Abstract
In recent years, the global need for a sustainable lifestyle and the green transition has become crucial in the fight against climate change. Agricultural production is responsible for a large part of greenhouse gas emissions, and the industry requires transformation to support a sustainable future. Intercropping is a well-known cropping system, and the use of legumes in intercropping has gained much attention in the search for sustainable agricultural solutions due to their nitrogen fixation ability. Intercropping has several benefits, such as improved soil fertility, increased grain yield and reduced pests and weeds. Crops synthesise and exude plant-specialised metabolites, such as flavonoids, in their interaction with neighbouring plants and other organisms. Flavonoids in plants are well-studied defence compounds, but little is known about the effect of intercropping on their composition and concentration. Therefore, this study aimed to explore the effect of lupin-barley intercropping on flavonoid concentration in roots, shoots and rhizosphere soil using targeted and untargeted metabolomics.
The first part of the study focused on the methodology in flavonoid identification and quantification in lupin (Lupinus angustifolius L.) root and soil samples in a field experiment using a targeted approach when intercropped with barley (Hordeum vulgare L.). Instrument and sample-specific parameters were validated prior to sample analysis. Different soil extraction methods were evaluated to achieve a satisfying recovery for as many compounds as possible. In total, four flavonoids were exuded from lupin roots into the soil. Large variations were observed, possibly due to local biotic or abiotic factors within the field. A pot experiment was conducted under semi-field conditions to investigate the potential changes in flavonoid concentration in barley and lupin as a response to intercropping. In the second part of the study, untargeted metabolomics (LC-QTOF MS) was applied to annotate unknown compounds in lupin, which were affected by intercropping. The experiment allowed for the annotation of six compounds in lupin: five flavonoids increased in concentration as a response to intercropping, whereas tryptophan concentration was reduced. The samples were analysed using GC-TOF MS to investigate mainly primary metabolites, which turn volatile and easy to analyse in GC by derivatisation. The statistical analysis did not show any significant changes in concentration for any of the detected chemical compounds. Most literature on legume-cereal intercropping is focused on the legume and how the legume metabolome is affected by intercropping. The third part, therefore, consisted of a targeted analysis of lupin and barley to elucidate the effect of intercropping on both crops and to get a better understanding of the changes in flavonoid concentrations. The results showed that the effect on lupin flavonoids was less significant in a pot experiment than on barley. In barley shoots; genistein, rutin and apigenin increased in concentration due to intercropping. These results displayed the two-way impact of neighbouring crops on flavonoid composition and concentration.
Overall, this PhD study has improved our knowledge about lupin and barley flavonoids and how intercropping changes the flavonoid composition and concentration in the crops. These findings form the basis for further intercropping research utilising legumes and their many environmental benefits. Increased flavonoid concentrations can for example improve pest resilience, weed suppression and grain yield and should be considered in our agricultural production to support the green transition.
The first part of the study focused on the methodology in flavonoid identification and quantification in lupin (Lupinus angustifolius L.) root and soil samples in a field experiment using a targeted approach when intercropped with barley (Hordeum vulgare L.). Instrument and sample-specific parameters were validated prior to sample analysis. Different soil extraction methods were evaluated to achieve a satisfying recovery for as many compounds as possible. In total, four flavonoids were exuded from lupin roots into the soil. Large variations were observed, possibly due to local biotic or abiotic factors within the field. A pot experiment was conducted under semi-field conditions to investigate the potential changes in flavonoid concentration in barley and lupin as a response to intercropping. In the second part of the study, untargeted metabolomics (LC-QTOF MS) was applied to annotate unknown compounds in lupin, which were affected by intercropping. The experiment allowed for the annotation of six compounds in lupin: five flavonoids increased in concentration as a response to intercropping, whereas tryptophan concentration was reduced. The samples were analysed using GC-TOF MS to investigate mainly primary metabolites, which turn volatile and easy to analyse in GC by derivatisation. The statistical analysis did not show any significant changes in concentration for any of the detected chemical compounds. Most literature on legume-cereal intercropping is focused on the legume and how the legume metabolome is affected by intercropping. The third part, therefore, consisted of a targeted analysis of lupin and barley to elucidate the effect of intercropping on both crops and to get a better understanding of the changes in flavonoid concentrations. The results showed that the effect on lupin flavonoids was less significant in a pot experiment than on barley. In barley shoots; genistein, rutin and apigenin increased in concentration due to intercropping. These results displayed the two-way impact of neighbouring crops on flavonoid composition and concentration.
Overall, this PhD study has improved our knowledge about lupin and barley flavonoids and how intercropping changes the flavonoid composition and concentration in the crops. These findings form the basis for further intercropping research utilising legumes and their many environmental benefits. Increased flavonoid concentrations can for example improve pest resilience, weed suppression and grain yield and should be considered in our agricultural production to support the green transition.
| Originalsprog | Engelsk |
|---|
| Forlag | Århus Universitet |
|---|---|
| Antal sider | 120 |
| Status | Udgivet - sep. 2023 |