What plant metabolomics has to offer weed biocontrol
In this section
The metabolome is the term describing the combined metabolic profile/phenotype as expressed by an organism or a tissue. Environmental conditions influence the metabolites produced by organisms/tissues, thus a given species will express different metabolomes in different environments. A 2021 review assessed how we can use metabolomics, the study of metabolomes, to advance weed biocontrol. Three aspects were identified:
The first aspect has to do with matching weed metabolomes between agent collection sites in the native range and agent release sites in the introduced range. Even without knowing the exact environmental factors that led to the similarity in metabolic phenotype expression between the two ranges, just knowing that the metabolic phenotypes are similar is likely to mean that the chemical defence profile and nutritional profile of the weed at the chosen release site should be able to support agent establishment as well as at the site it has been collected from. In other words, the weed’s metabolome serves a surrogate to predict suitability of that environment for the agent, thus increasing chances of successful establishment.
Secondly, analysing the weed’s metabolome in response to attack by an agent can tell us if the weed does indeed become stressed in response to a particular species or feeding guild of herbivores/pathogens. This is useful to inform agent selection process and help to identify if additional agents are required, and which feeding guilds they should come from. Importantly, studying the plant metabolome in this way can indicate if certain natural enemies can only induce plant defence response if they are combined with another natural enemy from a certain other guild, and would be ineffective if released on their own.
Thirdly, metabolomics hold the potential to assist testing for host range and specificity in two ways: by identifying plant species that share similarities with the target weed in their metabolomes, and which would otherwise have been overlooked because they are phylogenetically distant from the target weed; and by enabling testing of phylogenetically related species, or other species of interest, that are difficult to obtain (e.g. rear/threatened native species), through using their metabolome as a proxy instead of using the actual plant.
Overall, the potential for adding metabolomic analysis to the toolkit will undoubtedly contribute to greater effectiveness and safety of weed biocontrol programmes. At the time of writing, these tools are still too early in their development and are too costly to include in routine risk assessment and decision making in weed biocontrol, but it may be not too long before this powerful technology becomes part of weed biocontrol routines.