Evaluation of sister hybrids obtained on the basis of early maturity Iodent germplasm inbred lines (FAO 180-250) as a source material for the development of new inbred lines and evaluation of this material’s main breeding qualities as well as of level of hypothetical heterosis in sister crosses and their polymorphism as an integral part of the breeding cycle.

Field method, mathematical-statistical method.

The studies investigated sister hybrids obtained by crossing of 8 precocious Iodent germplasm inbred lines, their combining ability for “grain yield” trait and determined whether they can be used as a source material for the synthesis of new homozygous inbred lines. The results of the evaluation of sister hybrids and their testcrosses on the basic economically valuable traits are presented. According to research results in 2013-2015, it was found that sister hybrids with the least variable grain yields by years of research were obtained from the crossing of DK1274 and DK237 inbred lines. The calculations of the correlation coefficients between hypothetical heterosis and genetic distances revealed no significant correlation between them (r=0.118-0.359) as well as between the yield of sister hybrids and genetic distances (r=0.167-0.351). It was found that the least variable indicators of grain yield for the years of research were noted in sister hybrids obtained on the basis of source inbred lines with the most stable manifestation of this indicator (r=0.714). Sister hybrids were noted, which had effects of general combining ability at class 2, regardless of study conditions (DK216 × DK213, DK237 × DK1274, DK714/195 × DK216), indicating the stability of genotype response to growing conditions.

The evaluation of 8 precocious constant Iodent germplasm inbred lines on breeding traits revealed the best of them (DK555 and DK1274) in combining ability compared to the DK744 control inbred line. Significant influence of the conditions of research years on all the traits studied was noted. The study of sister hybrids has revealed forms with a significant manifestation of hypothetical heterosis. It was the highest on average in crosses of inbred lines DK234 (137.0%), DK714/195 (122.7%) and DK216 (101.1%), and the smallest in hybrids with inbred lines DK555 (58.5%), DK1274 (65.8%) and DK744 (75.0%). Sister combinations with DK1274 and DK237 inbred lines were characterized by the highest yield stability over the years of study. In determining genetic distances, the most genetically similar inbred lines DK744 (0.136) and DK234 (0.197) to inbred line 207 (P165), which is the classic representative of the Iodent germplasm, are noted.