Corn, in addition to being the most widely grown crop in the United States, is the most frequently targeted crop for improvements through genetic engineering. Fortunately, much is known about the biology of this crop, and the high degree of familiarity is helpful in risk assessments. In developing crop data requirements, APHIS considers the biology of the crop, interactions with the environment, and the nature of the inserted gene. In the case of corn, key biological features of the plant are that it has no sexually compatible relatives in the United States, it does not tend toward weediness, and it is wind pollinated. The nature of the inserted gene is also considered. Some data requirements may be specific according to the function of the gene. Other data requirements are more general and are aimed at whether the engineered crop has unanticipated effects that would render it phenotypically different from a near isogenic control.
For corn, the following list comprises factors which would be appropriate for inclusion in a data package and that would support a decision that the engineered plant was unchanged from a near isogenic control except for the desired change.
While objective, numerical data are most desirable, APHIS recognizes that not all parameters easily lend themselves to these types of measurements. In some cases data may be taken using subjective ratings using a descriptive scale. In other cases, data may be purely observational. What is required in all cases is that the methodologies are described in detail, such that the reader has an accurate understanding of the nature of the data and number of data points which make up a study and on which conclusions are drawn and the methods for analyzing the data. For example, is the unit on which data is taken a leaf, a plant, a row, or some other unit? Describe the total number of observations by describing numbers of replicate samples, rows, replicate blocks, locations, etc.
The above data should be collected on enough sites to adequately represent the major growing regions targeted by the product. The sites should also be selected in a way to ensure exposure to a reasonably wide range of environmental conditions. For corn with common agronomic traits or previously deregulated traits, APHIS recommends a minimum of eight sites be selected to represent the major growing regions in the U.S. Data from the eight sites may be collected in one or more years. When field-testing corn with less familiar traits or for traits where there is a reason to expect plant pest effects, more sites should be considered.
Last Modified: March 22, 2013