The Food and Agriculture Organization of the United Nations (FAO) predicts that food production will have to increase 70% by the year 2050 to meet the needs of the approximately 9 billion people expected to live on the Earth.1 Much of the projected growth in population will occur in Asia and sub-Saharan Africa.3 Unfortunately, crop yield improvement projections do not, at present, meet this goal, particularly in sub-Saharan Africa.2,3 One important goal to meet the projection is to reduce the loss of yield in food crops due to disease. One third of crop yield potential is, in general, lost to disease, and two thirds, on average, is lost when adequate crop protection is unavailable. Improvements also have to come in concert with significant changes in climate, water resources, and land availability.4
Rice is the world's third largest crop after maize and sugarcane, and an important staple crop for many developing countries of Asia and Africa. Our goal is to increase food security and food availability by decreasing pathogen susceptibility of the rice crops in Africa and Asia using translational knowledge derived from the basic science of disease molecular biology. Crops with decreased susceptibility to pathogens will produce more reliable and higher yield and require less pesticide use. Bacterial blight disease of rice results in yield losses in Asia approaching 60% annually.5 With the introduction of Asian rice varieties to Africa, blight is also expected to become a major challenge in African countries. Under the right environmental conditions, a bacterial blight epidemic in rice can destroy the entire crop, creating food instability and leading to immense losses, especially for subsistence farmers. No effective pesticide management strategy exists for preventing or alleviating disease in the field. The most effective and environmental-friendly way is to breed for genetic resistance. At the same time, traditional resistance gene deployment from wild rice or inferior cultivars is a time-consuming process, and resistance can be overcome by new pathogen strains.
We propose to produce new breeding lines for rice available to breeders and farmers in Africa and Asia with broad durable resistance to bacterial blight based on knowledge of the molecular and genetic details of the disease. Bacterial blight is caused by the γ-proteobacterium Xanthomonas oryzae pathovar oryzae (Xoo). The bacteria hijack host nutrients by creating leaks in cellular sugar content. The bacteria enable leakage by secretion of transcription factors, known as TAL effectors, that direct the expression of host genes whose protein products are sugar pores in the host cells. We have developed strategies to prevent TAL effector dependent sugar release using genomic editing of rice and are introducing the new traits into elite rice lines. Our approach is focused on the introduction of mutations into rice lines Kitake, IR64, and Ciherang-Sub1. This work would lay the basis for introducing these traits into multiple countries in Asia and Africa. Ciherang-Sub1 has been released in Bangladesh and India. IR64 is breeding-ready variety for introducing resistance to Makassane and Komboka, which have been released in Mozambique and Tanzania, respectively.
2. Ray DK, Mueller ND, West PC, Foley JA (2013) Yield Trends Are Insufficient to Double Global Crop Production by 2050. PLoS ONE 8(6): e66428.
3. Cereal Yields: Derived from FAO. 2012. “FAOSTAT.” Rome: FAO; graph by IFDC.