Because APHIS did not see a need for conducting an environmental assessment before approving this introduction, there was no opportunity for public or external scientific involvement in this permit decision.
Virus-based diseases can sometimes pose important problems for crop production (Hadidi et al. 1998). Virus resistance may be transferred into a crop via conventional breeding methods but only if that resistance already exists in the crop or in a sexually compatible relative. Transgenic virus resistance provides an opportunity for disease resistance in crops whose close relatives are not resistant to the virus in question. Transgenic virus resistance can be obtained by introduction of part of the disease viral genome into the susceptible plant genome; in particular, expression of the viral coat protein (CP) often confers resistance (Powell-Abel et al. 1986, Grumet 1995).
Field trials of dozens of crop species with transgenic-based virus resistance have been conducted (see “Field Test Releases in the U.S.,” Information Systems for Biotechnology online database: www.nbiap.vt.edu). As of April 2001, APHIS had approved six petitions for the deregulation of transgenic crops with virus resistance (see “Current Status of Petitions,” APHIS website: www.aphis.usda.gov/biotech/petday.html). The deregulated crops transformed are papaya, potato, and squash. The case of deregulation of Upjohn/Asgrow’s virus-resistant crookneck squash varieties (application numbers 92-204-01p and 95-352-01p) exemplifies how APHIS evaluated a number of different issues associated with the biosafety of a transgenic product.
Viral diseases are periodically an important problem for growers of squashes and other cucurbit crops (Desbiez and Lecoq 1997). These diseases include those caused by zucchini yellow mosaic virus (ZYMV), watermelon mosaic virus 2 (WMV2), and cucumber mosaic virus (CMV). Aphids act as the vectors of all three viruses.
Interestingly, squash varieties with genetically based virus resistance to WMV2 and ZYMV were developed almost simultaneously by both transgenic and conventional methods. In the same year, 1994, Harris Moran released a conventionally bred virus-resistant zucchini (Tigress)