Our lab members are engaged in a wide range of projects that are generally focused on identifying traits and management practices to increase grapevine resource-use efficiency and mitigate the impacts of stress on grape yield and quality. Our major research themes include:

Identifying traits to improve drought tolerance in grape rootstocks

Drought tolerant rootstocks are an important management tool for grape growers to reduce irrigation use and maintain yield and quality under dry conditions. One of the goals of our research is to facilitate rootstock breeding by identifying the key physiology traits underlying belowground drought tolerance and developing rapid genetic and phenotypic proxies to screen for these traits across many accessions or genotypes. Our current work is focused on evaluating the potential for traits characterizing drought responses in the living tissues of the root to improve whole-plant drought performance. Most research has focused on the specialized water transport tissues – the xylem – while new advances in imaging suggest that the living tissues that radially transport water from the soil to the xylem are the major bottleneck on plant water uptake under drought. Our work seeks to identify the genetic, anatomical, and biochemical drivers and develop rapid phenotyping methods for these traits.

Optimizing grapevine stomatal behavior for future environmental conditions

The stomata – small pores on the leaf surface – regulate photosynthesis and evapotranspiration, which determine plant water stress, water-use efficiency, and resource availability for growth and ripening. Under hot or dry conditions, plants must resolve conflicting demands between keeping the stomata open to maintain photosynthesis and evaporative cooling and closing the stomata to conserve water and avoid severe water stress. We use experimental work and plant optimization models to identify the stomatal traits that would maximize water savings under future environmental conditions without excessive limitations on canopy cooling or carbon availability for ripening. Part of this work is focused on osmotic adjustment – the accumulation of solutes in the cells under water stress – a plasticity mechanism nearly all plant species use to improve leaf drought tolerance. Osmotic adjustment protects cell structural integrity, helping plants avoid stomatal closure, wilting, and hydraulic failure (disrupted water transport). Osmotic potential is also one of the few drought-related traits feasible for rapid phenotyping. Our research seeks to evaluate whether selection for osmotic adjustment is a promising strategy to achieve optimal stomatal traits in grape breeding.

Mechanisms governing the responses of sugar transport to environmental stress

Under climate change, winegrowers are facing a mismatch in ripening, where sugars, acids, and tannins no longer reach ideal concentrations at the same time. Heat and drought accelerate sugar accumulation, so growers are forced to harvest early, before tannins are ripe, or risk the bland, overly alcoholic wines produced by excessive sugar. We use experimental work and biophysical models of the sugar transport tissue – the phloem – to evaluate how sugar transport is coordinated with hydraulics and gas exchange, and how diversity in phloem anatomy and molecular biology impacts sugar transport in water-stressed vines. These traits could be targeted through breeding or even genetic engineering to manipulate sugar accumulation in the berries.