The international Healthy Crops consortium has developed an innovative strategy to combat the disease bacterial blight (for short: BB) in rice using genome editing technology. If approved for use by farmers in Kenya, the BB-resistant rice varieties are expected to reduce yield losses associated with the disease in the affected rice growing regions and increase productivity. The work is a collaboration between Kenya Agricultural and Livestock Research Organization (KALRO) and Heinrich Heine University Düsseldorf (HHU).
Rice production is of central importance for food security and economic development in many countries, in particular in low- and medium-income countries. Rice is the second most important staple food in East Africa, with 1.8 million tonnes consumed every year in the countries of the East African Community (for short: EAC).
In 2019, members of the Healthy Crops team identified an outbreak of BB in Tanzania caused by invasive Asian variants of the bacterium Xanthomonas oryzae pv. oryzae (Xoo). The bacterium is spreading rapidly and causing estimated yield losses of 13–20%.
Dr. Emily Gichuhi from KALRO explains, “Due to climate change, incidences of rice diseases including BB have been on the rise in Kenyan rice growing areas. This has increased the cost of production among rice farmers, thereby reducing their returns.”
Dr. Daigo Makihara and Dr. Moto Ashikari from Nagoya University (NU) in Japan, researchers from the Wonder Rice Initiative for Food Security and Health (WISH), are working closely with Dr. Gichuhi and her team to develop new African rice varieties. Dr. Makihara explains, “As a result of the international spread of different crop plant varieties, we are increasingly finding ourselves confronted with outbreaks of plant diseases in regions where they have not previously played a role.”
The starting point for the researchers from Healthy Crops is the nutrient supply of the bacteria. The Xoo bacteria possess a set of “keys” which can open the “pantry” of the plants: When the bacterium injects one of these “key” proteins into rice cells, it leads to increased production of a transporter, which releases sugar in the neighborhood of the bacteria. This sugar serves as nutrition and is essential for the multiplication and virulence of the bacteria. However, when the bacteria utilize the sugar, there is none left for the plant, which ultimately dies as a result.
The research team has succeeded in changing the “locks” via genome editing, making the plants resistant to all known Xoo strains currently prevalent in Asia and Africa.
Professor Bing Yang, University of Missouri, who developed the editing approach, states: “The combination of two different sets of enzymes for editing enabled us to develop a robust resistance.”
The import of these edited elite rice varieties has been made possible due to the availability of genome editing guidelines developed by the National Biosafety Authority (NBA) of Kenya and published in 2022.
Dr. Marcel Buchholzer, coordinator of the Healthy Crops project at HHU, explains, “It is now possible to evaluate these rice lines, developed using advanced biotechnology methods at HHU, in Kenya.”
Professor Dr. Wolf B. Frommer, spokesperson for the project at HHU explains, “This project aims to protect smallholder farmers from crop yield losses through knowledge-based approaches to fighting plant diseases.”