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.

Purpose. Revealing of adaptive properties of plant varieties of red beet Bordeaux Kharkivskyi and Aktion based on the study of plant growth regulators for marketable production in the Steppe zone of Ukraine. Methods. Field, laboratory ones, variance analysis. Results. The influence of plant growth regulators (Lignogumat, Betastimulin) on earliness and productivity of such red beet varieties as Bordeaux Kharkivskyi and Aktion was established. Conclusions. Plant growth regulators (Betastimulin, Lignogumat) stimulated seed sprouting of red beet Bordeaux Kharkivskyi and Aktion varieties, activated vegetative plant growth increa­sing marketable yield. Application of Betastimulin (0.2%) for red beet Kharkivskyi Bordeaux and Aktion varieties provides the highest number of marketable beetroots, thus forming marketable yield of 44.7 and 54.9 t/ha respectively with the average beetroot weight of 328–519 g.

Analysis of the existing methods for earliness group determination of maize varieties and hybrids according to the FAO indices was conducted. Influence of the abiotic factors on earliness of 16 standard maize hybrids in all agroclimatic zones of Ukraine at nine State Canters for Plant Variety Examination and State Variety Testing Stations during 1999-2006 was analyzed. On the base of the research results, a new method of earliness group determination for varieties (hybrids) of maize without comparison with the standard hybrids has been developed.