Toward a quarter century of pathogen-derived resistance and practical approaches to plant virus disease control.

The concept of pathogen-derived resistance (PDR) describes the use of genetic elements from a pathogen's own genome to confer resistance in an otherwise susceptible host via genetic engineering [J. Theor. Biol. 113 (1985) 395]. Illustrated with the bacteriophage Qbeta in Escherichia coli, this strategy was conceived as a broadly applicable approach to engineer resistance against pathogens. For plant viruses, the concept of PDR was validated with the creation of tobacco plants expressing the coat protein gene of Tobacco mosaic virus (TMV) and exhibiting resistance to infection by TMV [Science 232 (1986) 738]. Subsequently, virus-resistant horticultural crops were developed through the expression of viral gene constructs. Among the numerous transgenic crops produced and evaluated in the field, papaya resistant to Papaya ringspot virus (PRSV) [Annu. Rev. Phytopathol. 36 (1998) 415] and summer squash resistant to Cucumber mosaic virus (CMV), Zucchini yellow mosaic virus, and/or Watermelon mosaic virus [Biotechnology 13 (1995) 1458] were released for commercial use in the USA. Although cultivated on limited areas, the adoption rate of cultivars derived from these two crops is increasing steadily. Tomato and sweet pepper resistant to CMV and papaya resistant to PRSV were also released in the People's Republic of China. Applying the concept of PDR provides unique opportunities for developing virus-resistant crops and implementing efficient and environmentally sound management approaches to mitigate the impact of virus diseases. Based on the tremendous progress made during the past quarter century, the prospects of further advancing this innovative technology for practical control of virus diseases are very promising.