The development of Bt eggplant represents a successful collaboration of the public and private sector to address a serious food security and production issue in Asia. The rapid adoption of Bt eggplant in Bangladesh reveals the significant economic and health benefits to farmers while reducing pesticides and positively impacting the environment.
Enhancing food and nutritional security while protecting the health of farmers and the environment.
Eggplant farmers in South Asia confront a menacing insect pest. Larvae of the eggplant fruit and short borer (EFSB), Leucinodes orbonalis Guenée burrow into the petiole and midrib of leaves and tender shoots resulting in wilting and desiccation of stems. The chronic and widespread infestation of EFSB is the biggest constraint to eggplant production throughout Asia. EFSB causes serious economic damage by producing holes, feeding tunnels and frass (or larval excrement) in the fruit, making it unmarketable and unfit for human consumption. Insect infestations cause up to 80% crop loss, which is devastating to the food security and livelihood for farmers across Asia.
To try and control the insect, farmers growing traditional eggplant varieties must spray harmful insecticides 2-3 times per week and up to 100 times per season, often without personal protective equipment. Such an insecticide-dependent strategy poses both environmental and health concerns. Environmental concerns include killing natural enemies that can help reduce pest populations, leaching into the soil and water, and harming pollinators such as bees. Health concerns include harm to the applicator and farm workers, as well as harm to the consumer from high pesticide residues on the crop. These problems have been documented in Bangladesh and the Philippines. This heavy insecticide usage is expensive, threatens the health of farmers and their families, and damages the environment.
A Scientific Solution
In the last few years, several crops have been genetically engineered to produce their own Bt proteins, making them resistant to specific groups of insects. Bt eggplant is genetically engineered to contain its own EFSB resistance mechanism − the Bt gene, cry1-Ac.
The cry1-Ac protein produced in Bt eggplant is similar in structure and activity to that found in nature and is already available and used commercially in the form of Bt-based biopesticide favored by organic growers. However, pesticidal sprays are only effective during the brief window before the larva hatches from the egg and bores into the fruit or shoot of the plant.
Once the larvae takes refuge within the fruit the insect is safe from surface sprays, however intensive they may be, and are free to destroy the crop from within. Bt eggplant, in which the cry1-Ac gene is genetically engineered into the plant, ensures a built-in resistance against the fruit and shoot borer larvae. When introduced into plants, the Bt gene produces proteins that are toxic to insects but harmless to humans and animals. The result: a safe, effective way to control a pest insect while protecting the health of farmers and the planet.
The Science Behind Bt Eggplant
Eggplant (brinjal) is a popular vegetable that provides an important source of income for small, resource-poor Bangladeshi farmers. The biggest constraint to brinjal production is the eggplant fruit and shoot borer (EFSB).
Eggplant, or brinjal (Solanum melongena), is a popularly consumed vegetable grown throughout Asia that is prone to vicious and sustained attack by the eggplant fruit and shoot borer (EFSB) (Leucinodes orbonalis) throughout the growing season.
The cultivation of genetically engineered crops has been expanded rapidly in worldwide in a very short span of time. Bt eggplant is a transgenic eggplant created by inserting a crystal protein gene Cry1Ac from the soil bacterium Bacillus thuringiensis.
Frequently Asked Questions
Bt eggplant has only been grown in a limited amount since 2014 so documentation on insecticide reductions is being developed but one report indicated a 74% reduction. Bt corn and Bt cotton have been grown since 1996 and the reduction in insecticide use has been dramatic with a 48% reduction in corn and a 26% reduction in cotton (Barfoot and Brookes 2014)
The cry1-Ac protein is highly specific to caterpillar pests and does not adversely affect non-target organisms, because they do not have the requisite receptor proteins found in the mid-gut of target insects. The vast data collected over many years of field trials conducted at various locations showed that non-target sucking pest counts did not vary significantly among Bt and non-Bt eggplant plants.
Field trial data demonstrate that Bt eggplant does not have any significant effect on soil micro flora (both fungi and bacteria), and soil invertebrates such as earthworm, collembola and nematodes. No cry1-Ac protein was detected in any of the soil samples from Bt eggplant field plots, which demonstrates that the protein is rapidly degraded. The cry1-Ac gene was derived from a common soil bacterium, therefore it is expected that soil micro-organisms are already routinely exposed to these proteins within the natural environment.
Bt eggplant has been developed by the Bangladesh Agricultural Research Institute (BARI) involving a consortium managed by Cornell University through the Agricultural Biotechnology Support Project II (ABSPII). The Maharashtra Hybrid Seeds Company Ltd. (Mahyco) donated eggplant Bt technology to BARI.
Many research institutions and activist groups have advised farmers to use less pesticides and chemical sprays for crops and go “organic”. How does Bt eggplant fit in with this idea?
There is no effective counter to pests such as the fruit and shoot borer in the organic cultivation of eggplant. Most available methods fall far short of effective goals at pest control. Bt eggplant, on the other hand, uses a gene from a naturally occurring soil bacterium to produce a protein that effectively combats the fruit and shoot borer, significantly reducing or even eliminating pesticide usage for this pest. This is a major step towards the stated goal of organic cultivation.
Is it true that Bt eggplant seeds are sterile after one harvest, forcing farmers to buy seeds for every planting?
Bt eggplant seeds are available as open-pollinated varieties in Bangladesh. Farmers can save seeds from their harvest for planting future generations, and indeed plant and grow the crop. For hybrids, as is the case currently for non-Bt eggplant (and indeed any hybrid cultivated crop), farmers must source fresh seeds year after year. This is because hybrid varieties do not breed true, so second-generation plants do not have hybrid advantages and are less useful for planting.
Bt eggplant seeds in Bangladesh are currently distributed for free. Seeds are made available to the farmers through the public sector seed distribution system. BARI is producing the seed of Bt eggplant in its seed production center.
Most insecticide sprays kill more than just the target pest and often kill beneficial insects, including pollinators, and other animals. Evidence from Bt crops grown in other countries has shown greater biodiversity of insects when such spraying is reduced. Bt eggplant targets the fruit and shoot borer and does not affect non-target or beneficial insects.
Because Bt eggplant significantly reduces the need for insecticides, the use of these new varieties leads to lower levels of insecticide residues in the soil and groundwater (Shelton et al 2002). This would offer significant environmental improvement.
The center of origin for eggplant is not clear. However, the maximum varietal distribution of eggplant may be observed in South and Southeast Asia. Researchers have studied eggplant crossing behavior and Bt eggplant behaves in a similar fashion. It does not show any changes in its pollen dispersal or crossability than has been reported in conventional eggplant. As the cry1-Ac gene does not confer any change in plant habit or behavior, it will have no impact on diversity.
Field tests have shown that there are no adverse effects resulting from pollen transfer from Bt eggplant to other plants because of genetic incompatibility.
Bt eggplant specifically targets the fruit and shoot borer and related pests such as the fruit borer and stem borer. As such it is ineffective against other insects. This helps ensure that beneficial insects and organisms continue to thrive and are not affected as usually occurs in the case of pesticide sprays.
Bt eggplant looks and has the same nutrient composition as the conventional eggplant except for the additional Bt protein that renders it resistant to the fruit and shoot borer. It retains the same nutritional value as non-Bt varities and feeding tests with different animal groups that included fish, chicken, rabbit, goat, rats, and buffalo revealed no toxicity or new allergenic compounds. Bt eggplant is likely to be lower in pesticide residues, and therefore healthier than conventional eggplant grown with regular applications of toxic insecticides.
Scientists and economists anticipate the following benefits to farmers:
- When used in conjunction with good farming practices, Bt eggplant crops will produce more undamaged fruit than non-Bt eggplant crops. Higher yields will lead to increased income for farmers.
- As the Bt eggplant will require fewer insecticidal sprays, farmer and farm workers’ exposure to insecticides will be minimized.
- The pricing of varieties distributed through the public system will be based on a cost-recovery model that aims to bring high-quality seeds to economically weaker farming communities in the region.
- Farmers will be able to continue the practice they currently follow for varieties and for hybrids.
Bacillus thuringiensis microbial formulations have been shown to be very specific to target insect pests. Tests have shown that Bt eggplant effectiveness is 100% pest mortality in shoots and fruits, compared to 30% or less with conventional pesticide-treated varieties.
Conventional insecticides are generally sprayed on crops to destroy pests. Insecticidal sprays are effective only during a brief window between the hatching of larvae and its penetration into the fruit and shoot of the plant. Once the larva bores into the plant, it is impervious to insecticidal sprays. To avoid this possibility, farmers tend to resort to saturation spraying, a process that not only adversely affects the environment, but also their health and that of the end consumers. These sprays also destroy non-target insects and organisms that are otherwise beneficial to agricultural plants and the local ecology. In Bt eggplant, the insecticidal protein is expressed by the plant itself and the borer is killed as it tries to bore into the plant. However, Bt eggplant is harmless to beneficial insects and non-target organisms.
How does genetically engineering fruit and shoot borer resistance into eggplant help farmers and consumers?
Currently, farmers use labor-intensive practices to control EFSB such as the prompt manual removal of wilted shoots. The trapping of male moths using pheromones to prevent mating and the use of nylon netting are also done to protect the plants. These efforts are usually insufficient, thereby forcing farmers to rely heavily on insecticide sprays. However, EFSB is only vulnerable to sprays for a few hours before it bores into the plant, forcing farmers to spray insecticides as often as every 2-3 days. The intensive use of insecticides poses a serious threat to human health and the environment. Heavy use of pesticide sprays also adds to the cost of production. With Bt eggplant, the farmers will gain increased productivity, profits, and health benefits while the consumers will get access to pesticide-free safer fruits. The increased productivity will help to maintain low prices for the consumer while the farmers will gain from higher marketable yields.
Eggplant is a primary source of cash income for resource-poor farmers in Bangladesh. Currently, 7.8 percent of the land under vegetable crops, 64,208, hectares is dedicated to growing about 340,000 metric tons of eggplant per annum. However, this is only 1.1 percent of the world’s production. Eggplant crop productivity is lower in Bangladesh than in neighboring countries. The main growing districts are: Bogra, Chittagong, Comilla, Dhaka, Dinajpur, Faridpur, Jamalpur, Jessore, Khagrachari, Khulna, Mymensingh, Rangamati, Rangpur, Rajshahi, Sylhet, and Tangail.
Consumers in many countries have been consuming Bt crops, or products derived from them since they were first commercialized in 1996. For example, about 30% of the world’s production of corn is protected from insect attack by a Bt protein very similar to the one in Bt eggplant.
Genetic engineering involves the introduction of a specific gene into the genome of a plant to obtain a desired trait. The gene introduced may come from another plant species or from any other organism. While traditional plant breeding involves crossing related plants, genetic engineering uses modern biotechnology tools that allow breeders to be more precise and enables the introduction of useful traits that are otherwise difficult or impossible to achieve by conventional means. The goals of genetic engineering are the same as with traditional breeding. Scientists may aim to improve crop performance in the field by conferring pest and disease resistance, herbicide resistance, or tolerance to environmental stresses (such as salinity and drought or flooding). They may also aim to develop products with enhanced value, such as improved post-harvest life, nutritional value, or other health benefits.
FSBR-eggplant refers to “fruit and shoot borer resistant” eggplant, which is also called Bt eggplant, and is eggplant that was evolved through genetic engineering. Eggplant is also known as eggplant or aubergine around the world. Contrary to popular misconception, the “Bt” in Bt eggplant does not stand for “Biotechnology”. It is actually short for Bacillus thuringiensis, a soil bacterium that harbors a gene called cry1-Ac. The cry1-Ac gene produces an insecticidal protein that is effective in controlling the larvae of certain moths that bore into and feed on the shoots, leaves, and fruit of plants like eggplant. This protein is toxic to a narrow range of insects but is not harmful to animals or humans. In the last few years, several crops have been genetically engineered to produce their own Bt proteins, making them resistant to specific groups of insects. Bt eggplant is genetically engineered to contain its own FSB resistance mechanism − the Bt gene, cry1-Ac.
Bt eggplant provides an effective environmentally friendly and economically sustainable solution to tackle crop losses resulting from fruit and shoot borer infestation. The cry1-Ac protein produced in Bt eggplant is similar in structure and activity to that found in nature and is already available and used commercially in the form of Bt-based biopesticides, often used by organic growers. However, pesticidal sprays are only effective during a brief window then the larvae hatches from the egg and bores into the fruit or shoot of the eggplant plant. Once the larvae takes refuge within the fruit they are safe from surface sprays however intensive they may be, and are free to destroy the crop from within. Bt eggplant, in which the cry1-Ac gene is genetically engineered into the eggplant, ensures a built-in resistance against the fruit and shoot borer larvae.
The experience of millions of consumers of Bt products for nearly 20 years and the use of Bt as a biopesticide for more than 80 years indicates an excellent track record of safety to humans and the environment. Scientists have conducted rigorous tests as per the stringent requirements of regulatory bodies to ensure that Bt eggplant is safe for human consumption.
- Nutritional content: Bt eggplant is compositionally identical to conventional eggplant except for the additional Bt protein. It, therefore, has the same nutritional value as non-Bt eggplant.
- Toxicity: Bt eggplant has been tested on a number of different animal groups to show that it is not toxic to any group. These include, but are not limited to, fish, chicken, rabbit, goat, rats and buffalo. These studies have confirmed the long history of food safety of the cry1-Ac protein to animals and humans.
- Allergenicity: The Bt eggplant has been tested to ascertain that it contains no new allergenic compounds and it is found to be non-allergenic.