U.S. Science Directed To Meet Challenges to the Global Food System

As population growth and increased demands for more and healthier foods increases the challenges of efficient and sustainable production grow as well. Predicted changes in weather patterns as a consequence of global climate change will place both abiotic and biotic stresses on crop production. Significant effort is being made to increase tolerance to higher temperatures and changes in rainfall. Somewhat less attention is given to changes in pests and pathogens that are expected to increase the threats to agriculture in traditionally temperate climate zones; there will likely be even greater challenges in tropical regions than temperate climates. It is not surprising that changes in global climate are predicted to substantially increase crops losses due to pests and pathogens; some have predicted increases as high as 25%.

Among the diseases that are especially severe in tropical agriculture zones are plant viruses: a myriad of virus disease agents are transmitted by many different types of insect vectors, most of which are referred to as ‘piercing/sucking insects’. Virus are common in vegetatively propagated plants such as cassava and sweet potato and are less common in seeded crops; most viruses have hosts that are weeds commonly found in and around cultivated areas. During the past 25 years genetic engineering strategies have been developed to control different types of viruses, including pathogen derived resistance and use of genes that encode host factors for transcription and translation. Pathogen derived resistance makes use of genes that encode viral coat proteins or small interfering RNAs (RNAis) that target regions of the viral genome to provide resistance. With support of foundations, USAID, private companies and other supporters, significant progress has been made by public sector researchers to develop disease resistant varieties of subsistence crops, including cassava, sweet potato, and groundnut, other horticulture and fruit crops and grain crops. The ease of adoption of pathogen derived resistance technologies make disease resistance readily accessible to control most virus diseases (RNAi strategies are also effective to control some fungal pathogens.) Benefits of resistant varieties include reduced costs for the insecticides that transmit the pathogens, increased harvest index, and lower predisposition of plants to other disease agents.  The current challenge is to work with regulatory agencies (in developed and developing economies) to test and approve the new varieties. Unfortunately the time and costs to release most resistant varieties is greater than the value of the seed materials. We propose a rationalized review process for pathogen derived resistance strategies that substantially decreases the time and costs associated with deregulating resistant crop varieties. This will increase food production at little or no environmental risk, while reducing the use of insecticides, each of which are accepted as factors of sustainable agriculture.