Response Doctoral Program

From the Burren in Ireland and the Erins in France to the Alps in Switzerland, grasslands are vital ecosystems that play a crucial role in supporting biodiversity, providing ecosystem services, and ensuring food security. These vast and diverse grasslands are just a few of the many that cover around 17% of the European Union’s total surface area, as of 2018 (EUROSTAT 2021). Grasslands are among the most species-rich habitats on Earth (Petermann and Buzhdygan), home to a wide variety of flora and fauna, and are essential breeding grounds for birds and invertebrates. In addition, they provide numerous ecosystem services such as water purification, soil erosion prevention and carbon sequestration. Grasslands contain various species of forage grasses, crucial for feeding livestock. Forage grasses, such as Lolium spp. and Festuca spp. are valuable, environment-friendly sources of livestock feed. However, frequent and unpredictable droughts have threatened forage grass yields, posing significant challenges to farmers and livestock managers.

To address this issue, it is essential for forage breeders to understand how these grasses respond to drought conditions. Such knowledge can help develop strategies to mitigate the impacts of drought on forage grass production. Reah Gonzales, a doctoral student of the Molecular Plant Breeding group at ETH Zurich and RESPONSE fellow in the PhD program Science and Policy, in collaboration with forage breeders at Barenbrug France, has been studying the physiological and genetic basis of drought tolerance in forage grasses as part of her PhD research.

Forage grass responses to drought

Drought, a major consequence of climate change, reduces grassland production by up to 78%. Drought-induced yield loss in forage grasses results in an annual financial loss of up to 9 billion Euros in the livestock industry. Forage grasses are an environment-friendly source of fodder for livestock, as they can be directly cultivated and stored as hay or silage on farms. Reah focused on two common forage grasses: perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) (Fig. 1). To classify the responses of perennial ryegrass and tall fescue, a panel of elite perennial ryegrass and tall fescue genotypes were screened for their responses to drought. These plants were then genotyped-by-sequencing, and marker trait associations were conducted to genetic markers associated with drought tolerance.

Perennial ryegrass is known to struggle with drought, while tall fescue is more tolerant. The aim of Reah’s study was to expand our knowledge of the physiological and genetic mechanisms that allow tall fescue to tolerate drought, and then develop genetic markers that can be used to breed drought-tolerant forage grasses more efficiently. One of the key findings of Reah’s research is that different species of forage grasses have evolved distinct strategies to cope with drought stress. Tall fescue is a “water saver” that can maintain leaf growth by reducing water loss under water deficit conditions, whereas perennial ryegrass is a “water spender” that uses all available water for growth under optimal conditions but fails to cope under severe stress. Understanding these different strategies can help breeders develop grasses that are better equipped to handle drought. Reah also identified specific genes responsible for drought tolerance in perennial ryegrass. This unveils new possibilities for genetic engineering and marker-assisted selection to develop drought-tolerant forage grass varieties that can withstand changing drought conditions.

High-throughput phenotyping technologies to classify drought responses in forage grasses

Advances in high-throughput phenotyping technologies have resulted in the development of phenotyping platforms that significantly improve the efficiency of plant breeding. These platforms allow for the precise, non-destructive measurement of specific plant physiological traits. High-throughput phenotyping technologies are used alongside statistical models to classify plant responses to both biotic and abiotic stresses. Integrating data from high-throughput phenotyping platforms with modern genotyping technologies has fast-tracked the discovery of novel genes and traits. This integration has also driven the development of remote sensing, imaging, and growth-tracking systems to quantify plant responses to various stresses.

In this study, Reah used high-throughput phenotyping platforms to measure the leaf elongation rate and transpiration rate of perennial ryegrass and tall fescue under drought conditions (Fig. 2). Leaf elongation and transpiration rates are key physiological indicators of genotype-specific adaptability to drought stress. To achieve this, Reah designed two high-throughput phenotyping platforms. The leaf-tracking phenotyping platform is a novel method for determining the points at which leaf elongation slows and eventually arrests under drought stress.

Stakeholder collaboration

Reah collaborated with her secondment partner, Barenbrug, by visiting their facility in Mas Grenier, France and engaging with them for a period of 12 months. Her goal was to ensure that the findings of her research can be implemented in elite breeding programs. As an international forage breeding company, Barenbrug provides an excellent platform for the distribution of drought-tolerant forage grasses, ensuring that farmers can continue producing sustainable forages despite future climate changes. The results of this project will form the basis for developing Kompetitive Allele-Specific Polymerase Chain Reaction (KASP) markers for use in marker-assisted breeding of drought-tolerant forage grasses. Reah’s research has significant implications for the sustainability of livestock production and represents a crucial step towards developing resilient grasslands capable of thriving under changing climatic conditions.

During her stay at Barenbrug in Mas Grenier, France, Reah participated in the day-to-day breeding activities of the company. There, she learned that trust and teamwork are essential to succeed in a breeding program.  

This article is co-authored by Reah Gonzales and Mary Ann George (University of Zurich, RESPONSE Program office assistant).