are also mentioned, such as leaf striping on transgenic plants as compared to nontransgenic plants in Puerto Rican field trials and more predictable but secondary effects, such as reduction of stalk rot in transgenic plants.
In contrast to the document for CBH-351, the APHIS determination for Event 176 did not mention or evaluate descriptions of the event regarding pleiotropic effects or other unpredictable consequences of the random insertion of these genetic sequences, the number of copies, and stability of the transgenes. The determination for CBH-351 was more detailed than was the earlier determination, suggesting either that APHIS received more information, adjusted its evaluation procedures, reported more details in its summary, or some combination of the three.
Weediness of the Crop Plant Resulting from the Transgene and Associ ated Gene Sequences. For both Event 176 and Event CBH-351, APHIS addressed the risk that expression of the insect control protein might provide a selective advantage to the plant, sufficient to make it a plant pest. For Event 176, APHIS first compared the characteristics of nontransgenic cultivated corn with a list of ideal characteristics of weeds published by Baker (1965) and found little overlap. Though noting that some ecologists have criticized this list, APHIS relied on it anyway because no more broadly accepted suite of characteristics was available. Second, APHIS assessed the weed status of corn, consulting several weed compendia and found that corn was not listed in most of them. Third, APHIS considered the trait itself—insect resistance. APHIS concluded that since insect resistance was not among the weedy characteristics listed by Baker, that trait would not likely contribute to weediness in transgenic Bt corn. The herbicide tolerance trait of Event 176 was not perceived as one that could reverse the plant’s nonweed status, primarily because glufosinate had not yet been registered for use in corn. Finally, “APHIS evaluated field data submitted by Ciba Seeds which specifically demonstrates that Event 176 corn is no more weedy than the non-modified recipient.” These field data were not available to this committee, so it cannot comment on the adequacy of the study in supporting that conclusion.
APHIS used the same arguments for the later determination (USDA 1998) for Event CBH-351, citing Baker (1965), and noting that insect resistance was not listed as a characteristic of weeds. APHIS also found no differences between CBH-351 and its nontransgenic counterpart or a nontransgenic standard line in field tests conducted from 1995 to 1997 in 17 states and territories of the United States in Bt corn’s ability to compete or persist as a weed. The CBH-351 determination pointed out that other corn genotypes with resistance to certain Lepidopteran pests, including ECB, have been in use for decades and have not been reported to cause increased weediness. Given these data and observations, APHIS concluded