Current methods of pest and disease control in vegetables largely depend on chemical pesticides and/or single resistance genes. The use of chemical defence activators that prime quantitative disease resistance provides an alternative method to protect crops against pests and diseases. However, previous attempts to exploit this approach resulted in undesirable side effects on plant growth, and did not address durability of the induced protection.
We are developing protocols to reduce vegetable diseases by means of defence priming without major yield penalties. These strategies involve (combinations of) chemical priming agents, beneficial microbes and epigenetic manipulation. Each of these strategies aim to obtain long-lasting disease protection against commercially relevant plant diseases, such as Botrytis cinerea in tomato and Bremia lactuceae in lettuce. Previously, we identified commercially feasible application methods of beta-aminobutyruic acid (BABA) and jasmonic acid (JA), which induce durable disease resistance in tomato without major impacts on plant growth or colonization by plant-beneficial microbes (1). More recently, we discovered a structural analogue of BABA, R-beta-homoserine (RBH), which operates via partially different signalling pathways and is less detrimental to plant growth (2).
In a ERC-funded Proof-of-Concept grant (ChemPrime), we have investigated further seed and seedling treatments of tomato and lettuce with resistance-inducing β-amino acids, aiming to integrate these priming treatments with conventional methods of disease protection, such as multigenic cultivar resistance. In addition, this project has identified novel regulatory genes controlling the trade-off between BABA- and RBH-priming and plant growth. A second work package the ChemPrime involved a stakeholder survey to map out pathways for commercialisation and application of priming chemicals. This identified the need for integrating priming chemicals in existing integrated pest and disease management schemes (3), including for instance the genetic (and potentially epigenetic) selection of crop varieties that respond optimally to priming chemicals as a means to tailor the technology to specific crop species. The survey also identified hydroponic production systems, such as greenhouses and vertical urban farms, are the most viable and obstacle-free route to application, while exploitation of priming chemicals in soil-based production systems requires crop-specific optimisation of slow-release seed coating technology. Lastly, the survey identified the need for cost-efficient synthesis pipelines of priming chemicals to increase potential demand in the crop protection industry. For a summary of the ChemPrime project, see this CORDIS video.
In collaboration with industrial stakeholders (ENZA Seeds) and researchers from the James Hutton Institute, we are continuing to investigate the effectiveness and durability of combinations of chemical priming agents, using hyperspectral imaging techniques to quantify resistance-inducing effectiveness. Furthermore, based on our research on epigenetic regulation of plant immune priming (Maintenance of the ‘primed’ defence state), we are developing adustiable epi-mutagenesis strategies to select for epigenetically primed crop varieties.
References
1. Luna et al. & Ton J (2016). Plant Dis 100: 704-710. 2. Buswell et al. & Ton J (2018). New Phyt 218: 1205-1216. 3. Yassin, Ton J et al. & Newton (2021). Pest Manag Sci DOI: 10.1002/ps.6370.
plant environmental signalling 