Graft-transmitted induced resistance for tomato crops using priming agents

Overview

This research proposes an innovative strategy to deliver long-lasting induced resistance in tomato crops by exploiting the natural graft junction between rootstock and scion. Priming agents (PAs) such as β-amino butyric acid (BABA) are powerful tools that activate defence mechanisms against pests and pathogens, but their commercial use has been limited by associated fitness costs, including reduced growth and yield. Preliminary evidence suggests that while these negative effects are temporary, the induced resistance is stably maintained through the plant's life, expressed in newly developed tissues, and even inherited by the next generation. By applying PAs only to rootstocks, which fully recover from any growth reduction before grafting, the long-lasting resistance can be transmitted to untreated scions, providing an efficient and economic disease management solution for commercial horticulture.

Technical specifications

Key features:

• Priming agent application: Rootstocks are treated with β-amino butyric acid (BABA), a well-characterised priming agent that triggers broad-spectrum defence responses.
• Epigenetic mechanism: DNA methylation changes induced by BABA have been identified through omics approaches, distinguishing between loci responsible for transient growth reduction and those maintaining long-lasting resistance.
• Graft-transmissible resistance: Long-lasting induced resistance can cross the graft junction from treated rootstocks to naive scions, while fitness costs remain confined to the rootstock.
• Multi-pathogen protection: BABA-induced resistance targets multiple pathogens, including Botrytis cinerea, a major fungal threat in tomato production.
• Compatibility testing: Validation includes both model cultivars (Microtom and Heinz homo-grafts) and commercial inter-cultivar combinations, with potential input from seed-industry companies.

Validation approach:

• Measurement of plant fitness parameters including size and internodal growth.
• Assessment of fruit production metrics including ripening times, fruit number, fruit weight, and sugar content.
• Disease challenge assays against Botrytis cinerea on leaves and detached fruit.
• Genomic analysis to identify loci associated with graft-transmitted long-lasting resistance.

Technology readiness level

This technology is at an early-to-mid stage of development. The underlying biological mechanism has been established through omics-based research demonstrating that BABA-induced DNA methylation changes separate resistance traits from fitness costs. The core concept, that long-lasting resistance is transmissible through grafting while growth penalties are not, is supported by preliminary data but has not yet been validated in grafted plants. Current work involves testing BABA-treated rootstocks paired with naive scions across model and commercial tomato cultivars. Further validation is needed to confirm resistance transmission, quantify effects on yield and fruit quality, and identify the genetic loci responsible before commercial deployment can be considered.