Dynamics of tocopherol concentrations accumulation in soybean exposed to brief episodes of heat and drought stress during grain filling

VEAS R.E.A.; ERGO V.V.; ASÍS R.; LASCANO H.R. ; CARRERA C.S.

Rosario

Congreso; XXXIV Reunión de la Sociedad Argentina de Fisiología Vegetal; 2023

Sociedad Argentina de Fisiología Vegetal

Soybean oil contains tocopherols, antioxidant compounds that have nutraceutical value for humans. Tocopherol isoforms are alpha, beta, gamma, and delta tocopherol (α-, β-, γ-, and δ-toc, respectively). The objective was to determine tocopherol concentrations of soybean exposed to heat stress (HS) and drought stress (DS) during grain filling period (GFP). We hypothesized that HS and DS modified tocopherols accumulation pattern during GFP (R5-R7) negatively impacting on total tocopherols (T-toc) at harvest. We conducted a greenhouse experiment using a non-transgenic soybean genotype. Four treatments were evaluated: control, plants under irrigation, at 80% of soil field capacity (FC); HS, plants under irrigation exposed to temperatures >32°C for 6h around noon; DS, plants maintained at 40%FC, and plants under HS×DS interaction. At stages R5, R5.5, R6, R6.5 and R8, previously marked pods were collected for tocopherols determination. The T-toc resulted from summing α-, β-, γ-, and δ-toc. At R5.5, non-significant changes (p>0.05) were observed for α-toc, β-toc and T-toc, while γ-toc decreased 8% on HS and increased on average 17% under DS and HS×DS. δ-toc decreased on average 15% among stress treatments. At R6, α-toc increased markedly under three stresses, reaching 181% on HS×DS. In contrast, δ-toc decreased, although to a lesser extent, by 28% on average. β-toc increased by 33% under HS and 59% under DS; whereas γ-toc decreased 16% on average under HS. At R6.5 a similar trend to R6 was observed. At R8, α-toc increased 24% under HS and 64% under DS, β-toc increased 50% under DS; whereas δ-toc decreased under both stresses (15 and 8%, respectively), with non-significant changes of γ-toc and T-toc by any stress. We conclude that, although the tocopherol isoforms varied during GFP, this did not negatively impact on T-toc at harvest. Furthermore, α-toc stood out as the most sensitive isoform, always increasing under stress conditions.