Effect of Shade on Seed Protein, Oil, Fatty Acids, and Minerals in Soybean lines Varying in Seed Germinability in the Early Soybean Production System

The cause of poor seed quality (germination) of soybean produced in the Early Soybean Production System in the midsouth U.S.A. is still not completely understood. Temperature, solar radiation, and soybean genotype may all be important factors involved. The objective of this research was to evaluate seed composition, mineral level, and nitrogen assimilation in high and low germinability soybean plant introductions in a full-sunlight (unshaded) and a low-light intensity (shaded) environments. Shade netting was employed in field plots that reduced light intensity by about 50% and air temperature by about 10?F/6?C (10%). A two-year field experiment was conducted on soybean accessions with high germinability (PI 587982A and PI 603723), low germinability (PI 80480 and PI 84976-1), and on soybean cultivars (DSR-3100 RR STS and Pella 86). Results showed that shade resulted in higher total oil, linoleic and linolenic acids, and lower protein and oleic acid. Shade also resulted in lower nitrogen assimilation, leaf chlorophyll concentration, but unshade resulted in higher total seed boron, iron, and nitrogen concentrations. Seed structural boron was positively correlated with germination and protein. Structural boron percentage was consistently higher under shade than under unshade in PI 80480, PI 84976-1, DSR-3100 RR STS, and Pella 86, but consistently higher under unshade than under shade in higher germinability lines PI 587982A and PI 603723, suggesting that different distribution mechanisms of structural boron exist between genotypes. The positive correlation between germination and structural B and between protein and structural B signify a possible role of B in seed quality traits. Our research demonstrated that light intensity, combined with temperature, can alter seed constituents. Higher germinability lines had higher germination rates and lower percentages of hardseededness, desirable traits for soybean seed.

Influence of Planting Date on Seed Protein, Oil, Sugars, Minerals, and Nitrogen Metabolism in Soybean under Irrigated and Non-Irrigated Environments

Information on the effect of planting date and irrigation on soybean [Glycine max (L.) Merr.] seed composition in the Early Soybean Production System (ESPS) is deficient, and what is available is inconclusive. The objective of this research was to investigate the effects of planting date on seed protein, oil, fatty acids, sugars, and minerals in soybean grown under irrigated (I) and non-irrigated (NI) conditions. A 2-yr field experiment was conducted in Stoneville, MS in 2007 and 2008. Soybean was planted during second week of April (early planting) and second week of May (late planting) each year. Results showed that under irrigated condition, early planting increased seed oil (up to 16% increase) and oleic acid (up to 22.8% increase), but decreased protein (up to 6.6% decrease), linoleic (up to 10.9% decrease) and linolenic acids (up to 27.7% decrease) compared to late planting. Under I conditions, late planting resulted in higher sucrose and raffinose and lower stachyose compared with early planting. Under NI conditions, seed of early planting had higher protein (up to 4% increase) and oleic acid (up to 25% increase) and lower oil (up to10.8% decrease) and linolenic acids (up to 13% decrease) than those of late planting. Under NI, stachyose concentration was higher than sucrose or raffinose, especially in early planting. Under I, early planting resulted in lower leaf and seed B, Fe, and P concentrations compared with those of late planting. Under NI, however, early planting resulted in higher accumulation of leaf B and P, but lower seed B and P compared with those of late planting. This research demonstrated that both irrigation and planting date have a significant influence on seed protein, oil, unsaturated fatty acids, and sugars. Our results suggest that seed of late planting accumulate more B, P, and Fe than those of early planting, and this could be a beneficial gain. Limited translocation of nutrients from leaves to seed under NI is undesirable. Soybean producers may use this information to maintain yield and seed quality, and soybean breeders to select for seed quality traits and mineral translocation efficiency in stress environments.

Soybean seed protein, oil, and fatty acids are altered by S and S + N fertilizers under irrigated or non-irrigated environments

Information on the effect of sulfur (S) or sulfur+nitrogen (S + N) on soybean seed composition is scarce. Thus, the objective of this study was to investigate the effects of S, and S + N fertilizers on soybean [(Glycine max (L.) Merr.)] seed composition in the Early Soybean Production System (ESPS) under irrigated (I) and nonirrigated (NI) environments. Two separate field experiments were conducted from 2005 to 2007. One experiment was irrigated, and the second experiment was nonirrigated. Under I condition, S at a rate of 44.8 kg/ha alone or with N at 112 kg/ha resulted in a consistent increase in seed protein and oleic acid concentrations, and a decrease in oil and linolenic acid concentrations compared with the control (C). For example, in 2006 and compared with the C, application of S + N increased the percentage up to 11.4% and 48.5% for protein and oleic acid, respectively. However, oil concentration decreased by 3%. Protein and oleic acid increase were accompanied by a higher percentage of leaf and seed N and S. Under NI conditions, seed protein and oleic acid concentrations were significantly higher in C than in any S or S + N treatments, but the oil and linolenic acid concentrations were significantly lower. The results indicate that specific rate of S alone or S + N combined can alter seed composition under irrigated or nonirrigated conditions. This knowledge may help plant breeders to develop and release cultivars to suit specific target locations to grow new value-added soybeans or select for specific seed composition traits under specific environmental stress factors such as drought.

Soybean seed protein, oil, fatty acids, N, and S partitioning as affected by node position and cultivar differences

The mechanisms controlling the partitioning of seed composition constituents along the main stem in soybean are still controversial. Therefore, the objective of this study was to investigate seed protein, oil, and fatty acids partitioning in soybean cultivars along the main stem. The cultivars were DT97-4290, maturity group (MG) IV;Stressland, MG IV;Hutcheson, MG V;TracyM, MG VI. Seeds were harvested based on position on the plant (top nodes, middle nodes, and bottom nodes). At R8 (physiological maturity stage), DT97-4290, Hutcheson, and Stressland had higher percentage of protein and oleic acid and lower percentage of oil and linolenic acid in top node seed compared with bottom node seed. The increase of protein in top node compared with the bottom node across the two experiments ranged from 15.5 to 19.5%, 7.0 to 10.5%, 14.2 to 15.8%, 11.2 to 16.5%, respectively for DT97-4290, Hutcheson, Stressland, and TracyM. Except for TracyM, the increase of oleic acid in the top node ranged from 45.4 to 93%, depending on the cultivar. Conversely, the decrease in the top node seed ranged from 14.4 to 26.8% for oil and from 5.7 to 34.4% for linolenic acid, depending on the cultivar. The partitioning trend of seed composition constituents at R6 (seed - fill stage) was inconsistent. Except for Stressland, seed oleic acid was higher at R6 than at R8. The higher protein and oleic acid concentrations in the top node seed was accom- panied by higher activity of nitrate reductase activity, higher chlorophyll concentration, higher nitrogen (N) and sulfur (S) percentages in the fully expanded leaves at R5-R6 growth stage, and higher seed nitrogen (N) and sulfur (S) percentages in DT 97-4290 and Stressland. The current research suggests that the partitioning of seed protein, oil, and fatty acids in nodes along the plant depended on the position of node on the main stem, cultivar differences, seed N and S status, and tissue N and S partitioning. The higher nitrate reductase activity at the top nodes, accompanied higher protein and oleic acid, and the changes of oleic acid at R6 and R8 along the stem, were not previously reported, and need further investigation. The current knowledge is useful for soybean germplasm selection for desirable traits such protein and oleic acid, and for accurate measurements of seed composition constituents in breeding lines.