Alfalfa producers, for instance, maybe didn’t even have to think about it much, until genetically engineered (GE) varieties became available. Now, all of a sudden, the alfalfa industry is challenged to go beyond the theory of tolerance and make the practice work.
The issue is the detection of small amounts of GE hay in otherwise non-GE alfalfa, which has caused disruption in markets. China, one of the major buyers in the hay export business, recently decided to use a polymerase chain-reaction test (PCR) for GE alfalfa which is generally more sensitive than the lateral flow-strip tests that have been commonly used in the U.S. to detect GE presence in plant material. (Although it should be noted Envirologix recently reported sensitivity of test strips to 0.1 percent, which is the same as PCR.)
Subsequently, China has refused hay export shipments, which has hurt the U.S. export market. True to human form, whenever a large financial crisis threatens, as was the case here, the struggle for tolerance heightened and the key question became “How do these diverse systems co-exist?”
Dan Putnam, forage specialist at the University of California – Davis, says, “I would define co-existence as the successful ability for diverse systems – whether it’s organic, export … genetically engineered (GE) or non-GE – to thrive without undue influence of neighbors or resorting to extraordinary protection measures.” He adds, “Some people may differ about what extraordinary means, but this requires cooperation, mutual respect, as well as knowledge and some science. Also, it requires defined tolerances for the different kinds of markets.”
There are two influencing factors at play: technical elements and human issues. These factors, either in combination or stand-alone, are possible sources of low-level GE presence in hay lots.
Putnam described four possible sources for GE contamination within an alfalfa hay lot. These are described below by level of risk, with seed selection being the most important risk.
Traces transferred from seed at planting
The most likely culprit for low-level presence of a GE trait in alfalfa comes from the seed itself. Hay growers producing alfalfa for export must pay more attention to the purchase of non-GE alfalfa seed. Putnam says seed companies report less than 5 percent of growers are requesting non-GE or adventitious presence sensitive-certified (APS-certified) seed. This is a key limiting factor.
Growers can obtain non-GE seed, which has been tested from virtually any seed company, or can test it themselves. There are several sources of non-GE seed. Growers can purchase “non-detect” seed, a process that identifies GE alfalfa traits in seed at a rate of 0.1 percent or below with a 95 percent confidence level.
An additional source is APS-certified seed, a process initiated by the Association of Official Seed-Certifying Agencies (AOSCA) that requires additional isolation distances as well as testing. Putnam says seed tested with the non-detect protocol will likely produce non-detect hay through the crop’s lifetime.
Partial bales transferred during harvest
If balers move between fields, from a GE field to an otherwise non-GE field, partial bales still existing in the baler at the time of the move may be transferred to other fields. That one bale would likely be stored within the new field hay lot. Thus, a small amount of GE hay may occur within the entire lot.
Bale mix-up during handling or shipping
GE alfalfa can be inadvertently mixed after harvest. Human error can account for bales or entire stacks to be mislabeled or mixed during handling or shipping. This could be a potential source of low-level GE presence even though it may not be distributed evenly throughout the hay lot.
Gene flow
It is also possible that gene flow might occur between neighboring hay fields. Putnam says, “I feel this is actually one of the least risky aspects, even though [alfalfa] is a bee-pollinated crop. This is because the field practices largely limit gene flow between hay fields.”
Why? In order for a gene transfer to occur between neighboring alfalfa hay fields, a series of events would need to play out, including:
1. Fields need to be in close proximity.
2. There would need to be simultaneous flowering in neighboring fields.
3. Large numbers of pollinators must be present and active.
4. Flowers that were cross-pollinated would have to produce a viable embryo and seed, which normally takes 30 to 45 days past flowering.
5. Seed must mature.
6. The cross-pollinated seed would have to drop to the ground, germinate, grow and produce a plant.
7. Those plants would then contribute low-level presence to the hay crop.
How high is the probability of all events occurring? Due to frequent harvests and crop removal, Putnam says gene flow between hay fields would be generally less than 0.01 percent, or below the threshold of tolerance or measurement in hay for sensitive markets.
It’s not an impossibility, but is a very low risk due to frequent harvests and the lack of significant seed production in hay fields.
Sampling protocol
Sampling protocols to detect low-level presence (LLP) of GE alfalfa may result in endemic detection or random detection. Endemic contamination (or widely distributed GE throughout the lot, as the case with seed that is non-APS certified) can be detected through sampling.
However, a random or occasional effect (such as partial GE bales transferred at harvest to a non-GE field, which would affect only one bale) cannot be reliably tested through current sampling protocols.
While sampling for LLP of a GE trait is similar to sampling hay for forage quality, there are some differences. While forage quality testing seeks to determine the average characteristic of hay, the objective for GE sampling is to determine a specific small concentration of a gene or gene product.
Forage quality, for instance, will consider leaf-to-stem ratio or weed contamination, while this is not important for GE detection. In both cases, sampling must attempt to provide a subsample that truly represents the entire hay lot.
Putnam and his colleagues counted stems in hay sampling cores and found an average of 250 stems per core. Assuming each stem represented one plant, they reached an estimate of 30 probes needed per sample per lot in order to detect about 0.013 percent of the mass.
He concluded 30 probes per sample per lot would probably be adequate for a target of 0.1 percent or less GE product, which would equate the PCR analysis level.
Putnam emphasized that the protest strips commonly used in the U.S. are only adequate to about 1 to 5 percent of a low-level GE presence, whereas PCR (used by China) detects levels at about 0.1 percent or even below in some cases.
Putnam says essentially some governments have “zero” tolerance for GE crops, which is an “absolute impossibility.” In order to assure a hay lot “GE-free,” every last gram of the lot must be tested.
Further, a single stem present in a 200-ton hay lot would constitute low-level presence in a technical sense, while it is unlikely any sampling or analysis would successfully detect it.
Summary
GE crops are not going away, and there are other GE alfalfa traits currently in development. In order to foster co-existence now and in the future:
- Growers must specifically request APS or non-detect alfalfa seed.
- Balers must be completely empty when moving from field to field.
- Care must be taken to identify, store and label lots correctly.
- Growers need to control gene flow through distance and control of feral alfalfa, harvesting before excessive flowering and crop removal.
Alfalfa growers are not the only producers to scale this cliff of co-existence; sweet corn, field corn and sunflower crops are among GE crops that have co-existed with conventional varieties while maintaining genetic integrity.
Alfalfa producers, however, must adjust and refine current practices to foster co-existence in a divergent alfalfa industry. FG
Go to Video: Preparing hay for export to watch a video of hay being prepared for export.
Go to Protocol for genetically modified hay sampling to read an online-only article outlining sampling protocols for hay exports.
