PI: Brett Tyler (Virginia Polytechnic Institute and State University)
CoPIs: Shunyuan Xiao (University of Maryland Biotechnology Institute) and Mark Guiltinan (Pennsylvania State University)
Collaborator: Brian Bailey (USDA-ARS Sustainable Perennial Crops Lab, Beltsville, Maryland)
Small-holder agriculture in developing countries is exceptionally susceptible to fungal and oomycete disease due to lack of local breeding programs, tropical climate, abundant insect vectors, cost of and poor access to fungicides, and lack of farmer education. Small-holder farmers in Africa and South America are responsible for more than 95% of cacao production, providing economic benefits to millions of cacao farmers and their dependents, as well as important ecological benefits such as rain-forest preservation. Fungal and oomycete diseases have devastated cacao production in South America and West Africa, dislocating populations of farmers and resulting in destruction of the rain-forest sheltering the cacao trees in favor of large-scale open farmland. This project will test two novel approaches to protecting developing country crops against a broad-spectrum of oomycete and fungal pathogens, using cacao as the initial target. The first involves targeting anti-microbial proteins to pathogen feeding structures called haustoria, using RPW8, an Arabidopsis protein that has a natural affinity for these feeding sites. The second approach involves blocking the entry of virulence proteins (effector proteins) that pathogens secrete into host cells to suppress the plant host's immune system. The most effective strategies will be identified first using fast growing Arabidopsis and tomato plants before being tested in cacao.
Broader Impacts: The novel technologies that will be tested in this project are potentially applicable to an extremely broad array of crop diseases important to the developing world. The most destructive diseases of broad acreage staples such as rice and wheat are potentially amenable to this approach, as are many of the most limiting fungal and oomycete diseases of crops of importance to smallholders, such as yams, cassava, groundnuts, pearl millet, finger millet, sorghum, maize, potato, bean and cowpea. The project includes visits from scientists from developing countries, a colloquium in Ecuador, and regular communication with scientists from cacao-producing countries. Project outcomes as well as access to biological resources that include DNA constructs and germplasm will be disseminated through a project website (accessible via www.vbi.vt.edu/faculty/research_groups/brett_tyler) and through publications.
Intellectual Merit: This project tested two entirely novel genetic approaches to protecting developing country crops against a broad-spectrum of fungal pathogens and oomycete pathogens (fungus-like algal parasites), using cacao as the initial target. One of the novel approaches involved targeting anti-microbial proteins to pathogen feeding structures using a protein from thale cress that has a natural affinity for these feeding sites. The second novel approach involved blocking the ability of virulence proteins that are produced by pathogens to suppress the plant host’s immune system. The protein from thale cress conferred disease resistance in thale cress when fused to several anti-microbial proteins, but did not work in cacao or tomato, perhaps because it did not recognize feeding structures in those plant species. The second approach of blocking pathogen virulence proteins worked very well in cacao. Cacao leaves were strongly protected against several destructive oomycete and fungal pathogens. Some data were obtained suggesting that the approach may work in rice also. Broader Impacts: Small-holder agriculture in developing countries is exceptionally susceptible to fungal and oomycete disease due to lack of local breeding programs, tropical climate, abundant insect vectors, cost of and poor access to fungicides, and lack of farmer education. Small-holder farmers in Africa and South America are responsible for more than 95% of cacao production, providing economic benefit to millions of cacao farmers and their dependents, as well as important ecological benefits such as rain-forest preservation. Fungal and oomycete diseases have devastated cacao production in South America and West Africa, dislocating populations of farmers and resulting in destruction of the rain-forest sheltering the cacao trees in favor of large-scale open farmland. The promising disease resistance technology that was evaluated in this project is potentially applicable not only to cacao, but also to an extremely broad array of crop diseases important to the developing world. The most destructive diseases of broad acreage staples such as rice and wheat are potentially amenable to this approach, and also many of the most limiting fungal and oomycete diseases of crops of importance to smallholders, such as yams, cassava, groundnuts, pearl millet, finger millet, sorghum, maize, potato, bean and cowpea. The project also included training visits from five scientists from developing countries to the project team at Pennsylvania State University, and a visit by the project team to cacao-growing areas of Ecuador to learn more about the practical problems involved in dealing with cacao diseases.
