Confined Production Processes for Non-Food Corn - Seed Science ...

target field in inverse proportion. For most hazardoussubstances, risk is proportionate to concentration and isbe lowered as the concentration is lowered. If a PMP orPMI is associated with hazard, covering tassels, keepingthe ratio of transgenic to nontransgenic plants low, limitingthe number of PMP and PMI plants, or the use of malefertile nontransgenic borders that reduces the concentrationof PMP and PMI pollen at the source, all could reducethe risk associated with undetected escapes.Possible differences between the nursery and large-plotprocedures could reflect the relatively smaller amountof PMP- or PMI-pollinated material from borders thatwould have to be destroyed. Current APHIS standardsexplicitly preclude borders that are managed externalto the field trial, so as to avoid potential loss oftransgenic material from confinement through impropermanagement of that potential PMP or PMI materialthat may occur in borders separated procedurally fromthe contents of the trial. In practice, within field trialsthere are frequently plants that are neither PMP nor PMIand are allowed to open pollinate. These plants contributeto the reduction in concentration of PMP or PMI pollenin outflows. The nontransgenic male plants occurring onthe field trial periphery have the benefits of borders.These designs seem appropriate under APHIS conditions,because all materials within the field trial are managed asif transgenic.Misidentification and unintended intercrossing is aconcern in nurseries containing many regulated traits.This concern is similar to that discussed in greenhousework. Because the plants are handled in systems withwell defined record keeping and identification, such risksare minimized. Separation of transgenic nurseries withregulated events from nurseries with no regulatedevents allows for checks for unintentional crosses andmisidentification prior to the release of inbreds for largerscale trials. These checks can be made with event-specificPCR probes. Before the release of breeder’s seed, theidentity of events should be rigorously determined withevent-specific PCR tests. Event-specific PCR also can beused to test the component lines used to maintain breederseed stocks.Unintended events from the nursery system for regulatedevents pose a special problem in nurseries with noregulated events. This can be avoided by providingextra isolation of nurseries with regulated events fromnurseries with no transgenes or transgenes that havebeen deregulated and approved for food and feed use.Various levels of size, isolation, borders, and pollencontrol can be combined to achieve a given goal for cornpollen confinement. Control of the concentration ofPMP and PMI pollen at the source can be used to reduceany risk associated with escape from a hazardous PMPor PMI source. We design our model to reflect theseprocedural options.When BIGMAP results are used for policy discussions, itmay be possible to consider regulatory changes. For traitsof hazards known to be below some level, combinationsof the above-mentioned procedures may allow considerationof isolation distances less than 1 mi (