Minority grapevine varieties as climate change adaptation strategy: Exploring heat tolerance plasticity

Climate change is increasing average temperatures and intensity and frequency of extreme events such as heat waves. Productivity declines and plant damage due to those changes are already described for several majority varieties, especially in the Mediterranean basin. Less explored minority varieties can arise as alternatives due high heat tolerance, or for having high acclimation potential to heat. We evaluated the heat tolerance after acclimation in three summer thermic environments of four Spanish varieties: two majority (‘Tempranillo’, ‘Airén’) and two minority (‘Jarrosuelto’, ‘Morate’). Summer thermic environments differed in average temperature, and length of the warm period. Varieties differed in heat tolerance and its plasticity due to the acclimation to the environments. Within the majority varieties, ‘Tempranillo’ showed low heat tolerance and moderate plasticity in heat tolerance highlighting its susceptibility to climate change. ‘Airén’ had slightly higher tolerance than ‘Tempranillo’ and certain adaptation capacity to environments. Within the minority, ‘Jarrosuelto’ had high tolerance to heat events but low heat tolerance plasticity. ‘Morate’ was the variety with highest heat tolerance plasticity, indicating its strong adaptive potential. Majority varieties displayed susceptibility to heat events and global warming negative effects. However, minority varieties can offer solutions either by having high tolerance to heat or by having high acclimation.

Relationship Between the Xylem Anatomy of Grapevine Rootstocks and Their Susceptibility to Phaeoacremonium minimum and Phaeomoniella chlamydospora

Fungal grapevine trunk diseases (GTDs) are some of the most pressing threats to grape production worldwide. While these diseases are associated with several fungal pathogens, Phaeomoniella chlamydospora and Phaeoacremonium minimum are important contributors to esca and Petri diseases. Recent research has linked grapevine xylem diameter with tolerance to Pa. chlamydospora in commercial rootstocks. In this study, we screen over 25 rootstocks for xylem characteristics and tolerance to both Pa. chlamydospora and Pm. minimum. Tolerance was measured by fungal incidence and DNA concentration (quantified via qPCR), while histological analyses were used to measure xylem characteristics, including xylem vessels diameter, density, and the proportion of the stem surface area covered by xylem vessels. Rootstocks were grouped into different classes based on xylem characteristics to assess the potential association between vasculature traits and pathogen tolerance. Our results revealed significant differences in all the analyzed xylem traits, and also in DNA concentration for both pathogens among the tested rootstocks. They corroborate the link between xylem vessels diameter and tolerance to Pa. chlamydospora. In Pm. minimum, the rootstocks with the widest xylem diameter proved the most susceptible. This relationship between vasculature development and pathogen tolerance has the potential to inform both cultivar choice and future rootstock breeding to reduce the detrimental impact of GTDs worldwide.