Abstract
Soybean is an important high-value crop but susceptible to soil-borne diseases. A field trial was conducted in Kazakhstan to evaluate the effects of soybean cultivars and Fusarium root rot severity on soybean crop physiology, chlorophyll fractions and amino acids profile. The highest yield was achieved in 2018 (up to 4 t ha-1) for K-9648 cultivar. The greatest root rot severity (90%) and the lowest plant high (20.8 cm), number of beans per plant (54) were determined in 2020 and were related with the highest precipitations. Moreover, leaf position was crucial in determination of chlorophyll fractions, among which the highest values were achieved in 4rd leaf. Average concentration of non-essential, essential, aromatic and aliphatic amino acids were correlated with root rot development at flowering (r = 0.73) and maturing stage (r = 0.54), root rot severity (r = 0.64) and precipitations (r = 0.86). Thus, amino acids play the crucial role in defense proteins biosynthesis against biotic stress factors. Interestingly, despite Fusarium root rot occurrence, there were not determined mycotoxins in seeds, which indicate that they are not distributed to other organs from the place of their biosynthesis. This study indicated that among twelve soybean cultivars, Tanais and Isidor cultivars are at least susceptible to Fusarium root rot despite heavier rainfalls in 2020 and in this regard could be implemented to agriculture in the agro climatic conditions of Kazakhstan. However, in aspect of yield and desired amino acids profile, K-9648 cultivar was the most productive in 2018-2020.