Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/22/2013
Publication Date: 2/22/2013
Citation: Scandiani, M.M., Luque, A., O Donnell, K., Aoki, T., Spampinato, C., Cervigni, G. 2013. Metabolomic studies for the interaction Glycine max- Fusarium tucumaniae. Meeting Abstract. Interpretive Summary:
Technical Abstract: Sudden-death syndrome (SDS) of soybean can be caused in Argentina by 4 different Fusarium species: F. brasiliense, F. crassistipitatum, F. tucumaniae and F. virguliforme. Fusarium tucumaniae and F. virguliforme are the primary etiological agents of soybean SDS in Argentina and United States, respectively. The resistance mechanism to these pathogens in soybean is complex. Metabolomic technology was explored to phenotype resistance to F. tucumaniae. Two soybean cultivars (CV) with contrasting levels of resistance to SDS were inoculated with an isolate of F. tucumaniae grown in sorghum grain, using the layer method. Uninoculated controls were included for both genotypes. Plants were grown for 7, 10, 14 and 25 days. Four independent biological replicates were harvested at indicated times. Foliar disease, root rot incidence and severity, shoot height, shoot and root weights were rated at each time. Areas under disease severity progress curves were also calculated 25 days after inoculation (DAI). All data were subjected to statistical analysis. Means were compared by least significant differences (p<0.05). The resistant cultivar showed lower foliar disease and root rot incidence and severity, higher plant height, and root and shoot weights, than the susceptible cultivar. Uninoculated controls remained healthy. Experiments were extended to root metabolite profiling by gas chromatography mass spectrometry (GC-MS). Metabolite levels were normalized to the ribitol internal standard. Compounds were putatively identified by comparison of their retention index and mass spectrum with those present in the commercial mass spectra library NIST. Data from two biological replicates from tolerant and susceptible CVs obtained at 7, 10, 14 and 25 DAI were evaluated by principal components (PC) and principal coordinates analysis (ACoP). Analyses were either performed for individuals or pools. Results obtained allow us to identify and monitor the relative levels of 30 metabolites, including amino acids, organic acids, soluble sugars, secondary metabolites, inorganic and nitrogen compounds. These metabolites were more abundant at 7 and 10 DAI. The first two PCs (PC1 and PC2) explained 76.97 %, 84.88% and 79.11% of the variance of the susceptible, tolerant and pooled CV profiles, respectively. As these values are lower than expected (> 90%), the first four PCs had to be considered. In the susceptible CV, inorganic phosphate and sucrose showed the highest weight in PC1 and PC2, respectively. However, in the tolerant CV, inositol and sucrose were the most important variables in PC1 and malonic acid, citric acid, inorganic phosphate and myoinositol heavily contributed to PC2. When these data were pooled analyzed, inorganic phosphate and sucrose were associated with PC2 but no variables could be identified in PC1. In accordance to PC analysis, the first two ACoP factors (F1 and F2) explained the 63.90%, 67% and 43.34% of the variance of the susceptible, tolerant and pooled CV profiles, respectively. As indicated before, these percentages are lower than expected. Four DAI metabolic profiles could be clearly separated in the tolerant CV, but 7 and 10 DAI remained close together in the susceptible CV and in the pool analyses. To date, our results indicate a strong plant-pathogen interaction between 7 and 10 DAI which increases sugar, aminoacid and organic and inorganic acid levels.