Evaluating the Impact of Plant Activator Compounds on Pest and Pathogen Resistance, and Plant Development in Solanum lycopersicum Across Short, Medium, and Long-Term Periods

Ponce-Ponce de Leon, Cesar Alejandro and Roberts, Mike and Toledo-Ortiz, Gabriela (2025) Evaluating the Impact of Plant Activator Compounds on Pest and Pathogen Resistance, and Plant Development in Solanum lycopersicum Across Short, Medium, and Long-Term Periods. PhD thesis, Lancaster University.

Text (2025PoncePhD)
2025poncephd.pdf - Published Version
Restricted to Repository staff only until 2 December 2028.
Download (3MB)

Abstract

The thesis evaluates the effects of full formulations of the commercial plant protection product VirusStop® both in its commercial form (VSSP) and organic form (VSSC), as well as the effects of the individual natural extracts from five different plants that are part of their formulations. In resistance bioassays, VSSC and VSSP were effective against both bacterial and fungal pathogens, but not against a herbivore. Plant Natural Extracts (PNEs) used as individual treatments were not significantly different from the controls, pointing toward a synergistic effect in the VS® formulations. Quantitative real-time PCR (qPCR) was used to analyse samples from VirusStop®-treated plants both with and without pathogen challenge. Both VSSC and VSSP activated expression of genes representing the biosynthesis and signalling pathways for ethylene and jasmonic acid. Both VSSP and VSSC present a typical priming timeline progression with defence gene expressions at 24 hours post-treatment (hpt) and rapid and increased response after the challenge, within 12 hours post-inoculation (hpi). Application of VSSP and VSSC do not show significant impact on overall growth and production of fruit, except for a delay in flowering and fruiting, which had no impact on total fruit production. Overall, this thesis presents evidence of both molecular and pathogen resistance efficacy from both VS® formulations against bacteria and fungi. The results point toward a priming effect from both formulations, with notably upregulated gene expression from VSSP against B. cinerea. No detrimental physiological effects were observed on tomato plants in both the medium- and long-term in glasshouses and controlled environment rooms. This data supports the usage of this product in crops, making VSSP and VSSC effective resistance inducers (RIs) due to the synergistic relationship between the PNEs and other compounds in the formulation.