Adam L. Heuberger

Most food crops are susceptible to necrotrophic bacteria that cause rotting and wilting diseases in fleshy organs and foods. All varieties of cultivated potato (Solanum tuberosumL.) are susceptible to diseases caused byPectobacteriumspecies, but resistance has been demonstrated in wild potato relatives includingS. chacoense. Previous studies demonstrated that resistance is in part mediated by antivirulence activity of phytochemicals in stems and tubers. Little is known about the genetic basis of antivirulence traits, and the potential for inheritance and introgression into cultivated potato is unclear. Here, the metabolites and genetic loci associated with antivirulence traits inS. chacoensewere elucidated by screening a sequencedS. tuberosumxS. chacoenserecombinant inbred line (RIL) population for antivirulence traits of its metabolite extracts. Metabolite extracts from the RILs exhibited a quantitative distribution for two antivirulence traits that were positively correlated: quorum sensing inhibition and exo-protease inhibition, with some evidence of transgressive segregation, supporting the role of multiple loci and metabolites regulating these resistance-associated systems. Metabolomics was performed on the highly resistant and susceptible RILs that revealed 30 metabolites associated with resistance, including several alkaloids and terpenes. Specifically, several prenylated metabolites were more abundant in resistant RILs. We constructed a high-density linkage map with 795 SNPs mapped to 12 linkage groups, spanning a length of 1,507 cM and a density of 1 marker per 1.89 cM. Genetic mapping of the antivirulence and metabolite data identified five quantitative trait loci (QTLs) related to quorum sensing inhibition that explained 8-28% of the phenotypic variation and two QTLs for protease activity inhibition that explained 14-19% of the phenotypic variation. Several candidate genes including alkaloid, and secondary metabolite biosynthesis that are related to disease resistance were identified within these QTLs. Taken together, these data support that quorum sensing inhibition and exo-protease inhibition assays may serve as breeding targets to improve resistance to nectrotrophic bacterial pathogens in potato and other plants. The identified candidate genes and metabolites can be utilized in marker assisted selection and genomic selection to improve soft- rot and blackleg disease resistance.

Potato is a major staple crop, and necrotrophic bacterial pathogens such as Pectobacterium spp. are a major threat to global food security. Most lines of cultivated potato ( Solanum tuberosum) are susceptible to Pectobacterium spp., but some lines of wild potato are resistant, including Solanum chacoense M6. Despite the discovery of resistance in wild potatoes, specific resistance genes are yet to be discovered. Crude protein extract from M6 had a global effect on Pectobacterium brasiliense Pb1692 (Pb1692) virulence phenotypes. Specifically, M6 protein extracts resulted in reduced Pectobacterium exo-protease activity and motility, induced cell elongation, and affected bacterial virulence and metabolic gene expression. These effects were not observed from protein extracts of susceptible potato S. tuberosum DM1. A proteomics approach identified protease inhibitors (PIs) as candidates for S. chacoense resistance, and genomic analysis showed higher abundance and diversity of PIs in M6 than in DM1. We cloned five PIs that are unique or had high abundance in M6 compared with DM1 and purified the proteins (g18987, g28531, g39249, g40384, g6571). Four of the PIs significantly reduced bacterial protease activity, with strongest effects from g28531 and g6571. Three PIs (g18987, g28531, g6571) inhibited disease when co-inoculated with Pectobacterium pathogens into potato tubers. Two PIs (g28531, g6571) also significantly reduced Pb1692 motility and are promising as resistance genes. These results show that S. chacoense PIs contribute to bacterial disease resistance by inhibiting exo-proteases, motility, and tuber maceration and by modulating cell morphology and metabolism. [ ] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

In the brewing industry, there is value in defining sensory attributes of malt, and recent protocols have been developed that enable analysis of aroma and taste. One method, the “hot steep,” is a hot water extract that is highly reproducible and able to distinguish malt flavor. However, the chemistry of the hot steep extracts has not been fully defined, and the links between specific metabolites of the hot steep and their resulting sensory attributes remains largely unknown. Here, a study was designed to describe the metabolite chemistry of hot steep extracts, and to characterize variation in this chemistry and corresponding sensory by comparative analysis of 12 commercial pale malts. Metabolomics was performed on the 12 malt hot steep extracts using three mass spectrometry platforms to detect volatiles (HS/SPME-GC-MS) and non-volatiles (UHPLC-TOF-MS and GC-MS). The analysis detected a total of 1,026 compounds including lipids, organic acids, esters, and Maillard Reaction Products (MRPs), of which 162 compounds (15.7%) varied among the 12 hot steep extracts. Sensory of the 12 hot steep extracts was performed using an integrated Check All That Apply and quantitative analysis method for 14 traits, and the data revealed cereal, grassy, and dough aromas were the attributes that varied. The metabolomics and sensory data were integrated using OPLS analysis. The analysis revealed 64 compounds strongly associated with cereal aroma and included MRPs. A total of 23 compounds were strongly associated with grassy aroma including alkane/alkenes, benzenoids, organic acids, lipids, and fatty acid esters. Taken together, these data highlight the utility of the hot steep extract to differentiate malt for flavor and chemistry and indicate specific compounds that drive the most dominant flavors observed in this population of pale malts.

Potato (Solanum tuberosum L.) is the primary vegetable crop consumed worldwide and is largely affected by bacterial pathogens that can cause soft rot and blackleg disease. Recently, resistance to these diseases has been identified in the wild potato S. chacoense, and the mechanism of resistance is unknown. Here, it was hypothesized that S. chacoense stems or tubers have unique chemistry that confers resistance to the pathogen Pectobacterium brasiliense through bactericidal, bacteriostatic, or antivirulence activity. Stem and tuber metabolite extracts were collected from S. chacoense and tested for effects on Pectobacterium bacterial multiplication rates, and activity and expression of known exoenzymes and virulence genes using S. tuberosum extracts as a comparative control. Comparatively, the S. chacoense extracts did not affect bacterial multiplication rate; however, they did reduce pectinase, cellulase, and protease activities. The chemical extracts were profiled using a bioassay-guided fractionation, and a nontargeted metabolomics comparison of S. chacoense and S. tuberosum stems and tubers was performed. The data showed that selected alkaloids, phenolic amines, phenols, amines, and peptides are integrative chemical sources of resistance against the bacteria. [ ] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Recent research has demonstrated contributions of barley genotype to beer flavor based on the progeny of a cross between an heirloom and a more contemporary barley variety. To advance this line of research, the current study used two independent sets of barley germplasm to address the contributions of different barley genotypes to beer flavor. Pedigree, quality of malt and beer, and beer metabolomic profiles were compared within and between the two sets. Utilizing both laboratory and consumer panels, differences in sensory attributes of malt hot steeps and lager beers that are attributable to barley genotype were investigated. Genotype, in this context, is defined in the broadest sense to include experimental germplasm and released varieties. Results concur with previous studies: the two sets of barley germplasm were found to have, both within and between, distinct but subtle differences in flavor profiles of malt hot steeps and finished lager beers. Distinct metabolomic profiles, attributable to barley genotype, were detected. Further, covariation of metabolomic profiles and sensory attributes were identified using data from both sensory panels. These observations lead to the conclusion that the variable metabolites observed among the two sets of barley germplasm are a direct result of genetic differences that lead to differential chemical responses within the malting and brewing processes.

The dietary fiber gap that is present in many countries co-exists with a low intake of grain legumes (pulses) that have 2–3 times more dietary fiber than cereal grains that are commonly recommended to increase fiber intake. Given the relationships among dietary fiber, gut health and chronic disease risk, a study was undertaken in a preclinical mouse model for obesity to examine how commonly consumed pulses, i.e., chickpea, common bean, dry pea and lentil, would impact gut microbes, intestinal function, and adiposity. Pulses were fed to C57BL/6 mice at similar levels of protein and fiber. Bacterial count in the cecum was elevated 3-fold by pulse consumption. At the phylum level, a 2.2- to 5-fold increase in Bacteriodetes relative to Firmicutes was observed. For Akkermansia muciniphila, a health-beneficial bacterium, differential effects were detected among pulses ranging from no effect to a 49-fold increase. Significant differences among pulses in biomarkers of intestinal function were not observed. Pulses reduced accumulation of lipid in adipose tissue with a greater reduction in the subcutaneous versus visceral depots. Metabolomics analysis indicated that 108 metabolites were highly different among pulse types, and several compounds are hypothesized to influence the microbiome. These results support recent recommendations to increase consumption of pulse-based foods for improved health, although all pulses were not equal in their effects.

Previous research demonstrates that barley genetics can influence beer flavor. However, the chemical basis for differences in beer flavor attributed to barley is not well defined. Here, the associations between beer volatile compounds and sensory descriptors were investigated in a controlled experiment, whereby barley genotype was the main driver of variation in the system. Beer was brewed from three advanced barley breeding lines and compared to a CDC Copeland control. Sensory studies were performed via three independent panels (a consumer, brewery, and laboratory panel). The results suggest that the four beer samples have distinct flavor profiles that could be discriminated by the three sensory panels. Volatile compounds for the four beers were characterized using HS/SPME-GC-MS; quantitation and annotation were performed using a non-targeted metabolomics approach on 397 detected compounds. The O2PLS data analysis supports that alkane/alkenes, benzenoids, amides/amines, and fatty acid esters were associated with the most desirable lager traits, compared to Maillard Reaction Products that were more abundant in the beers with “non-ideal” lager traits. Taken together, these data further support the role of barley genetics in beer flavor and provide new information on the types of volatile metabolites that can vary in controlled systems.