THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
10 August 2005
RE: Bt Cotton Problems in India
Following our mailout on 5 July 2005, "Bt Crops and Insect Resistance", new research (Item 1) has emerged that further supports earlier findings that the levels of toxin emitted by Bt crops varies and at times is insufficient to kill the targeted pests. This could lead to greater use of pesticides, and furthermore, fluctuations in the efficacy of Bt crops, to the extent that some insects survive, provide opportunities for insects to develop resistance to the Bt toxin.
Scientists at the Central Institute
of Cotton Research in India, in a study of Bt cotton, found that the amount
of cry1Ac protein in Bt cotton varies across different varieties and,
in some plants, decreases 110 days after sowing to levels that are inadequate
to protect the plants from bollworm attacks.
The study can be downloaded
This problem, however, is not particular to India alone as shown by studies from China and the United States (Items 2 and 3). All these indicate that the problem associated with Bt cotton is not necessarily confined to Indian varieties or to growing conditions in India.
In a separate study (Item 4), also by scientists at the Central Institute for Cotton Research, it was found that increasing reliance on a single gene in growing a variety of crops to make them resistant to bollworms could be dangerous and could lead to greater resistance among the pest population.
A model simulating the development of insect resistance to Bt cotton predicts that such monoculture could lead to resistance within a few years in India where the growing of Bt crops are increasing rapidly.
This study is published in Current Science 87, 1593_1597 (2004) of December 2004, a Indian Academy of Science publication.
These important lessons from India should be studied seriously by other countries which are either growing similar crops or are attempting to introduce such crops in their territories, lest they also travel down the same road.
Chee Yoke Heong
Govt study spies genetic cotton
New Delhi, July 26: Government scientists have acknowledged flaws in the genetically modified Bt cotton plants under commercial cultivation, virtually endorsing what non-government organisations have been claiming for long.
However, biotechnology company Monsanto, which provided the technology to create the plants, said Bt cotton had gained acceptability among farmers and done well in the past three years.
The Bt cotton varieties are designed to make a protein, cry1Ac, that kills bollworms when they gorge on the plants. But scientists at the Central Institute of Cotton Research have reported that the amount of protein is not always enough to kill the insects.
In a study released yesterday, the Nagpur-based scientists said the amount of protein varies across different varieties and, in some plants, decreases to levels that are inadequate to protect the plants 110 days after sowing.
Their experiments also revealed that production of the protein is lowest in the bollworms' most favoured sites of attack -- the plants' ovaries found in the flowers and the thick green peel of the cotton boll from which cotton blooms.
"The most vulnerable parts of the plants thus do not have adequate cry1Ac to kill the pest," said Keshav Kranthi, a senior scientist at the institute of cotton research and lead investigator of the study published in the journal Current Science.
These findings, the researchers said, explain farmers' complaints that bollworms survive on Bt cotton plants. Farmers would have to be "mentally prepared for the possibility of extra applications of insecticides to control bollworms," a scientist said.
The pest-killing ability of the Bt cotton varieties stay intact for about
110 days, the study showed. But cry1Ac levels decline steadily as the plants grow and drop to below the critical "lethal level" of 1.9 micrograms by 110 days.
"This study validates our findings and proves that Bt cotton in India was approved without adequate field testing," said Suman Sahai, director of Gene Campaign, a New Delhi-based NGO that has been demanding greater transparency in genetic engineering issues.
Sahai said India's regulatory agencies should have ascertained whether the plants produce the protein in the right amounts and on the right sites in the plant before approving it for commercial cultivation. "Why weren't rigorous studies such as this one conducted earlier?" she asked.
"We're now asking ourselves the same question," a government entomologist said.
The Bt cotton plants carry a gene from a bacteria called Bacillus thurigiensis (Bt) that allows the plants to produce the cryAc1 protein which is toxic to bollworms.
A spokesperson for Monsanto said Indian farmland under Bt cotton has grown from 72,000 hectares in 2002 to over 1.2 million hectares in 2004. Last year, over 350,000 farmers had planted Bt cotton.
"A majority of farmers in India have managed crops with minimal insecticide sprays for control of bollworms," the spokesperson said.
But the research institute
data shows that Bt cotton in India may require more supplemental insecticide
sprays than Bt cotton elsewhere in the world.
J Econ Entomol. 2005 Feb;98(1):195-201.
Seasonal expression profiles of insecticidal protein and control efficacy against Helicoverpa armigera for Bt cotton in the Yangtze River valley of China.
Wan P, Zhang Y, Wu K, Huang M.
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100094, China.
Seasonal levels of Bacillus thuringiensis (Bt) insecticidal protein and its control efficacy against Helicoverpa armigera (Hubner) in Bt transgenic cotton GK19 (carrying a Cry1Ac/Cry1Ab fused gene) and BG1560 (carrying a Cry1Ac gene) were investigated in Tianmen County, Hubei Province, located in the Yangtze River valley of China, in 2001 and 2002. The results showed that the toxin content in Bt cotton changed significantly over time, and that the structure, growth stage, and variety were significant sources of variability. Generally, insecticidal protein levels were high during the early stages of cotton growth; they declined in mid-season, and rebounded in late season. On most dates sampled, the toxin contents in leaf, square, petal, and stamens (including nonovule pistil tissue) were much higher than those in ovule and boll. Compared with BG1560, the expression of Cry1Ac/Cry1Ab protein in GK19 was more variable during the whole growth period of cotton. The field evaluation on larval population dynamics of H. armigera in Bt and conventional cotton showed that the larval densities in BG1560 and GK19 fields decreased, respectively, 92.04 and 81.85% in 2001, and 96.84 and 91.80% in 2002.
J Econ Entomol. 2004 Oct;97(5):1737-44
Relative concentration of Cry1A in maize leaves and cotton bolls with diverse chlorophyll content and corresponding larval development of fall armyworm (Lepidoptera: Noctuidae) and southwestern corn borer (Lepidoptera: Crambidae) on maize whorl leaf profiles.
Abel CA, Adamczyk JJ Jr.
USDA-ARS Southern Insect Management Research Unit, P.O. Box 346, Stoneville, MS 38776, USA.
To manage insect resistance to transgenic crops that express insecticidal proteins from Bacillus thuringiensis (Bt) Berliner, the U.S. Environmental Protection Agency recommends a refuge-based insect resistance management strategy where a percentage of non-Bt (refuge) crop is grown in proximity to a Bt-expressing crop. An important requirement for this strategy is that the toxin exists at a high effective dose for control of the target pest(s), so that heterozygous individuals in the population do not reach adulthood. Factors that cause reduced levels of toxin in the plant are a threat to this strategy.
We quantified Cry1Ab from different areas of the maize, Zea mays L., leaf. In general, the distal tip of the V7 maize leaf had a higher concentration of Cry1Ab compared with the middle section of the V7 leaf, and the middle section of the developing V9 leaf had the lowest concentration of Cry1Ab. When these sections of maize tissue were fed to fall armyworm, Spodoptera frugiperda (J.E. Smith), and southwestern corn borer, Diatraea grandiosella Dyar, there was not a reduction in development or an increase in mortality with tissue that had higher concentrations of toxin. Another study tested the relative concentration of Cry1Ab between the white-yellow, yellow-green, and green portions of the developing ninth leaf within the maize whorl. There were differences in Cry1Ab concentration among these leaf areas. The green tissue had the highest concentration of toxin followed by the yellow-green and white-yellow tissues. Correlations between concentration of Cry1Ab and 5-d fall armyworm larval weights among the three leaf color profiles were all significant and negative, i.e., decreased concentration of Cry1Ab in the leaf tissue resulted in increased 5-d larval weights. There was 100% mortality to the southwestern corn borer larvae fed Cry1Ab maize leaf tissue. Differences in the amount of Cry1Ab in the developing V9 leaf profiles did not alter the absolute susceptibility of the southwestern corn borer to the toxin.
In cotton, Gossypium hirsutum L., the amount of Cry1Ac was significantly lower in boll tips where flowers had remained attached compared with normal boll tips. Boll tips where the flowers remained attached are often the site where corn earworms, Helicoverpa zea (Boddie), penetrate Bt cotton bolls. This study demonstrated that, in two diverse plant species, tissue that has low chlorophyll content does not fully express Cry1A. Photosynthesis regulating factors related to mRNA transcription and translation should be studied for their effect on Cry1A production and insect control.
Indian Bt gene monoculture,
potential time bomb
Increasing reliance on a single gene in growing a variety of crops to make them resistant to bollworms could be dangerous, warn experts. Resistance is looming large among Bt crops in India.
In March, this year, an unprecedented number of hybrids of Bacillus thuringiensis (Bt)-resistant cotton will be planted in India. A recent model simulating the development of insect resistance to Bt cotton predicts that such monoculture could lead to resistance within a few years. The risk of resistance as a consequence of gene monoculture is higher in India where Bt crops are planted illegally than in other countries producing transgenic crops.
Next month 12 new Bt cotton hybrids will enter the Indian market--all carrying the same cry1Ac gene licensed from US seed giant Monsanto. Four of the six Indian companies that have licensed the gene--including Mahyco in Jalna, Raasi Seeds in Attur, Ankur Seeds Limited in Nagpur and Nuzhiveedu Seeds in Hyderabad--will each release three Bt hybrids. Bt cotton carrying cry1Ac to confer resistance against bollworms (Helicoverpa armigera) was initially exclusively licensed to Jalna-based Maharashtra Hybrid Company--also known as Mahyco--the Indian partner of Monsanto of St. Louis, Missouri, in 2002 (Nat. Biotechnol. 20, 415, 2002).
Keshav Kranthi, a senior scientist at the Central Institute for Cotton Research in Nagpur in the Indian province of Maharashtra and colleagues, warned of the risk of pest resistance to Bt varieties currently used in India in a paper published in the Indian Academy of Science publication Current Science 87, 1593_1597 (2004) last December. The authors established a theoretical model to predict resistance development in bollworms due to overuse of the cry1Ac gene. The 'Bt-Adapt model' simulates the bollworm's adaptation to the toxin, depending on the number of generations of the insect exposed to Bt every year and on the number of different Bt crops the insects encounter.
The first estimate is based on two to three generations of insects exposed each year to a single Bt crop. "If the area under Bt cotton gets to 70_80% in a 100_200 kilometer radius, our model estimates resistance development [in] 3_4 years," Kranthi said. "So, it wouldn't be surprising to find Bt-cotton crop failures in some parts of India, starting with [in the province of] Gujarat in a couple of years from now," he adds.
But the Bt-Adapt model can also predict the consequences of exposing bollworms to more than one Bt crop (e. g. cotton and potato). If the number of generations of insects exposed to Bt crops increases to five or six--a likely scenario when another Bt crop is included--the rate of resistance development, according to the model, would be accelerated to half the time it now takes with only Bt cotton.
This scenario is not so unlikely given the increasing reliance on cry1Ac in other crops in India. "Over 42% of the projects in biotechnology research use this Bt gene," says Suman Sahai, convener of Delhi-based Gene Campaign, a nongovernmental organization, and visiting professor of genetics at Hamburg University. "We are going to face a situation when a wide range of crops, from cotton to potato, rice, maize, brinjal [eggplant], tomato, cauliflower, cabbage, even tobacco, carrying the Bt gene will be growing next to each other," warns Sahai.
By contrast, other countries have made limited use of the gene, and have refugia and monitoring strategies. Commercial crops with the cry1Ac gene in the US are limited to cotton and corn, and the gene has been used in research on potatoes. China is using cry1Ac in at least one of the three GM rice crops for which approval has been sought for commercial release (Nat. Biotechnol. 22, 642, 2004) and in its commercialized cotton, which was individually developed both by Monsanto and by its own scientists. Meanwhile, Argentina, Columbia and Mexico grow the Monsanto Bt cotton commercially and Uruguay and Brazil carry out field trials. Currently, the potential for illegal planting and associated resistance outbreak is the strongest in Brazil.
Though no resistance breakdown has been observed in fields in India yet, "it is important to remain guarded," warns Kottaram Krishnadas Narayanan, managing director of MetaHelix, in Bangalore, a crop biotechnology company. "Genetic uniformity is really dangerous," adds Says Ebrahimali Siddiq, board member of the International Rice Research Institute in Manila, the Philippines. "Resistance can break down any day."
"This kind of a situation is unique to India," explains Kranthi. Until now, a refugia strategy, not strictly implemented and widely undermined by illegal planting of Bt cotton, was the only strategy to avoid resistance in India (Nat. Biotechnol. 22, 1333_1334 (2004)). "Unlike the US, non-Bt cotton refuges are not required in India," explains Bruce Tabashnik Professor at the Department of Entomology at the University of Arizona in Tucson. "If all or most of the other crops eaten by Helicoverpa armigera produce cry1Ac and cotton produces cry1Ac, refuge production of susceptibles might not be adequate to stem resistance."
Fears of early resistance development due to gene monoculture is already forcing Monsanto to develop stacked genes thus shifting the focus to other genes. And Syngenta India, in Pune, started to develop cotton with an unrelated type of Bt toxin (vip3). "We need other genes not only to delay resistance but to bring seed price down through competition," concludes Prabhakara Rao managing director of Nuzhiveedu Seeds.