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HHU-led research consortium expanded by four additional institutions to defeat bacterial rice blight, one of the main challenges for smallholder farmers

(Photo: Healthy rice plants in Telangana, India © Yugander Arra)

The “Healthy Crops” project, headed by Alexander-von-Humboldt Professor Wolf B. Frommer from Heinrich Heine University Düsseldorf (HHU), has developed a strategy to combat “bacterial leaf blight” (BLB), one of the most devastating rice diseases in large parts of Asia and Africa. BLB has significant impact on small scale producers in low and middle-income countries. The recent extension of the project funding is accompanied by the introduction of new scientific partners, in particular from ICAR institutes in India and IRRI partners from Kenya and the Donald Danforth Plant Science Center. The project’s mission is to deliver BLB-resistant rice lines to smallholders in Asia and Africa.

The “Healthy Crops” team, funded by the Bill & Melinda Gates Foundation, started in 2012 with the concept of generating rice variants resistant to “bacterial leaf blight”, thereby providing an effective and sustainable solution for yield losses especially for small scale producers in developing countries. The team has already successfully generated BLB-resistant rice lines and created a diagnostic toolbox that enables a rapid disease diagnosis of the newly occurring pathogenic bacterial strains (both published in 2019 in Nature Biotechnology).

Rice is the world’s most important staple food for around 4 billion people worldwide and is mainly cultivated by small scale producers in low and middle-income countries. BLB, caused by the bacteria Xanthomonas oryzae pathovar oryzae (Xoo), is a major problem in the cultivation of rice and can result in yield losses of up to 70 percent. Infection causes wilting, desiccation of leaves and subsequently in the death of the plants. This has a massive impact on the smallholder’s economic stability. A problem that Ashok K. Singh, the director of the ICAR-IARI in India knows very well: “Bacterial blight is one of the most serious rice diseases in India and other parts of the world. The yield losses in India vary from 15-20 % annually and can reach up to 40 % in case of severe infection in susceptible varieties. Healthy Crops has developed highly valuable rice variants resistant to BLB. To defeat the disease, we aim to introduce the resistance into the elite mega rice varieties of India.

The original consortium coordinated through the Heinrich-Heine-University (HHU) includes five research institutes on four continents: The University of Florida and University of Missouri in the USA, the International Center for Tropical Agriculture (CIAT) in Colombia, the Institut de Recherche pour le Développement (IRD) in France and the International Rice Research Institute (IRRI) in the Philippines are involved in the project. Four important research institutions were added in 2020, from India, Kenya and the USA. Healthy Crops will now be strengthened by two institutions of the Indian Council of Agricultural Research (ICAR), the Indian Agricultural Research Institute (IARI) and the National Rice Research Institute (NRRI) in India, the African IRRI branch in Nairobi, as well as the Donald Danforth Plant Science Center. 

The mechanism by which Xoo gains access to the plant’s nutrition was the key in the development of their strategy. Once infected, Xoo injects a set of proteins, the so-called TAL-effectors, into the host cell. The TAL-effectors bind to the regulatory domains of SWEET sugar efflux transporter genes, thereby inducing the release of sugars from the infected rice cells. The Xoo bacteria use the released sugar as energy source for their own replication.

Interestingly, in the past, Japanese breeders found that some natural rice varieties were resistant to certain Xoo strains. The SWEET promoter cannot be recognized by the TAL-effectors in these varieties. This prevents the bacteria from forcing sugar secretion, resulting in Xoo resistant rice plants.

BLB infected rice field in Telangana, India © Yugander Arra

These findings enabled the consortium to introduce resistant rice varieties, which will help smallholder farmers worldwide in their fight against bacterial blight. “Rice production and consumption in Sub-Saharan Africa is showing an unprecedented increase over the past decades. At the same time, bacterial plant diseases are expanding rapidly in the rice producing areas. The development of resistant varieties, ahead of the evolution of new pathogenic strains, will lead to stable production and protect smallholder farmers from yield losses”, explains Abdelbagi Ismail, the IRRI representative for Africa.

The expansion of the team and the integration of the new international partners enables Healthy Crops to pave the way towards development of new BLB-resistant rice varieties. The project is strictly non-profit, aiming to improve the livelihood and income of small-scale producers and farmers around the world.

This research is supported by funds from the Bill & Melinda Gates Foundation to HHU.

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