Influence of external conditions on the manifestation of the average number of tubers in the bush among interspecifics hybrids of potatoes, their backcrosses

The ability to form a large number of tubers in the nest positively affects the productivity of hybrids and potato varieties. However, the expression of the trait is subject to a significant influence of external conditions, depending on the rate of response of the genotype. Studies on the assessment of the varying complexity of interspecific hybrids, their backcrosses in the ability to tie tubers were carried out during 2015‒2017 in three places: the experimental field of the Sumy National Agrarian University (hereinafter SNAU), the Ustimov Experimental Plant of the V. Y. Yuryev Institute of Plant Production of the NAAS of Ukraine (UES ), as well as the Institute of Potato Production of the NAAS of Ukraine (IR). The source material used 26 complex interspecific hybrids, their backcrosses. Varieties standards was Yavir and Grouse. The technique is generally accepted in the study with potatoes. The locations and years of the experiment varied significantly in meteorological conditions. SNAU alone had more rain in 2016 than in many years. In the UES, this applied to 2015 and 2016, and in the IR all the years there was a significant deficit in the supply of moisture with rains. Under the conditions of SNAU, only three decades from 12 in 2015, the air temperature was below the long-term average. In subsequent years there were five. In UES, this, respectively, amounted to 5, 7 and 7 decades. In IK, in all months, the air temperature was above the long-term average; in May 2015 and August 2015 and 2017, the difference exceeded 50 °C. The high potential of the studied samples was determined by the ability to tie tubers. In some hybrids, under optimal conditions, their average number in the nest exceeded 20 pcs. A particularly positive effect on the formation of tubers was revealed in 2016 in the IR, when some of them with the maximum manifestation of the trait amounted to 32.1 %. To a lesser extent, the foregoing related to a part of the material with the number of tubers in the nest of 10 pieces and more ‒ 8.4 %. In all places throughout all years hybrids with the best tuber-forming ability were distinguished than the variety-standard Teterev. In general, some of these hybrids amounted to 0.4‒7.7 %. The distribution data of the manifestation of the trait among hybrids depending on the place and years of testing indicate that in 2015 and 2016 with a tuber/nest of 8.1–10.0 tubers/nest, and 6.1–8.0 in the latter, the modal class in SNAU. Very unfavorable conditions for tying tubers were identified in 2016 under the conditions of UES. More than half of the test material is assigned to class 4 tuber/nest and less. In the other two years, the modal class was 6.1‒8.0 tuber/nest. In all years, under conditions of infrared hybrids there was no hybrids with a minimum value of the indicator, and the modal classes were, respectively, 8.1‒10.0; more than 12.0 and 6.1‒8, as well as 8.1‒10.0.