Critical period for yield determination across grain crops.

Studies across different crops demonstrated that grain or seed number per unit area (GN m-2) is the dominant yield component. Although grains or seeds derive from floret or flower production and survival, the timing of the critical period for GN m-2 determination is known to vary noticeably, from mainly pre-flowering to strongly post-flowering, across major grain crops. Here, we demonstrate that discrepancy between crops in the timing of their critical period is related to the flowering phase duration and the proportion of the whole cycle allocated to pre-flowering development. Changing the perspective, positioning the critical period at the end of the phase when grain abortion occurs instead of flowering, results in the critical period virtually coinciding among contrasting grain crops.

Partial and total defoliation during the filling period affected grain industrial and nutraceutical quality in soybean.

BACKGROUND: Little is known about soybean grain chemical composition response to defoliation. The objectives of our study were: (i) to quantify the impact of different levels and timing of defoliation during the filling period on soybean grain yield and grain chemical content and composition, including protein, oil, fatty acids, and isoflavones; and (ii) to establish associations between them and the level and timing of defoliation. RESULTS: Yield and grain chemical components were reduced by defoliation treatments, these effects being more pronounced as defoliation increased. Mild defoliation (33%) caused small or non-significant changes in yield, its components, protein, oil, and isoflavone contents and concentrations. However, it affected oil composition, increasing the degree of unsaturation, which became more accentuated as defoliation increased. Moderate defoliation (66%) produced similar relative reductions in protein and oil contents, with small effects in isoflavone content, resulting in a generally greater isoflavone concentration in defatted flour and a greater isoflavone/protein ratio in grain. Total defoliation (100%) produced greater relative reductions in oil and isoflavone contents than in protein content. These resulted in higher protein/oil ratio and protein concentration and lower isoflavone/protein ratio and isoflavone concentration. Analyzed variables were associated with cumulative solar radiation during grain filling; indeed, this parameter successfully captured the effects of defoliation intensity and timing. CONCLUSION: By exploring different levels and timings of defoliation during the filling period, our study provides novel and important information regarding the impact of light interception decreases on grain chemical components, with special emphasis on nutraceuticals. © 2022 Society of Chemical Industry.

Benchmarking Nutraceutical Soybean Composition Relative to Protein and Oil.

The aim of this study was to explore relationships between protein, oil, and seed weight with seed nutraceutical composition, focused on total isoflavone (TI) and total tocopherol (TT) contents across genotypic and environmental combinations in soybean. We conducted a synthesis-analysis of peer-reviewed published field studies reporting TI, TT, protein, oil, and seed weight (n = 1,908). The main outcomes from this synthesis-analysis were: (i) relationship of TI-to-protein concentration was positive, though for the upper boundary, TI decreases with increases in protein; (ii) relationship of TT-to-oil concentration was positive, but inconsistent when oil was expressed in mg per seed; and (iii) as seed weight increased, TI accumulation was less than proportional relative to protein concentration and TT decreased more proportional relative to oil concentration. Association between nutraceuticals and protein, oil, and seed weight for soybean reported in the present study can be used as a foundational knowledge for soybean breeding programs interested on predicting and selecting enhanced meal isoflavone and/or oil tocopherol contents.

Leaf structure and ultrastructure changes induced by heat stress and drought during seed filling in field-grown soybean and their relationship with grain yield.

Studies focusing on terminal drought combined with heat impacts on plants of agronomic value remain scarce, and even less under field conditions. The objective of this study was to investigate leaf structural and ultrastructural changes induced by heat stress (HS) and drought stress (DS) during seed filling and their relationship with physiological variables and yield determination. Two soybean cultivars were grown in field conditions. During seed filling four treatments were applied, including a control (without manipulation, at ambient temperature and field capacity), HS (episodes exceeding 32°C for 6 h d-1) during 21-d, DS (20% of field capacity soil water content) during 35-d, and HS×DS. Drought principally reduced leaf area, whereas heat decreased leaf thickness, possible as acclimation strategies, but also irreversible reducing CO2 assimilation sites. Both stresses damaged the outer and inner membranes of chloroplasts, causing swollen chloroplasts and accumulation of plastoglobules, loss of chlorophyll content, and negatively affecting chlorophyll fluorescence. Thus, the performance and integrity of the photosynthetic machinery were reduced. Through a morpho-functional perspective and a holistic multiscale approach, our results provide evidence of photosynthesis impairment and yield drops under stressful conditions which were associated with structural and ultrastructural (particularly at the level of chloroplasts) modifications of leaves.

Leaf photosynthesis and senescence in heated and droughted field-grown soybean with contrasting seed protein concentration.

Soybean plants under heat and drought generate a multiplicity of responses in photosynthesis and senescence, impairing growth, yield, and seed quality. The goal of this study was to analyze and quantify independent and combined effects of heat and drought during seed filling on photosynthesis and senescence, and its subsequent effects on the filling duration in soybean genotypes contrasting on seed protein. Two field experiments were conducted using high and low seed protein genotypes. During seed filling plants were exposed to four treatments: control (ambient temperature and soil water content near field capacity), heat stress (HS, episodes above 32 °C 6 h d-1) during 15-d, drought stress (DS, soil water content ≤ 25% of field capacity) during the entire seed filling, and HS × DS. We found non-genotypic variation in leaf photosynthesis in both experiments. Irrigated HS, did no alter photosynthesis and senescence. Drought, regardless of heat, reduced photosynthesis, carbohydrate production and affected membranes integrity, leading to premature leaf senescence and shortening the filling duration. The magnitude of responses was similar between drought alone and stresses combined, indicating a dominant role of drought over heat. The seed filling duration was not shorter in high protein compared to low protein genotype, nor was senescence pattern altered across treatments. These results indicated that the higher seed protein content exhibited by some genotypes are not necessarily associated with an earlier onset of senescence and shortening of the filling period as suggested by previous studies analyzing genotypes differing in protein concentration.

Efecto de edulcorantes no calóricos en la aceptabilidad sensorial de un producto horneado / Effect of non-caloric sweeteners in sensory acceptability of a baked product

Samples of cakes (baked biscuit-type products) made with sugar (control) and samples prepared with non-caloric sweeteners (stevia, saccharin and sucralose) were developed and acceptability evaluated using a 5-point hedonic scale test for color, aroma and flavor. The color and aroma results indicated that the cakes made with sugar have significantly larger acceptability than cakes made with non-caloric sweeteners (p< 0.05). In assessing the acceptability of taste there are significant differences between all samples of cakes, with the following descending order according to the sweetener used: sugar > stevia > sucralose > saccharin. Replacement of sugar by non-caloric sweeteners in cakes, decreased the acceptability of the products. One explanation may be because no non-enzymatic browning reactions occur such as Maillard reaction and caramelization, which generate compounds related to color, aroma and flavor of baked foods.

Se elaboraron muestras de queques (productos horneados tipo bizcocho) con azúcar (control) y con edulcorantes no calóricos (estevia, sacarina y sucralosa). Los queques se evaluaron sensorialmente mediante una prueba de aceptabilidad con una escala hedónica de 5 puntos para los parámetros de color, aroma y sabor. Los resultados de color y aroma indican que los queques elaborados con azúcar tienen una aceptabilidad significativamente mayor que los queques elaborados con los edulcorantes no calóricos (p< 0,05). En la evaluación de sabor hubo diferencias significativas entre todas las muestras de queques, con el siguiente orden decreciente según el edulcorante utilizado: azúcar > estevia > sucralosa > sacarina. El reemplazo de azúcar por edulcorantes no calóricos en los queque, disminuyó la aceptabilidad de los productos. Una explicación posible es que no se producen reacciones de pardeamiento no enzimático como reacción de Maillard y caramelización, las que generan compuestos relacionados con el color, aroma y sabor de productos horneados.

Factors Affecting Tocopherol Concentrations in Soybean Seeds.

Soybean seeds contain several health-beneficial compounds, including tocopherols, which are used by the nutraceutical and functional food industries. Soybean tocopherol concentrations are, however, highly variable. Large differences observed in tocopherol concentrations among soybean genotypes together with the relatively simple biosynthetic pathway involving few genes support the feasibility of selecting for high-tocopherol soybean. Tocopherol concentrations are also highly influenced by environmental factors and field management. Temperature during seed filling and soil moisture appear to be the main factors affecting tocopherol concentrations; other factors such as soil fertility and solar radiation also affect concentrations and composition. Field management decisions including seeding date, row spacing, irrigation, and fertilization also affect tocopherols. Knowledge of factors affecting soybean tocopherols is essential to develop management strategies that will lead to the production of seeds with consistent target concentrations that will meet the needs of the nutraceutical and functional food industries.

Chemical compounds related to nutraceutical and industrial qualities of non-transgenic soybean genotypes.

BACKGROUND: Information about the chemical profile of soybean seed is valuable for breeding programs aimed at obtaining value-added products to meet the demands of niche markets. The objective of this study was to determine seed composition of non-transgenic soybean genotypes with specialty characters in different environments of Argentina. RESULTS: Protein and oil contents ranged from 396 to 424 g kg⁻¹ and from 210 to 226 g kg⁻¹, respectively. Oleic and linolenic acid ratio, the general indicator of oil quality, varied from 2.7 to 3.8. The oil contained high levels of total tocopherols (1429-1558 mg kg⁻¹) and the meal exhibited high levels of total isoflavones (2.91-4.62 mg g⁻¹). The biplot showed that oleic, linoleic and linolenic acids, γ-, δ- and total tocopherols, genistin, malonyl daidzin and genistin, acetyl daidzin and glycitin and total isoflavones allowed the greatest discrimination among the genotypes studied. CONCLUSION: Different chemical profiles of each non-transgenic genotype analyzed were established and, therefore, their identity was defined. These results are important for breeders who intend to obtain new genotypes with improved meal and oil quality, as well as for processors and exporters, who could use them directly as raw material for soyfood processing for nutraceutical purposes.