Differential physiological responses of resistant and susceptible grape cultivars to Eutypa dieback

Authors: SINCLAIR, GABRIELA - University Of California, Davis; TRAVADON, RENAUD - University Of California, Davis; Eschen, Paula; Wallis, Christopher; Baumgartner, Kendra; DELMAS, CHLOE - Inrae; HNIZDOR, JOSHUA - University Of California, Davis; BARTLETT, MEAGHAN - University Of California, Davis

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2025
Publication Date: 3/18/2025
Citation: Sinclair, G.C., Travadon, R., Eschen, P., Wallis, C.M., Baumgartner, K., Delmas, C.E., Hnizdor, J.F., Bartlett, M. 2025. Differential physiological responses of resistant and susceptible grape cultivars to Eutypa dieback. Journal of Experimental Botany. Article eraf103. https://doi.org/10.1093/jxb/eraf103.
DOI: https://doi.org/10.1093/jxb/eraf103

Interpretive Summary: Eutypa lata causes a devastating disease called Eutypa dieback that affects grapevines worldwide. However, little is known about how infections progress, and what mechanisms grapevines may possess innately to tolerate the resultant disease. Thus, host physiological and biochemical factors were assessed when E. lata infected a tolerant (Zinfandel) and susceptible (Syrah) grapevine cultivar. Syrah had greater lesion lengths, more anti-fungal compound production, and higher gas exchange rates when infected than Zinfandel. This suggests the susceptible cultivar responded with a stronger host response to infection, which was hypothesized to be the result of greater susceptibility to E. lata produced toxins. Therefore, monitoring physiological and biochemical changes that novel grapevine selections have when infected by E. lata will help determine relative susceptibility.

Technical Abstract: Eutypa lata, the main causal agent of Eutypa dieback, causes widespread economic damage and threatens vineyard longevity worldwide. Thus, a study was initiated to further understanding of how grapevines resist E. lata infections. To do this, a tolerant (Zinfandel) and a susceptible (Syrah) cultivar were inoculated with E. lata, and gas exchange, hydraulic conductivity, fluorescence (Fv/Fm), leaf chlorophyll content, pre-dawn leaf and midday stem water potentials, osmotic potential, lesion lengths, root biomass, canopy area, and wood chemistry were measured. Syrah exhibited longer lesion lengths and had greater levels of certain total mean wood anti-fungal compounds, higher gas exchange rates, and photochemical functioning than Zinfandel. There were no significant treatment effects on osmotic potential, lesion length, root biomass, canopy area, lignin content, or overall phenolic concentrations. These findings suggest that the impacts of infection on gas exchange were more strongly determined by E. lata produced toxin effects on leaf photosynthetic biochemistry than direct pathogen effects on hydraulics or osmotic adjustment. These results reveal novel approaches to rank cultivars in susceptibility to E. lata, as varieties that can maintain photoassimilate production should be prioritized in breeding programs as these may be more resistant.