crossed in the fields of Pushkin and Pavlovsk Laboratories of VIR (St. Petersburg, Russia). Genetic control of barley resistance to B. graminis was analyzed in a climate chamber under artificial infection pressure with the northwestern population of the fungus. Scoring scales were used for screening.Results and conclusions. Weak development of B. graminis during the heading phase was observed on plants of 38 barley accessions from the East Asian center. High resistance at all stages of development was manifested by 20 genotypes that can be used in breeding programs. Resistance genes in 18 selected forms differed in their effectiveness at the seedling stage of development and during the heading phase. Accessions k-3433, k-10931, k-10934, k-11608, k-17545, k-20272, k-20279, k-20354 and k-27867 had one dominant resistance gene each. Accessions k-11608, k-12278, and k-17545 are protected by the identical gene, while the resistance of k-3433 is induced by a gene that differs from the genes present in accessions k-10931 and k-20279.

The way of inheritance, the coefficient of heritability, the manifestations of heterosis, transgression and depression in terms of the length and width of the leaves in hybrid combinations Burley tobaco are established. For that purpose are studied, the Р1, Р2, F1 and F2 populations of eight crosses Burley tobacco. The obtained results suggest that inheritance of the length or leaves is overrdominantly, incompletely dominantly or additive, and of the width of leaves is incompletely dominantly and overrdominantly,, as in both indicators it is always in the direction of the parent with higher values. Manifestations of heterosis and transgression are of economic importance only in terms of leaf width. The minimal number of genes that control the expression of the studied indices is small and uniform and the length and width of the leaves. The phenotypic expression of leaf size is strongly influenced by negative epistatic interactions, especially pronounced at their width. The established medium to higher values of the coefficient of heritability of the length of the leaves are an indication of a relatively equal share of influence of genotype and environmental conditions on the phenotypic manifestation of leaf length, which suggests that the selection on this indicator to be effective in earlier hybrid generations. The selection of width of the leaves will be effective in later hybrid generations due to lower values coefficient of the heritability, for this indicator. This shows that the coefficient of heritability and the related coefficient of efficiency of the selection is different in both indicators, making it difficult selection work. [ABSTRACT FROM AUTHOR]

The way of inheritance, the coefficient of heritability, the manifestations of heterosis, transgression and depression in terms of the height of the plants and the number of leaves in hybrid combinations Burley tobaco are established. For that purpose are studied, the Р1, Р2, F1 and F2 populations of eight crosses Burley tobacco. The obtained results suggest that inheritance of the height оf plants is overdominantly or incompletely dominanlyt, in the direction of the parent with both higher values and lower values. Inheritance of the number of leaves is overdominant in the direction of the parent with higher values, or incompletely dominant in the direction of the one with lower values. The manifestations of heterosis and transgression are of economic importance only in terms of the number of leaves. The minimal number of genes controlling the manifestation of the studied indicators is higher at plant height than the number of leaves. Due to low to medium values of the heritability coefficient obtained for both indicators, it is found that the environmental conditions have a stronger influence than the genotype on the manifestation of the traits plant height and number of leaves This suggests an effective selection in later hybrid generations for both studied parameters. The direction of hybridization influences the inheritance of the height of plants and the number of leaves. [ABSTRACT FROM AUTHOR]

Background. One of the most harmful diseases of barley in all areas of its cultivation is scald. The causal agent Rhynchosporium commune Zaffarano, B.A. McDonald & A. Linde (formerly – Rhynchosporium secalis (Oudem.) J.J. Davis) is characterized by a high level of variability, which leads to the emergence of new pathotypes and the loss of resistance of a number of cultivars. Most barley cultivars recommended for cultivation are highly affected by the pathogen. The aim of the study was to find new donors of effective barley resistance genes to R. commune.Materials and methods. Resistance to the fungus was tested in 99 accessions of barley landraces from 18 countries under laboratory and field conditions. The experiments employed isolates and clones of R. commune isolated from plants collected in Leningrad Province. Plant resistance was scored using point scales. Genetic control of fungal resistance was studied in the selected accessions using hybridological analysis.Results and conclusions. We identified 3 accessions of barley landraces, which retained high resistance to the fungus for six years of study in the field under inoculation with different populations of R. commune. Accessions k-31504 (Macedonia), k-31505 (Ethiopia) and k-31503 (India) are protected by R. commune resistance genes, which differ from each other, are not allelic to the previously identified effective Rrs9 gene, and manifest themselves throughout all stages of barley ontogenesis. Each of accessions k-31504 and k-31505 incorporates 2 recessive pathogen resistance genes; k-31503 carries 3 recessive resistance genes.

In conditions of vegetative trial carried out against selective backgrounds in 2017-2019 the response of 27 flax samples to a decrease in soil acidity to neutral pHKCl was studied. The scheme of the experiment was as follows: variant I (control) − pHKCl 5.3-5.5, P2O5 − 320-340 mg/kg, K2O − 81-92 mg/kg; variant II − pHKCl 6.2, P2O5 − 312-345 mg/kg, K2O − 84-98 mg/kg. It has been shown that during the «herringbone» phase in the majority of studied flax genotypes against the background of pH 6.2, the symptoms of “physiological oppression” of flax were observed: small spots developed on the upper leaves, the plants stopped growing, the stems thickened, and the tops of severely affected plants died off. As a result, at the beginning of the growing season at plant height of 7-10 cm, most of the samples were severely affected (from 69 to 100 %). The exceptions were varieties of fibre-flax Hermes (France), Vega 2 (Lithuania), Atlant (Russia) and linseed genotypes No. 3896 (Russia) and Norlin (Canada), which had a weak and medium degree of affection (8.3-45.5 %). Moreover, these genotypes showed a high level of both biological (75-90 %) and agronomic (77.3-85.6 %) resistance in the phase of "early yellow ripeness". The identified flax collection samples can be used as sources of resistance to flax «physiological oppression» caused by stressful edaphic factors in a neutral environment. On the basis of the analysis of the main elements of fiber productivity in studied flax genotypes, it has been established that against the background of pH 6.2 the reduce in plant height was from 11.4 to 52.1 % relative to the control, weight of the technical part of the stem − from 7.2 to 83.4 % , fiber mass − from 9.6 to 85.1 %. For the first time, on the basis of hybridological analysis, an assumption was done as to the pres-ence of a strong dominant gene, controlling the resistance to high soil pH values in the Hermes (France) flax variety and the linseed line No. 3896 (Russia).

The character of inheritance, inheritability coefficient, and expressions of heterosis transgression and depresion referring to the length and width of the leaves in Burley tobacco are established. For this purpose, were investigated populations of Р1, Р2, F1 a nd F 2 of seven hybrids Burley tobacco, involving local and introduced varieties. Results showed that in a hybrid combination inheritance of the length and width of leaves is overdominantly or semidominantly and always in the direction of the parent with the higher values of research sign. In the explored options large leaf tobacco Burley, the manifestations of heterosis and transgression are no economic importance. The minimal number of genes affecting the expression of sizes of leaves is small and does not vary in different crosses. Manifestation of negative epistat interactions makes very difficult selection on the sizes of the leaves especially their width. Obtained are low values of the coefficient of heritability in width of leaves and medium ones in lenght of leaves, indicating that selection of size the leaves will be effective in later hybrid generations. [ABSTRACT FROM AUTHOR]

Background. Scald (caused by Rhynchosporium secalis (Oudem.) J.J. Davis) is one of the most harmful barley diseases. The pathogen is characterized by the differential interaction with the host plant genotypes. Therefore, the most rational plant breeding strategy should envisage broadening of genetic diversity of cultivated varieties. It has been found that the majority of the recently released barley varieties and of the previously identified sources of resistance to R. secalis are now susceptible to the pathogen. Only the resistance gene Rrs9 maintains efficiency against the pathogen populations in the Russian Northwest. Earlier, we have found scald resistant barleys to be frequent among barley landrace accessions. It was demonstrated by the hybridological analysis that accessions k-3307, k-15868, k-18989 and k-3481 are protected by effective scald resistance genes that differ from each other, and which are not allelic to the Rrs4, rrs6, rrs7 or Rrs9 genes. The goal of the present work was to study genetic control to the dangerous pathogen in four other barley landraces.Materials and methods. The inheritance of scald resistance was analyzed in barley accessions k-16233, k-27205 (China), k-27768 (India) and k-22299 (Ecuador). The study employed two experimental techniques, that is, the pathogen/host plant differential interactions analysis in the lab, and the hybridological analysis in the field. The experiments were carried out using R. secalis isolates and clones from the pathogen populations sampled in the North Caucasus and the Russian Northwest. Resistance was scored against the scales from 0 (no symptoms) to 4 points (in the lab), and from 0 to 5 points (in the field). Plants that scored 0-2 points were regarded as resistant.Results and conclusions. The analysis of the pathogen clone/host plant interaction has shown that the landraces k-16233, k-27205 (China), k-27768 (India) and k-22299 (Ecuador) are protected by effective genes of scald resistance which differ from each other and are non-allelic to the previously effective genes Rrs4, rrs6, rrs7 and the currently effective Rrs9. According to the hybridological analysis data, k-27205 has one dominant gene of scald resistance; k-16233, k-27768 and k-22299 are protected by two dominant effective resistance genes, all of which manifest themselves at all the stages of plant ontogenesis.

Studied are the inheritance, coefficient of hereditability and of the teams, the minimal number of genes and the manifestations of transgression and heterosis in terms of length and width of the leaves of mid harvesting belt in Burley tobacco. For this purpose are investigated populations P1, P2, F1 and F2 seven hybrid combinations. Data from the hybridological analysis showed that studied of us options, inheritance of length and width of leave is overdominantnly and always in the direction of the parent with the higher values of the studies index. Manifestation of heterosis and transgression are relevant only on the width of the leaves. Are established very few and negligible variations in genes influencing determines the size of the leaves. Obtained low values for the coefficient of heritability, which is why the selection by signs a length and width of the sheet 13 to 14 will be effective in later hybrid generations. [ABSTRACT FROM AUTHOR]