Purpose. To analyze the divergence of early maturing source material of corn Zea mays L. in heterosis breeding for the genetic base formation at the State Institution the Institute of Grain Crops of the NAAS of Ukraine. Methods. Field (comprehensive assessment of morphobiological and economically valuable characteristics of the source material and maize hybrids) individual selection, cumulative and recurrent selection, backross and testcrosses bree­ding methods; laboratory; analysis and synthesis; statistical. Results. The results of research on the analysis of the divergence of early maturing corn source material in the conditions of the Steppe of Ukraine has become a developed harmonized working collection of corn breeding samples adapted to the stressful conditions of this region. The gradual cyclical improvement of the lines made it possible to form the core of the genetic diversity of FAO 150–290 early maturing specimens of the southern ecotype, which are competitive in heterosis breeding. The complexity of breeding for early maturity in the steppe conditions is due to the lack of material adapted to the stress factors of the South of Ukraine. The available early maturing lines of the world collection F2, F7, Ер1, Ма21, Ма23, Со125, Со255, См7, PLS61, S72, etc., were distinguished by high cold resistance, good starting plant development, intensive accumulation of dry matter during ripening, but not adapted to the deficiency of moisture in the soil and high summer temperatures. According to the results of the experiment, it was revealed that, in terms of breeding, lines of Lancaster plasma (DK427 and DK633) were the most plastic, due to which a number of new mid-early lines were obtained, for example DK2/427, DK267, DK266/417, DK633/266, DK296, etc., which were included in the registered hybrids. Formation of the genetic base of early maturing maize source material for heterosis breeding and systematization accor­ding to different breeding characteristics provided a balance of samples of alternative components, which will be further used to model heterosis hybrids in the early maturing group. Conclusions. The updated basic collection of lines is represented by the samples of plasma Iodent: DK744SVZM, DK216SVZM, DK4173SVZM, DK235zS, DK257zM, SV, DK365SVZM, DK777ZMSV, DK733-7zM,SV, DK315SVZM; Lancaster: DK296zS,VM, DK633/266zS,VM, DK2965ZSZM, DK2953 ZSZM, DK3023 ZSZM, DK236zS,ZM; Raid (SSS): DK232MV, DK2323MV, DK239MV; Mixed: DK253ZSZM, DK273MV, DK272zS, DK281SV, DK233zM,SV, DK959MV, DK9527 ZSZM, DK247MV, DK2442MV, which is the basis of the genetic diversity of early ripening corn samples included in the State register of plant varie­ties suitable for dissemination in Ukraine.

A stabilizing (directed) selection has created a donor of short stem for winter rye (Secale cereale L.), plant height of which ranged from 50 to 60 cm. The plant height kept symmetry of its distribution curve and the frequency accumulation in central classes (positive excess). For the first time a symbolic designation to new short-stem related Hl-2Hl-2 allele and the donor name (Gnome 2) were proposed. 28 years of stabilizing selection showed that 57% of overall genetic variability of plant height resulted from adaptive genes available for directed selection by phenotype, and 43% from dominant and epistatic factors that predetermines the expression heterosis effect. Gnome 2 donor proved to have genetic additive correlation between the pants height and number of flows per ear, ear length, weight of seeds per plant , 100 seeds weight per plant; to have reverse correlation with ear density seeds weight per ear. The height of original parent components have displayed direct additive correlation with number of flowers per ear and reverse with the ear density. The additive correlation component directly exposes «genuine» impact of parental plants on the expression of the characteristics indicated among the offspring Productive bushing of parental plants, seed weight per plant directly, and seed size (100 seeds weight) indirectly, respectively, influence the height of offspring pants. The reverse additive correlation between the parents height and 100 seeds weight in the offspring is caused by pleiotropic effect of the genes impact thus enabling to combine the desirable characteristics in one genotype. Productive bushing is by 54% due to the impact of general genetic factors among the above, in particular, 30% due to that additive, 24 due to non-additive factors. The concept of genetic improvements for productive bushing of the Gnome 2 rye implies utilization of additive effect through the directed selection, as well as application of breeding techniques for controlling the effect of heterosis caused by the genes of dominant and epistatic impact. The selection paradigm requires simultaneous genotypes selection with immediate examination of the selection results by offspring while in parallel to develop inbred lines, combining these afterwards evaluating general and specific combining ability by productive bushing. It is also to be noted that the productive bushing essentially depends on the environmental conditions, which significantly corrects the implementation of productivity potent, thereby the issue of agronomical conditions aimed at extending the expression of characteristic in question remains.

Purpose. To reveal breeding and genetic peculiarities of modern spring barley varieties for the “number of grains per main ear” trait and identify genetic sources of increased combining ability for involving in hybridization. Methods. Investigations were carried out at the V. M. Remeslo Myronivka Institute of Wheat of NAAS of Ukraine. Modern varieties of domestic (‘Virazh’, ‘Talisman Myronivskyi’, ‘Komandor’) and foreign (‘KWS Aliciana’, ‘KWS Bambina’, ‘Zhana’, ‘Explorer’) breeding were involved in crossing for a full (7´7) diallel scheme. Parents and F1 were studied in field conditions during 2014–2016. Results. The analysis of variance of combining ability has shown a significant advantage in varying of general combining ability (GCA) effects. The mean square of specific combining ability (SCA) was significantly less than the GCA, but reliable throughout the years. The reciprocal effect was reliable only in 2014. Stably high effects of GCA during all years of investigations were noted in the varieties ‘KWS Aliciana’ (1.18–1.62) and ‘Virazh’ (1.33–1.48). The variety ‘KWS Bambina’ was characterized by lower but reliable positive effects of GCA (0.43–0.99) as compared to mentioned above. Non-allelic gene interaction was not found, that allowed to calculate the basic parameters of genetic variation. During all years of investigations, dominant effects of genes (H1 and H2) prevailed over the additive (D) ones in phenotypic expression of grain number per main ear. Mean degree of dominance in the experiment (H1/D) has shown overdominance. The same pattern was also distinctive for the index of mean degree of dominance in the loci . The dominance was reliably directed. Dominant effects of genes increased grain content, and recessive ones reduced it. At least 3–4 genes (groups of genes) have been revealed which determined the effects of dominance. At the same time, recessive genes (F<0) or gene effects were prevailed quantitatively in the varieties investigated. A high coefficient of heritability in broad sense (H2 = 0.98) has shown a significant determination of phenotypic variability with genetic factors. The coefficient of heritability in narrow sense (h2 = 0.66–0.68) confirmed that despite the advantage of dominant effects over the additive ones, the contribution of the latter was also significant. Conclusions. The prevalence of dominant effects of genes in the phenotypic expression of the number of grains per main ear causes the need for sufficient sample size of hybrid material and points to the expediency of conducting a more “rigid” selection for phenotype in later generations. At the same time, the considerable contribution of additive effects and high values of heritability indices give reason to predict the efficiency of selections aimed at increasing the trait in created hybrid material. The varieties ‘Virazh’, ‘KWS Aliciana’, ‘KWS Bambina’ should be used as effective genetic sources to increase grain content in combination breeding.

Purpose. To review publications relating to the key point of the genotyping technology that is competitive allele-specific polymerase chain reaction (which is called now Kompetitive Allele Specific PCR, KASPTM) and its use in various genetic-breeding researching (a study of maize). Results. The essence of KASP-genotyping, its advantages are highlighted. The requirements for matrix DNA are presented, since the success of the KASP-analysis depends on its qua­lity and quantity. Examples of global projects of plant breeding for increasing crop yields using the KASP genoty­ping technology are given. The results of KASP genotyping and their introduction into breeding and seed production, in particular, for determining genetic identity, genetic purity, origin check, marker-assisted selection, etc. are presented using maize as an example. It is demonstrated how geno­mic selection according to KASP genotyping technology can lead to rapid genetic enhancement of drought resistance in maize. Comparison of the effectiveness of creating lines with certain traits (for example, combination of high grain yield and drought resistance) using traditional breeding approaches (phenotype selection) and molecular genetic methods (selection by markers) was proved that it takes four seasons (two years in case of greenhouses) in order to unlock the potential of the plant genotype using traditional self-pollination, test-crossing and definitions), while using markers, the population was enriched with target alleles during one season. At the same time, there was no need for a stress factor. Conclusions. KASP genotyping technology is a high-precision and effective tool for modern genetics and breeding, which is successfully used to study genetic diversity, genetic relationship, population structure, gene­tic identity, genetic purity, origin check, quantitative locus mapping, allele mapping, marker-assisted selection, marker-assisted breeding. It is expedient and timely to introduce KASP genotyping technology in our country to solve a wide range of modern genetics, breeding, seed production tasks.

Main directions and results of Research on genetic diversity of maize in China and their practical use in breeding are represented.