Assessing Variation in US Soybean Seed Composition (Protein and Oil)

Abstract

Soybean [Glycine max (L.) Merr.] seed composition and yield are a function of genetics (G), environment (E), and management (M) practices, but contribution of each factor to seed composition and yield are not well understood. The goal of this synthesis-analysis was to identify the main effects of G, E, and M factors on seed composition (protein and oil concentration) and yield. The entire dataset (13,574 data points) consisted of 21 studies conducted across the United States (US) between 2002 and 2017 with varying treatments and all reporting seed yield and composition. Environment (E), defined as site-year, was the dominant factor accounting for more than 70% of the variation for both seed composition and yield. Of the crop management factors: (i) delayed planting date decreased oil concentration by 0.007 to 0.06% per delayed week (R2∼0.70) and a 0.01 to 0.04 Mg ha-1 decline in seed yield per week, mainly in northern latitudes (40–45 N); (ii) crop rotation (corn-soybean) resulted in an overall positive impact for both seed composition and yield (1.60 Mg ha-1 positive yield difference relative to continuous soybean); and (iii) other management practices such as no-till, seed treatment, foliar nutrient application, and fungicide showed mixed results. Fertilizer N application in lower quantities (10–50 kg N ha-1) increased both oil and protein concentration, but seed yield was improved with rates above 100 kg N ha-1. At southern latitudes (30–35 N), trends of reduction in oil and increases in protein concentrations with later maturity groups (MG, from 3 to 7) was found. Continuing coordinated research is critical to advance our understanding of G × E × M interactions.

Improving Seed Quality of Soybean Suitable for Growing in Europe

“…Together with understanding the sources of variation, knowing the strength and direction of relationships among different traits is of great value for breeding programmes as it enables the enhancement of more than one trait at the same time. Although significantly negative relationship between oil and protein content was reported in most researches [61,70,81,84], in the research analysing variations from 21 studies conducted over 15 years (2002-2017), Assefa et al [142] concluded that, when pooling data across all studies, there was no significant relationship between oil and protein content, but a tendency for a negative relationship was observed when plotting data separately for each of the studies evaluated in the database. Furthermore, oil content increased slowly with yield increase suggesting a positive relationship, but when relationships were investigated by study, 63% of studies supported a positive relationship, and the other 37% displayed a slightly negative relationship between seed yield and oil content [142].…”

“…Although significantly negative relationship between oil and protein content was reported in most researches [61,70,81,84], in the research analysing variations from 21 studies conducted over 15 years (2002-2017), Assefa et al [142] concluded that, when pooling data across all studies, there was no significant relationship between oil and protein content, but a tendency for a negative relationship was observed when plotting data separately for each of the studies evaluated in the database. Furthermore, oil content increased slowly with yield increase suggesting a positive relationship, but when relationships were investigated by study, 63% of studies supported a positive relationship, and the other 37% displayed a slightly negative relationship between seed yield and oil content [142]. Wilcox and Shibles [84] reported that oil increased by 1.9 g kg −1 for every 100 kg ha −1 increase in seed yield, whereas protein decreased by 15.6 g kg −1 for each 10 g kg −1 increase in oil, which is in accordance with determined significant positive correlation between oil content and yield and significant negative correlation between oil and protein contents.…”

“…Water stress negatively impacts oil content [141], but irrigation at the beginning of pod formation and during seed filling has resulted in oil content decline [51][52][53]. Some other crop management factors (no-till, seed treatments, foliar N, fungicide and insecticide applications and rotation) had an overall positive effect on oil content because they were improving crop growing conditions through conserving or supplying water and nutrients or improving soil physical and chemical properties and protecting the crop from diseases [142]. On the other hand, a decline in oil content with increased N application [141] and lack of response [143] were reported as well.…”

“…While monocropping negatively affected soybean oil composition in comparison to crop rotation with maize [144], early planting benefited oil [145][146][147]. Furthermore, Assefa et al [142] reported that planting date had larger impacts at northern latitudes (40-45 N) than southern latitudes (30-35 N). Although the influence of M for oil content was found to be significant [144][145][146][147], in a comprehensive analysis of G, M and E factors influencing soybean yield quantity and quality across the US Corn Belt, Assefa et al [142] concluded that E is a dominant factor for the significant variability in seed composition and yield.…”

“…Furthermore, Assefa et al [142] reported that planting date had larger impacts at northern latitudes (40-45 N) than southern latitudes (30-35 N). Although the influence of M for oil content was found to be significant [144][145][146][147], in a comprehensive analysis of G, M and E factors influencing soybean yield quantity and quality across the US Corn Belt, Assefa et al [142] concluded that E is a dominant factor for the significant variability in seed composition and yield. According to Josipović et al [66] and Popović et al [71], the amount of oil in soybean seed was significantly higher in years with less precipitation and higher air temperatures at the time of pod formation and dry matter accumulation.…”