Determination of drought resistance of soybean breeding material
Authors: Ryabukha S. S. , Chernyshenko P. V. , Bezuglу І. М. , Golokhorynska M. G. 
Published: August 2023

The purpose and objectives of the study. To determine the resistance of soybean genotypes to drought according to drought resistance indices based on the analysis of yield in years contrasting in terms of hydrometeorological conditions.
Materials and research methods. The material for determining the influence of year conditions on the level of average yield of soybeans and drought resistance were varieties and breeding numbers of the competitive variety test (CVT). Experiments were carried out in four repetitions with a plot area of 25 m2. Drought intensity (D) was determined by the formula proposed by Fischer R.A. and Maurer R. Differentiation of breeding numbers and varieties of CVT soybeans was carried out according to yield in 2016 and 2018 according to indices of drought susceptibility (DSI), drought tolerance (TOL), average yield (MP), yield stability (YSI), yield (YI), stress tolerance (STI), geometric mean yield (GMP). Processing of research results was carried out according to B.O. Dospehov [27] using STATISTICA 10 and Excel programs.
The discussion of the results. During the research period (2008–2021), the highest yield of soybeans in CVT was obtained in 2016 – 2.57 t/ha, and the lowest in 2018 – 0.50 t/ha. A comparison of soybean yield in CVT in 2016 and 2018 showed that the average yield loss due to drought was 2.07 t/ha, or 81%. At the minimum yield, losses were equal to 1.78 t/ha, or 84.8%. At the maximum – 2.19 t/ha and 75.5%, respectively. Therefore, the minimum yield difference was greater than the maximum yield difference. The level of drought intensity (D) in the dry year of 2018 was equal to 0.81.
According to yield indicators, a number of indices were calculated and analyzed, which characterize the resistance of samples to drought. The value of the drought susceptibility index (DSI) ranged from 0.87 to 1.09, with an average value of 1.00. The drought tolerance index (TOL) was 1.61–2.41 with an average value of 2.11. The average yield (MP) was in the range of 2.34–3.15 t/ha and had an average value of 2.85 t/ha. The yield stability index (YSI) value varied from 0.12 to 0.30 with an average value of 0.19. The yield index under stress conditions (YI) was 64.6–143.3%, with an average value of 98.9%. The stress yield index (YI) ranged from 64.6% to 143.3%, with an average value of 98.9%. The geometric mean (or proportional mean) yield (GMP) of the studied samples ranged from 0.92 t/ha to 1.38 t/ha, with a median value of 1.11 t/ha.
According to each index, the researched soybean samples were differentiated and drought-resistant breeding material was selected.
Conclusions. According to most indices: stress susceptibility (DSI), drought tolerance (TOL), crop stability (YSI), productivity (YI), stress tolerance (STI) and geometric mean yield (GMP) number CVT 23-18 (3836 / 76-130 selection). According to five indices: stress susceptibility (DSI), yield stability (YSI), yield (YI), stress tolerance (STI) and geometric mean yield (GMP) number CVT 16-18 (Volgohradka / Mriya) stood out. Number CVT 49-18 (Kharkivska 56 / Ilsoy) stood out according to the indicators of four indices: average yield (MR), yield (YI), stress tolerance (STI) and geometric mean yield (GMP). According to three indices, it is identified as drought-resistant number CVT 22-18 (selection №14) – according to indices of stress susceptibility (DSI), drought tolerance (TOL) and yield stability (YSI); numbers CVT 36-18 (Kharkivska zernokormova / Yug 30) and CVT 24-18 (Kharkivska 62 / Hodson) – according to indices of yield (YI), stress tolerance (STI) and geometric mean yield (GMP). Selection number CVT 28-18 (4305-04) stood out according to stress tolerance index (TOL) and average yield level (MR). Number 29-18 (Narrow-leaved / mutant 82-205) stood out according to the stress tolerance index (TOL) and the level of average yield (MR). Numbers CVT 50-18 (selection from Pasteter Schwarus) and CVT 37-18 (Success / Dream) were distinguished by indices of susceptibility to stress (DSI) and yield stability (YSI). According to the level of average yield (MR), number CVT 20-18 (Kharkivska 35 / Kyivska 27) and Podyaka variety stood out. The Roksolana variety stood out according to the stress tolerance index (TOL). Selected genotypes of soybeans with a high level of resistance to abiotic stress are recommended for use in crop breeding for high drought resistance.