Asian Soybean Rust (ASR), caused by the biotrophic fungus Phakopsora pachyrhizi, is a devastating disease with an estimated crop yield loss of up to 90%. Yet, there is a nerf of information on the metabolic response of soybean plants to the pathogen Untargeted metabolomics and Global natural products Social Molecular networking platform approach was used to explore soybean metabolome modulation to P. pachyrhizi infection. Soybean plants susceptible to ASR was inoculated with P. pachyrhizi spore suspension and non-inoculated plants were used as controls. Leaves from both groups were collected 14 days post-inoculation and extracted using different extractor solvent mixtures. The extracts were analyzed on an ultra-high performance liquid chromatography system coupled to high-definition electrospray ionization-mass spectrometry. There was a significant production of defense secondary metabolites (phenylpropanoids, terpenoids and flavonoids) when P. pachyrhizi infected soybean plants, such as putatively identified liquiritigenin, coumestrol, formononetin, pisatin, medicarpin, biochanin A, glyoceollidin i, glyoceollidin ii, glyoceollin i, glyoceolidin ii, glyoceolidin III, glyoceolidin IV, glyoceolidin VI. Primary metabolites (amino acids, peptides and lipids) also were putatively identified. This is the first report using untargeted metabolomics and GNPS-Molecular Networking approach to explore ASR in soybean plants. Our data provide insights into the potential role of some metabolites in the plant resistance to ASR, which could result in the development of resistant genotypes of soybean to P. pachyrhizi, and effective and specific products against the pathogen. The soybean (Glycine max (L.) Merrill) is prominent among crops due to its agro-economic and nutritional value, used mainly as a source of proteins and oils for human consumption, in animal feeds and for biofuel production 1,2. However, estimates indicate a necessity to double global agricultural output by 2050 to feed a rising population, hence soybean productivity needs to be increased by 2.4% per annum 3. Yet, soybean diseases were estimated to reduce crop yield by 11% in the United States 4 and 50% or greater in the southeastern United States 5. The Asian Soybean Rust (ASR) was registered for the first time in Brazil during the 2001/2002 harvest 6. Recently, Brazilian soybean farmers spent US$ 2.16 billion with fungicides during the 2016/2017 harvest, and 96% of the sum was used for ASR control. Another US$ 1.62 billion was invested on insecticides, totaling US$ 3.78 billion. This amount represented 12.4% of the production costs for the harvest 7. Despite increasing costs, disease management practices are needed as yield losses of up to 90% have already been reported when control measures were absent 4 .

Phakopsora pachyrhizi is a biotrophic fungus, causer of the disease Asian Soybean Rust, a severe crop disease of soybean and one that demands greater investment from producers. Thus, research efforts to control this disease are still needed. We investigated the expression of metabolites in soybean plants presenting a resistant genotype inoculated with P. pachyrhizi through the untargeted metabolomics approach. The analysis was performed in control and inoculated plants with P. pachyrhizi using UHPLC-MS/MS. Principal component analysis (PCA) and the partial least squares discriminant analysis (PLS-DA), was applied to the data analysis. PCA and PLS-DA resulted in a clear separation and classification of groups between control and inoculated plants. The metabolites were putative classified and identified using the Global Natural Products Social Molecular Networking platform in flavonoids, isoflavonoids, lipids, fatty acyls, terpenes, and carboxylic acids. Flavonoids and isoflavonoids were up-regulation, while terpenes were down-regulated in response to the soybean–P. pachyrhizi interaction. Our data provide insights into the potential role of some metabolites as flavonoids and isoflavonoids in the plant resistance to ASR. This information could result in the development of resistant genotypes of soybean to P. pachyrhizi, and effective and specific products against the pathogen.

The objective of this work was to quantify biomethane from anaerobic degradation of microalgae biomass harvested from a field-scale tank reactor simulating phycoremediation of swine wastewater. The effects of nutrients starvation on microalgae chemical cellular composition changes and its influence on biomethane generation potential were also addressed. Microalgae polyculture was dominated by uncultured Scenedesmus clone BF 063 which showed a carbohydrate, protein and lipid content of 27.6 ± 3.3, 57.6 ± 0.1 and 3.9 ± 0.6%, respectively. After 25 days exposed to N-and P-free medium, microalgae biomass composition showed 54.6 ± 2.6, 24.1 ± 2.4 and 16.9 ± 0.8% of carbohydrate, protein and lipid, respectively. Volatile solids concentration in the biomass harvested from N-and P-rich medium was lower [67 ± 1.7 g VS (kg biomass) À1 ] than biomass harvested from nutrient depleted medium [204.1 ± 3.1 g VS (kg biomass) À1 ]. Consequently, much higher biomethane production was obtained i.e., 103.5 L N CH 4 (kg biomass) À1 vs 44 L N CH 4 (kg biomass) À1. The results suggest that biomethane production in digesters could be improved by integrating microalgae biomass harvested from algae-based swine wastewater digestate treatment.

Metabolomics is an omics technology that is extremely valuable to analyze all small-molecule metabolites in organisms. Recent advances in analytical instrumentation, such as mass spectrometry combined with data processing tools, chemometrics, and spectral data libraries, allow plant metabolomics studies to play a fundamental role in the agriculture field and food security. Few studies are found in the literature using the metabolomics approach in soybean plants on biotic stress. In this review, we provide a new perspective highlighting the potential of metabolomics-based mass spectrometry for soybean in response to biotic stress. Furthermore, we highlight the response and adaptation mechanisms of soybean on biotic stress about primary and secondary metabolism. Consequently, we provide subsidies for further studies of the resistance and improvement of the crop.