Although currently there are no standards in the United States to separate government-approved biotechnology traits, 1 percent adventitious presence has been suggested as the standard for adventitious presence of biotechnology-derived traits in non-transgenic varieties of seed crops in export markets. Handling of RR alfalfa seed may also require additional checks in place to prevent co-mixing of transgenic and conventional seed, depending on the market destination of the seed. For a review of crop identity preservation, see Sundstrom et al. 2002.Hundreds of alfalfa varieties have been developed for use in North America using conventional breeding methods of crossing and selection. These varieties are adapted to the major alfalfa production zones and contain important genes for high yield, resistance to diseases, insects, and nematodes. Growers have been the beneficiary of decades of plant breeding by public institutions and private companies and competition between seed companies for their business. Several alfalfa seed companies will likely be marketing RR alfalfa varieties to satisfy a range of market conditions. Although Forage Genetics International has developed the initial RR alfalfa cultivars, other alfalfa breeding companies will have access to the trait. Fall dormancy is a major criterion for variety selection. In the first few years of release of the RR technology, the selection of varieties is likely to be limited to varieties within a small range of fall dormancies, vertical farming systems for sale with other fall dormancy classes to follow in subsequent years.
With the introduction of the RR trait, variety selection will include consideration of yet more “value-added” traits that should be considered in addition to yield and other traits. Generally, the protocol for selection of RR lines does not differ significantly from the selection of conventional lines. Fall dormancy group, yield potential, disease and insect resistance, and forage quality should all be considered, in addition to the value of the herbicide resistance. Calculations of potential benefits from the weed control technology should be compared to the added cost of the seed, relative costs of herbicide strategies, and potential limitations of the technology.Recommendations for seeding rates vary significantly across the United States. California currently recommends a range of 15 to 25 pounds per acre of seed, depending on seeding method and soil preparation. Although the price of seed is typically less than 2 percent of the total cost of production for growers, as the value and cost of seed increases, the relative economic impact of seeding rates and method increases. Precise seeding methods combined with proper soil preparation allow good control of seeding depth, seed placement, and soil-seed contact. Irrigation and early weed control during stand establishment reduce the probability of stand failure. These practices may enable growers to lower seeding rates, and thus manage cost of seed for higher-value genetics.Enhancing Weed Control Options Current technology controls most but not all weeds. Certain weeds, such as Canada thistle , dandelion , dodder, nutsedge, bermudagrass, , and quackgrass are particularly problematic. Annual weeds such as barnyardgrass , pigweed, lambsquarters, foxtails , nightshades, downy brome , and mustards can be troublesome at certain times. A subset of these weeds can be controlled by a combination of currently available herbicides in tank mixes or multiple applications, but Roundup controls a broader weed spectrum and may be more efficacious than most currently available herbicides or herbicide combinations .
Weed Control Flexibility While many available weed control options have fairly well-defined requirements and restrictions as to application timing, temperatures, and environmental influences, Roundup strategies are likely to provide a more-flexible option to growers. Although timing with Roundup applications is to some degree still important, it may not prove as important as it is with some of the alternative methods. The high degree of flexibility and broad-spectrum weed control are the principal benefits of RR alfalfa. Potential Economic Benefits Roundup Ready technology has the potential to provide more-reliable stand establishment and improve alfalfa yields and forage quality due to reduced weed contaminants. The value of alfalfa per ton may be improved, since pure alfalfa is usually worth 20 to 50 percent more than weedy hay. Other possible benefits include extended life of stands and improved crop safety compared to other weed control options. However, as of this writing, the economic benefits of the RR technology are not entirely clear, since the pricing structure has not yet been determined. Animal Feed Safety and Animal Health Contamination with poisonous, antinutritional, or simply unpalatable weed species is a common hazard of livestock feeding. Veterinary diagnostic labs and veterinarians each year report many cases of horses, cows, and sheep that are killed or sickened after consuming alfalfa that has been contaminated with such weeds. Some weeds simply lower animal performance or milk production, but others can kill. Roundup Ready alfalfa provides a simple option to minimize the risk of consumption of poisonous or unpalatable weeds by livestock, and it has the potential to improve animal welfare and production by increasing the feeding of pure, weed-free, high-quality alfalfa hay. Water Quality In addition to the benefits in terms of crop productivity, crop quality, animal production, and value, RR technology may replace some herbicides that have the potential to contaminate water supplies. Several herbicides used in alfalfa during the winter period have been detected in wells in California’s San Joaquin Valley . To the extent that it replaces those options, RR technology could lessen this environmental concern, since there is little evidence of off-site environmental impacts from glyphosate . Preventing Spread of Noxious Weeds Although all successful weed control strategies share this characteristic, RR alfalfa could improve the ability of growers to slow or stop the spread of noxious weeds in hay. The U.S. Forest Service and other agencies have encouraged the use of certified weed-free hay to be brought into natural areas for livestock and pack horses to prevent the spread of noxious weeds into environmentally sensitive areas. Roundup Ready technology could aid in that effort by creating “weed-free” alfalfa hay.Weed Control Limitations Although the spectrum of weeds controlled by Roundup is impressive, certain weeds are not completely controlled by Roundup. These include cheese weed , burning nettle , filaree , and others. In addition, Roundup has no residual activity that controls weeds for longer periods, as some conventional herbicides do. Roundup Ready technology should not be viewed as a panacea, vertical farming equipment but as a component of an overall weed control effort on a farm. Weed control strategies that incorporate cultural methods and rotation of herbicides will be needed to combat weeds not completely controlled by Roundup in order to prevent weed shifts. Herbicide Resistance One environmental concern about RR technology is the development of herbicide resistance in weed populations. This becomes more of a concern as the acre treated with Roundup increases. Since RR technology already encompasses many crops , it is very likely that tens of millions of acres will be treated with Roundup each year nationally.
Evidence for Roundup resistance has already been identified in natural populations in some species, such as ryegrass and horse weed . It is possible that this might occur in other species. This problem is not unique to Roundup but is common for other classes of herbicides as well. The development of weeds with resistance to Roundup is thought to be less likely than for other herbicides, as Roundup has no soil residual activity, and Roundup has a unique mode of action. Herbicide strategies that incorporate integrated cultural methods and rotations of herbicides are needed to prevent herbicide resistance. This is especially important to control volunteers of subsequent herbicide resistant crops. Weed Shift A weed shift is a change in the relative frequency of weeds in a population in response to a management practice. In the case of herbicides, weed shifts occur when a herbicide does not kill the entire weed spectrum encountered in a field. The density of the weed species that is not controlled increases over time, resulting in a weed shift. While Roundup is perhaps the most broad-spectrum foliar herbicide available, it is not equally effective on all weeds. Roundup is less effective for the control of many common weeds, such as cheese weed, burning nettle, filaree, and purslane. Over time, if Roundup is used repeatedly as the only weed control measure, the prevalence of these weeds is likely to increase. This has already been observed in a trial in San Joaquin County, where burning nettle was not adequately controlled with Roundup , and the population of this weed has increased significantly over a 3-year period. As with herbicide resistance, the best practice to prevent weed shifts is to avoid using the same herbicide year after year and to rotate herbicides and crops, as well as using non-herbicide strategies to control weeds. Gene Flow to the Environment As the RR gene is new to alfalfa, its effect on the environment must be studied in the context of gene movement and persistence in plants. Genes introduced through biotechnology are passed on from generation to generation and to and from close relatives as any other gene in plants. It is important to establish strict management protocols to ensure varietal purity and minimize gene flow to and from unwanted sources, also known as adventitious presence. Gene flow is affected by sexual compatibility, flower characteristics, pollen viability and quantity, proximity of neighboring plants, pollinator activity, and environmental conditions. In the United States, there are no sexually compatible wild relatives to alfalfa; feral alfalfa is the only plant it can successfully cross with.The potential environmental impact of the gene flow from RR alfalfa to feral alfalfa must be understood in terms of “fitness.” Alfalfa generally is not considered by weed scientists to be an invasive weed, but it does occur along roadside ditches and in agricultural areas. If the RR gene is transferred to feral alfalfa, it is not clear that these plants would have any natural advantage over conventional alfalfa, or any greater weedy characteristics, except where Roundup is sprayed. Research is currently being conducted by University of California scientists to determine the proper weed management programs to prevent outcrossing and to control feral alfalfa. As our alfalfa removal studies have shown, several commercial herbicides are currently available for removal of RR alfalfa. For the 22 million acres of alfalfa in the United States, the issue of crossing RR alfalfa with feral relatives may not be a major issue, since these fields are typically harvested in the prebud to midflower stage of development, thus little pollen flows and few viable seeds are set . The issue of gene flow is primarily a concern in seed production, where pollen flow is necessary for seed set. Currently, less than 0.5 percent of the alfalfa grown in the United States is grown for seed. Market Acceptance of Roundup Ready Hay Roundup Ready alfalfa will be the first genetically enhanced alfalfa product to be marketed commercially. It is anticipated that the first commercial crops will be grown in 2005. In most parts of North America, the majority of alfalfa is fed on-farm, but in the western United States, the majority of hay is offered for sale to dairy, with the remainder to horse, beef, and export customers. Nationwide, most alfalfa is consumed by the U.S. dairy industry, where it is considered the premier forage crop. For example, in California, dairy cows consume greater than 75 percent of the state’s alfalfa crop. Thus, consumer acceptance of RR hay is highly dependent upon the acceptance of the dairy industry, which in the last decade has absorbed four to six new technologies related to genetically modified crops. Because of this, most experts believe that the dairy industry will, by and large, accept RR alfalfa. The horse industry may provide initial resistance, since individual preferences come to the forefront, but some buyers may be attracted to the “weed free” aspect of RR alfalfa. The organic market for hay is small and will likely reject RR alfalfa, as it does other biotech crops. Except for some specific markets such as organic, most alfalfa experts do not foresee significant market resistance to RR hay, with the exception of the export market. Exports The United States exports about 4 percent of its alfalfa to Japan, Korea, Taiwan, Mexico, and Canada. About 80 percent of U.S. alfalfa hay exports are destined for Japan , with approximately one-quarter shipped through California and three-quarters shipped through Oregon and Washington ports .