Publications: ISAAA Briefs

No. 2 - 1997

Insect resistance in Crops:  A Case Study of Bacillus thuringiensis (Bt) and its transfer to Developing Countries

Anatole F. Krattiger
Executive Director of ISAAA


Published by: The International Service for the Acquisition of Agri-biotech Applications (ISAAA). Ithaca, New York 
Copyright: (1997) International Service for the Acquisition of Agri-biotech Applications (ISAAA) 
Reproduction of this publication for educational or other noncommercial purposes is authorized without prior permission from the copyright holder, provided the source is properly acknowledged.
Reproduction for resale or other commercial purposes is prohibited without the prior written permission from the copyright holder.
Correct Citation: Krattiger, A.F. 1997. Insect Resistance in Crops: A Case Study of Bacillus thuringiensis (Bt) and its Transfer to Developing Countries. ISAAA Briefs No. 2. ISAAA: Ithaca, NY. pp. 42.
Cover Picture: Left:  The diamondback moth prefers wildtype broccoli; 
Right:  Bt-transformed broccoli is resistant to diamondback moth. 
Courtesy: T.D. Metz and E.D. Earle (Cornell University). 
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Executive Summary
List of Tables and Figures

1. Introduction
2. Overview of Insect Resistance Mechanisms in Crops
3. From Bt Biopesticides to Transgenic Crops

    3.1 Bt and Biopesticides
    3.2 Bt Patents and Insect Resistant Crops
    3.3 Bt Endotoxins and their Genes
    3.4 Case Study on the Development of Bt Transgenic Cotton

4. The Potential of Bt Transgenic Crops to Substitute for Traditional Insecticide Use

    4.1 Crop Losses due to Insects
    4.2 Potential Substitution Value
    4.3 Current Licensing Costs of Bt Technology

5. Current Status of Field Trials with, and Commercialization of Bt Crops
6. Management Strategies of Bt Deployment

    6.1 Overview and Introduction
    6.2 Refugia and Mixtures
    6.3 High Dose and Low Dose Approaches
    6.4 Multiple Gene Deployment
    6.5 Targeted Expression
    6.6 Subsection Conclusions

7. Issues Related to the Transfer of Bt Technology

    7.1 Introduction
    7.2 Research and Development Capacity
    7.3 Regulatory Issues (Biosafety and Food Safety)
    7.4 Intellectual Property Rights (IPRs) and Licensing Issues

8. Conclusions and the Future of Insect Resistant Crops in Developing Countries


    I:  List of Latin Names for Cited Insect Species
    II: List of Major Research Centers Working on Various Aspects of Bt
    III:  Nomenclatures of Bt Endotoxins (Genes)

Executive Summary

Despite significant increases in per capita agricultural production worldwide over the last decades, the challenge of producing sufficient food supply remains daunting given increasing population growth, reduced availability of water, and limits to agricultural land expansion. Biotechnology applications, if properly integrated into production systems, offer new opportunities to increase production and productivity by using a more sustainable and ecologically friendly agricultural system.

One such near-term biotechnology application is insect resistant crops through the insertion of a gene from Bacillus thuringiensis (Bt) that produces a protein toxic to certain insects (of Lepidoptera, Coleoptera and Diptera families). A review of the known genes, as well as an outlook on the next wave of insect resistance technology (e.g. smart proteins, VIPs), reveals that Bt is merely the beginning of a long series of new and safer technologies to augment productivity, to bring about a more sustainable agriculture, and to protect the environment. With Bt alone, there are already over 50 genes with known insecticidal properties. Several of these could be deployed simultaneously (provided they have different modes of action) to increase the level of protection of the crop and possibly reduce the risk of insect populations developing resistance. So far, the efficacy of insect resistant crops through Bt has been shown to be comparable to or better than the efficacy of current control methods. One reason is that fewer insecticide applications are required and in some cases a Bt crop may not require any insecticide sprays at all. Fewer applications save cost and time, in addition to reducing health risks to workers (a particularly hazardous activity in many developing countries). Ecological benefits should not be underestimated either, since the Bt toxins are highly specific against certain insects without affecting predators and other beneficial insects. This is not the case for many insecticides, such as the broad-spectrum pyrethroids.

Bt has been used for a long time as an effective biopesticide in agriculture, yet it represents less than 1% of insecticides used on a global basis. The market of insecticides is US$8.11 billion annually, with 30% of them applied on fruits and vegetables, 23% on cotton and 15% on rice. Asia produces 92% of the world production in rice and nearly US$1 billion is spent on insecticides for that crop in Asia alone. In cotton, more insecticides are applied than in any other crop (US$ 1.9 billion annually). Yet around US$1.2 billion in insecticides on cotton could be substituted with Bt biotechnology applications. The development of Bt cotton is presented and discussed as a detailed case study on transgenics. In rice, approximately US$400 million is spent on insecticides against the rice stemborer, which could completely be substituted with Bt transgenic crops. The total insecticide substitution value for the major crops of cotton, maize, rice, fruit and vegetables is estimated at US$2.69 billion annually.

A review of field trials of transgenic Bt crops shows that the first trials took place as early as 1986, but large scale trials were only numerous in OECD countries since the early 1990s. As a consequence, several million acres of Bt crops have been planted in the USA in 1996 (cotton, corn/maize, potatoes) and this is expected to increase substantially in 1997, and will include several European countries, Argentina, South Africa and Australia. Few developing countries are near commercialization of the technology which is also reflected by the fact that developing countries conducted less than 3% of the Bt field trials worldwide with few having effective biosafety regulatory mechanisms in place. A priority issue for developing countries will be how to gain access to this technology and develop effective and safe deployment strategies.

All commercialized Bt crops are by the private sector which is not surprising considering that 410 -Bt-related patents were issued over the last 11 years: just over half of Bt related patents were granted to institutions in North America, 30% to European and Russian organizations, and 18% to companies mainly from Japan; of the total patents, over half are directly relevant to transgenics; and fifty-seven percent of all Bt patents have been issued to only eight companies. An analysis of commercialized Bt crops and of recent field trials demonstrates that a subset of these eight corporations are the major players in transgenic Bt plant technology, viz. Monsanto, Novartis, AgrEvo and Mycogen with their own technologies, and DeKalb Genetics Corporation and Pioneer Hi-Bred International through strategic alliances. The most advanced products include cotton, corn/maize, potato, tomato, canola/rapeseed and tobacco, and approximately 20 corporations are advancing their own products. This large number of companies working on Bt (partly under license) demonstrates that the few major players who own enabling technologies are willing to license despite the fact that 23 lawsuits on Bt are pending. These are not restricting the technology from being commercialized, but will determine who receives the largest portion of royalties.

Bt crops—if deployed responsibly—offer substantial benefits and have the potential for significant short-term impact. Long-term impact can only be sustained if effective and responsible deployment strategies are adopted to maintain the durability of the Bt genes. Such deployment strategies must be aimed at reducing the possibility of long-term impact by preventing resistant insects from mating with other resistant insects, thereby preventing the creation of a resistant population. But the strategies must also be designed to be effective in the event that insect resistance does develop.

Several strategies are presented and discussed (gene strategies, gene promoter, gene expression, field tactics), and a review of adopted procedures shows that a high dose approach (high gene expression) with separate refuge areas has been most widely adopted so far. The strategy still requires the monitoring of fields for early identification of possible resistant insects. This poses formidable challenges because collecting insects at random may not necessarily allow early enough detection of resistance to allow remedial actions to be implemented. Requesting farmers to monitor insect damage to crops has limitations, particularly in developing countries and small-scale agriculture where the extension efforts required for such a system to work are tremendous. This section concludes that the effect of the adopted strategies is still somewhat speculative. Unfortunately, only large-scale deployment will provide the true test for the durability of the genes and the generation of a body of evidence that will allow optimum and safe deployment strategies to be developed.

Finally, critical issues related to the transfer of the technology (e.g. biosafety regulatory obstacles, intellectual property rights and licensing issues) are discussed, with particular reference to their implications for the developing countries. The delivery of new technologies to developing countries, many of which do not have a fully developed private sector seed industry has always been more challenging. With biotechnology applications, some of the constraints imposed by traditional technologies do not apply (for example, biotechnology applications, as opposed to mechanization, is essentially scale-neutral). However, insect resistance with Bt presents a particular challenge due to the requirements for managing the deployment of the technology in terms of avoiding insect resistance.

It is concluded that the recent developments in biotechnology demonstrate that Bt is merely the beginning of a long series of new and safer technologies to augment productivity, to bring about a more sustainable agriculture, and to protect the environment. With the emergence of an increasingly broad range of possibilities from the point of view of the technology, emphasis must now be placed on the development of transfer and delivery mechanisms to the resource poor farmers who are most dependent on novel solutions for their very livelihood and survival.

List of Tables

Table 1 Complementary Systems of Insect Resistance in Crops
Table 2 List of Institutions Holding Two or More Bt-Related Patents
Table 3 List of Major Corporations Developing Transgenic Crops with Bt Genes
Table 4 Bt Endotoxins (Cry) and their Activity against Specific Insect Species
Table 5 Global Losses due to Diseases and Insect Pests
Table 6 Global Production of Major Crops
Table 7 Global Value of Current Annual Insect Control Costs and Potential to Substitute with Bt Technology for Selected Major Crops and Insects
Table 8 The first Bt Field Trials with Transgenic Crops
Table 9 Commercialization Status of Bt Transgenic Crops
Table 10 Tactics Available for the Deployment of Insect Resistance Genes in Plants
Table 11 Complementary Bt Deployment Strategies
Table 12 Minimum Refuge Areas for Different Transgenic Crops to Prevent the Likelihood of Insect Resistance 

List of Figures

Figure 1 Cooperative R&D Agreements compared with Lawsuits involving Patent Right Infringements
Figure 2 Amino Acid Sequence Similarity of the Bt Endotoxins
Figure 3 1994 Worldwide Insecticide Use on Major Crops