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JAN LEACH, 2019 Agropolis Fondation Louis Malassis Distinguished Scientist Prize

Tipping the balance: Long-lasting disease resistance to multiple pathogens

With the expectation that the world’s population will increase by 2.4 billion people within 35 years, global food production needs to increase by 70%. At the same time, an astonishing 10-40% of major food crops are lost worldwide due to diseases and pests.

Climate change compounds the issues; with higher environmental temperatures, there are higher levels of diseases in crops. Losses in rice are particularly devastating because of its importance in food insecure regions.

“Over the past 30 years, my research group has worked to improve rice quantity and quality by understanding how rice resists diseases. Our work has helped define how bacterial pathogens cause disease and how plants defend themselves from pathogen attack while simultaneously experiencing other stresses, such as high temperatures. These findings are helping the development of rice with disease resistance that is long-lasting in the field and that is effective against different types of pathogens”, says Dr. Jan Leach, the 2019 laureate of the Agropolis Fondation Louis Malassis International Scientific Prize for Distinguished Scientist.

While initially effective, single resistance genes are frequently short-lived, because changes in the pathogen or environment render the resistance genes ineffective. Then to develop disease resistant rice varieties, “crop improvement programs have long focused on incorporating disease resistance genes,” adds Dr. Leach.

Clearly, to reduce crop losses to disease, new strategies were needed to augment the development of resistant crop varieties.

To address this challenge, Dr. Leach and her international collaborators investigated three questions: “First, we asked ‘why are some resistance genes effective longer in the field than others?’. This line of thinking led to a novel means to predict how long resistance genes would be effective in the field before the long, labor-intensive process needed to introduce a gene into widely used crops. Second, we showed that improving how plants respond to pathogens in general (called basal or quantitative resistance) provides long-lasting resistance that is effective against multiple pathogens. Third, we asked ‘why are plants more susceptible to disease at high temperatures?’ By studying the effects of simultaneous disease and heat stress, we identified genes that will enable crop breeders to improve crop resilience to combined disease and high temperature stresses”, notes Dr. Leach. Collectively, this work has provided information, tools and resources that guide disease resistance breeding.

A critical piece to improving worldwide food security is the reduction of crop losses caused by diseases. Early on, Jan and her team embraced the complexity of simultaneous stresses, showing that heat stress increases disease susceptibility in rice, and identifying resistance sources that are more effective at elevated temperatures. Their focus now is to develop the foundational mechanistic information needed to deal with disease in face of a changing climate.

Solving agriculture’s grand challenges will require a well-trained, international workforce and will benefit from robust collaborations. “I have been privileged to train many excellent scholars who now hold positions in international research centers, universities, industries, and governments. These scholars as well as many international collaborators from institutions like the International Rice Research Institute and IRD – Institut de Recherche pour le Développement (France) – contributed to the work honoured by the Malassis International Prize. I am proud that these amazing scientists continue the quest to stabilize agriculture in a world that is facing tremendous environmental challenges, and my hope is that they enjoy the process as I have”, says Dr. Leach.

Dr. Leach is Plant Pathologist. She is currently the Research Associate Dean of the College of Agriculture at the Colorado State University (USA).