Engineering Broad-spectrum Disease Resistance

The global production of agricultural and food products is the world’s largest industry, with total revenues of ~$5 trillion (US) per year. Diseases caused by phytopathogens are economically important, resulting in multibillion-dollar losses annually, and it has been estimated that more than 25 % of all crop plants worldwide are lost to fungal, bacterial, and viral diseases. In the developing world, up to 40 % of all crop destruction can be directly attributed to plant diseases, with occasional catastrophic, life-threatening losses. The increased reliance on chemical solutions to diseases has compromised environmental quality, engendered a negative impact with consumers, and resulted in a rise of fungicide resistant microorganisms. Conventional breeding, though relatively successful in the development of disease resistant plant cultivars, has become increasingly difficult because of the limitations of resistance genes within usable gene pools. However, advances in plant genetic engineering have facilitated the integration of beneficial “designer ” genes into plants. This technology has been successfully applied to generate plant resistance to herbicides, some insects, and occasionally some phytopathogens. Strategies to improve the health of crops through genetic engineering have included transgenic expression of plant, fungal, or bacterial hydrolytic enzymes, pathogenesis-related proteins, components of plant defense-response pathways, antimicrobial proteins, and peptides. Although food safety is of utmost importance and disease resistant plants are required, the commercial application of this technology is lagging. The protection offered in some cases is limited to specific diseases, which means other pathogens can thrive and plants must still be sprayed with fungicides