Morphological Features of Plants and Yield of Sunflower Hybrids Cultivated in the Northern Part of the Forest-Steppe of Ukraine

In Ukraine, a sunflower is the main oil crop from which more than 90% of vegetable fats are produced. An increase in production is due to the expansion of cultivation area, which necessitates research on sunflower hybrids adaptability in the northern regions of Ukraine, where in recent decades, there has been a significant change of weather conditions and which may be favorable for its cultivation. The research was carried out in the Northern part of the Forest-Steppe of Ukraine on light loam chernozems. Reaction to growing conditions of four hybrids was studied by establishing the stability and plasticity of hybrids in terms of yield formation due to changes in morphological characteristics of plants. Yield potential realization is high enough, which is provided by sufficient amounts of positive, active, effective temperatures and precipitation. Calculation of the coefficients of plasticity and stability allows identifying stable sunflower hybrids, hybrids with a high level of plasticity, and recommending them to production. The yield of early-maturing hybrid Ukrainskyi F1 increases rectilinearly with plant density increasing (r = 0.977 - 0.998), while hybrids P63LL06 (r = 0.651 - 0.882);NK Ferti (r = 0.589 - 0.846), and NK Brio (r = 0.689 - 0.804) form a higher yield at standing densities up to 60 thousand plants per hectare, and with further thickening, the yield decreases. With the thickening of sowings, the height of all hybrids plants increases (r = 0.97 - 0.99), and there is a decrease in the number of seeds per anthode, and the weight of 1000 seeds. Sunflower hybrids can be divided into the groups according to the peculiarities of yield formation due to morphological features: 1) yield increases only due to sowings’ thickening— Ukrainskyi F1;2) combined efficiency-increasing sowings’ density to 60 thousand plants/ha and generative organs formation—NCKBrio;3) hybrids of intermediate type—NK Ferti and P63LL06.