Bt Brinjal The scope and adequacy of the GEAC environmental risk assessment

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44 Bt Brinjal: The GEAC environmental risk assessmentIn some areas of India brinjal is cultivated once a year during the rainy season, and BFSB can complete up to threegenerations. In other regions brinjal is cultivated throughout the year, and BFSB can complete 8 or more generations.We assume that wherever brinjal is grown, Bt brinjal will be grown during only one time of the year, so that only threegenerations of BFSB will be exposed to Bt brinjal a year. This is probably satisfactory for those regions with singlecropping. For regions where brinjal is grown throughout the year, Bt brinjal could be grown during two or more seasons.In these cases, the time to resistance failure would be projected to occur much sooner. If two crops are grown resistancefailure would occur twice as fast, and if three crops are grown, it would occur three times as fast as what we project here.i. Based on the results from the small-scale field trials (Dossier, volume 6) and the published literature (Caprio et al. 2000,Meihls et al. 2008, Anilkumar et al. 2008) on other low dose Bt events, we suggest that when resistance is found in BFSB,that it will be partially recessive with heterozygosity (h) between 0.2 and 0.4.j. We also assume that there is strong density dependent population growth. This is because larvae are forced to interactin brinjal fruits. This results in a = 6 and b = 0.8. the stronger the density dependence the longer the time to resistancefailure. However, this effect is minor except in some special cases.k. We assume that per capita fecundity (F) is 100 offspring per female. Although most moths can produce several hundredeggs, this value is used because it counts only one of the two sexes (the females), and includes egg mortality and otherforms of density-independent mortality.l. Finally, we assume that the frequency of resistance alleles ( p 0) in the natural BFSB populations is low, less than one in10,000. This value is lower than most observed initial R allele frequencies for Bt resistance. Time to resistance failure islonger for lower values of initial resistance frequency.Using these assumptions, we can simulate evolution for two levels of adoption of Bt brinjal (50% adoption and 90%adoption), the two values of heterozygosity, and several refuge assumptions. Adoption rate is not for the entire country. Becauseevolution will occur locally, adoption is probably related to the district level within states, and possibly at finer spatial scales. Ingeneral, heterozygosity has large effects on resistance evolution, so we simulated the extreme values that are expected for BFSBand EE-1 Bt brinjal. We simulated no refuge (or 0% compliance), and 5, 10, and 20% non-Bt refuge with 100% compliance.Intermediate levels of compliance will produce results intermediate between 0% refuge and the recommended % refuge.The simulations show that resistance is projected to occur rapidly, sometime between 4 and 17 years (Fig. 2). The precise valuescan be disputed, but a robust conclusion is that under some conditions, resistance failures can occur rapidly (less than 4 years),and under other conditions, it may take many years for resistance failures to show up. Thus, efforts should be taken to ensurethat India is more likely to experience the latter conditions than the former conditions.This could be difficult. Local adoption rate has the largest effect on resistance evolution (Fig. 2). If adoption stays below50% and heterozygosity is closer to 0.2 than 0.4, then Bt brinjal may last for many years. However, if Bt brinjal is truly aseconomically beneficial as projected in EEII and the Dossier, local adoption rates are likely to be much higher than 50%,and the resistance risk is very high. The resistance risk is greatest where adoption is highest, so India should pay attention toadoption rate if Bt brinjal is commercialised.The level of heterozygosity has a large effect on the rate of resistance evolution.Unfortunately, it is not possible to know the value for heterozygosity until aresistance allele is discovered in BFSB. Thus, it should be a high researchpriority to discover resistance alleles to EE-1 Bt brinjal in BFSB (see below).A 5% refuge has little effect on the rate of resistance evolution (Fig. 2). If there is a cost to resistance a 5% refuge will have alarger effect at delaying evolution, but this is still likely to be small quantitatively. A larger percent refuge will be better at slowingresistance evolution. A 20% refuge will increase the time to resistance failure by 25% (Fig. 2). If there is a cost to resistance, theefficacy of the refuge in delaying resistance is likely to increase substantially. If India is going to manage resistance a refuge largerthan 5% seems necessary.The assumptions that we have made in these simulations are not worst-case assumptions. Indeed, BFSB may be exposed
Environmental Risk Assessment 45to selection more than 3 generations a year, heterozygosity may be higher than 0.4, and the initial frequency of resistancealleles may be higher than 0.0001. If any of these were true, Bt brinjal would fail even faster. On worst case assumption is thelack of a cost of resistance. If an efficacious refuge were used, the cost of resistance could extend the time to resistance failuresubstantially. These projections can be improved by estimating the values of some of the key parameters. Given the possibilityof rapid failure, many of these experiments should be conducted prior to commercialisation.Finding 22. Resistance monitoring in BFSB should begin as soon as possible, especially in the peri-urban large-scalecommercial production regions, and should expand to include rural areas at risk.Because Bt brinjal is projected to fail quickly unless resistance is managed, it is essential that the frequency of resistance inBFSB populations is monitored to enable the government, industry and farmers to respond to the increased risk of resistancefailures. The presently proposed monitoring plan (elements A, B and C above) will not provide information on the frequencyof resistance. They are designed to monitor for control failures due to resistance. Monitoring the frequency of resistance willprovide an early warning, so that farmers are not subjected to yield failures associated with control failures. Monitoring forcontrol failures will result in some farmers losing brinjal yield without warning. The social good is better served by monitoringfor the frequency of resistance.This does not deny that there are advantages to monitoring for control failure. For any technology, including agriculturaltechnologies, it is useful to be able to know when the technology no longer works as expected. This is what monitoring forcontrol failures accomplishes. This information has little present value for farmers, because by the time the information isavailable, control failures have occurred. It can help them choose appropriate brinjal varieties for planting in the future. Theinformation may be of use to government, which can modify policies related to GM crops based on the information. Theinformation is useful to the technology providers, in this case Mahyco, because they can adjust their future sales, varietydevelopment programs, and educational materials to farmers in ways to retain their share of the brinjal seed market.There are many monitoring methods available, but pedigreed screens (Andow and Bentur 2010), such as F 2and F 1screens,are widely used and are probably appropriate to the BFSB. The only technical concern in using pedigreed screens is thatindividual pedigrees can be distinguished and maintained during testing. Because resistance is assumed to be only partiallyrecessive and possibly almost co-dominant (h = 0.2 or 0.4), phenotypic screens may be the most cost-effective. A pedigreed F 1screen differs subtlety, but in extremely important ways, from the proposed F 1screen (element B above). A pedigreed F 1screenmaintains the identity of the parents for each F 1offspring tested, while the proposed F 1screen combines all of the offspringprior to testing. If offspring are combined, it is no longer possible to know how many parents had offspring or how manyparents carried resistance alleles. In addition, random sampling breaks down, because some parents contribute more offspringthan others. A pedigreed F 1screen should be required for monitoring. Of course, if resistance is found to be nearly completelyrecessive, then even this approach will not work, and an F 2screen would be more cost-effective.Locations that are monitored should be distributed over the geographic range where Bt brinjal is used, but efforts shouldbe concentrated in locations with the highest use of Bt brinjal. The Indian government should track the use of Bt brinjal toidentify the locations where it is used most commonly. There are no data that indicate the spatial scale over which locationsshould be sampled. As a first approximation, Bt brinjal use should be tracked at the District level, but it is likely that smallerareas than this may require monitoring. The peri-urban, large-scale commercial growers may be the initial users of Bt brinjal, sosome monitoring should be initiated in these areas as soon as possible.Needed Experiments and ObservationsSeveral rather significant issues need to be addressed. Points 3, 4, 5, and 7 can be delayed until early during commercial use,but if they are delayed, then IRM must be based on worst-case assumptions, and the registrant should be granted a conditionalregistration that will automatically expire unless they provide the information by a specified date.1) Develop resistance monitoring method. Develop and implement a pedigreed F 1screen. This should not take undueeffort, but the method should be verified, repeating much of the work that has already been reported for baseline susceptibilityusing a discriminating dose, such as Bt brinjal plant material in laboratory assays. By doing so, a more accurate and meaningful
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Page 9 and 10: Summary and Conclusion 5Event EE-1
Page 11 and 12: Summary and Conclusion 7Conclusion
Page 13 and 14: Context and Need 9standards for ER
Page 15 and 16: Context and Need 11and seek to incr
Page 17 and 18: Context and Need 13the reported yie
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Page 23 and 24: Characterisation of Transgene 19In
Page 25 and 26: Characterisation of Transgene 21Sci
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Bt Brinjal The scope and adequacy of the GEAC environmental risk assessment

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