The features of stem length generation of breeding numbers of winter wheat  T. aestivum of L. of different origin as contrasted to hydrothermal indices in the years of research are presented.  Semidwarf breeding numbers 17 CS, 26 CS and medium-grown standard variety Pearl of forest-steppe had a resistance to lodging at the level of 9 marks. It is found the effect of internodes of different location order on forming of wheat stem length. It is investigated the correlation of length of internodes according to their location. Certain coefficients of stem length and internodes variations are determined.

Wheat – one of the main food grain crops in Ukraine. Researches of the leading scientific establishments give evidence that the important factor of growth and stabilizing of crop productivity is creation and introduction of varieties with high potential of productivity and adaptation to the unfavorable patterns of environment. In the conditions of intensive production only plant varieties patient to lodging are able to use effectively the raised dosage of mineral fertilizers.

Wheat stem, or straw, is an organ discharging  important physiological functions of photosynthesis and transporting metabolites in ontogenesis. The morphology and anatomy features of stem determine lodging resistance of plants and their ability to realize productive potential.

Nodes and internodes of wheat are formed on І and ІІ stages of organgenesis yet to the beginning of stem growth, which is accepted to determine from the moment of lengthening of the first surface internode, i.e. phases of output in a tube (IV stage of organogenesis), when it is appeared the first stem node at the distance of 2-5 cm from the soil surface on the main sprout. This phase comes in 25-35 days after spring vegetation stimulation and lasts for 25-30 days. Growth of wheat stem shows up mainly the considerable lengthening of internodes and to a lesser extent their thickening. Length of straw, growth of which lasts to the beginning of beetle forming (ІХ stage of organgenesis), is controlled genetically and at the same time considerably depends on environment patterns.

The purpose of research was a comparative evaluation of semidwarf  and medium-grown  breeding  numbers of soft winter wheat, obtained at Bila Tserkva experimentally-plant-breeding station in 2011-2013 by crossing of varieties belonging to different ecological groups, according to the length of main stem and internodes, and also determination of plant reaction limit of changing growth environment.

In 2011  semidwarf breeding numbers had a length of stem within the limits of 57,2-75,2 cm. It was examined that only numbers 26 CS and 17 CS had the highest index of lodging resistance– 9,0 marks.

In the group of medium-grown  genotypes the index of lodging resistance varied from 5,0 marks (7 CS) to 8,6 marks (8 CS), with stem length – 85,6-98,1 cm. Due to internodes of different order of location stem length generation differed from semidwarf breeding numbers.

The analysis of stem length in 2012 testifies that medium-grown  breeding numbers had, on the average, an index at the level of 2011 year. Stem length of semidwarfs, on the average, was on 5,2 cm greater. Under stem length criterion plant-breeding numbers 17 CS and 22 CS exceeded an index of 2011 year on 13,1 and 9,4 cm accordingly. Plant-breeding numbers and standard varieties had lodging resistance with  about 9,0 marks.

In 2013 stem length of semidwarf breeding numbers was formed in the most unfavorable conditions and was within limits of 49,4-56,0 cm, that was considerably below indices of the previous years. The stem length of medium-grown  genotypes was 51,1-73,8 cm and according to these figures they belonged  to semidwarf numbers.

Plant-breeding numbers 26 CS, 17 CS and medium-grown standard variety Pearl of forest-steppe had resistance to lodging at the level of 9,0 marks during the years of research and we recommended them to be used as parent material  for creating varieties of universal type.

Key words: winter wheat, plant-breeding numbers, hydrothermal coefficient, stem length, internode.