The Hindu : GM mustard

Online edition of India's National Newspaper
Wednesday, Dec 04, 2002

Opinion

Opinion - Leader Page Articles

GM mustard

By N. Gopal Raj

Thorny issues surround the use of the marker gene providing herbicide tolerance. Is that gene there only as a marker or is herbicide tolerance the driving motivation for developing this GM crop?

GENETICALLY MODIFIED (GM) crops are one of those topics which arouses great passion, with the protagonists unwilling to see any merit in the others' arguments. Those favouring the growing ability to directly modify genes see it as a logical extension, provided by new scientific knowledge, of the breeding process which humans have employed for centuries to advantage in agriculture. The ability to operate at the genetic level gives unparalleled flexibility in introducing new and beneficial traits, making the land more productive and reducing the use of harmful chemicals, they argue. But those opposing GM crops see it as a Frankenstein invention, a further and potentially more dangerous example of humanity's technical prowess overtaking its ability to use technology wisely.

In India, the Union Government's Genetic Engineering Approval Committee (GEAC), under the Department of Environment, Forests and Wildlife, has the final say on whether or not a GM crop can be released for commercial cultivation. Earlier this year, cotton, engineered for resistance to insect pests, became the country's first GM crop to be cleared for commercial cultivation. Now the GEAC must decide whether to allow release of India's first GM food crop, mustard.

The Delhi-based Proagro Seed Company, now part of the multinational Bayer CropScience, has genetically modified the Indian oilseed mustard (brassica juncea) for male sterility. As mustard is capable of self-pollination, such male sterile lines are required to create high-yielding hybrids. Once the two parental lines are crossed, male fertility has to be restored in their hybrid progeny or else no mustard seeds will be produced.

To achieve this, a bacterial gene called `barnase' is introduced into one parental line to stop pollen production. The other parental line is also genetically modified with another bacterial gene called `barstar' that blocks the action of the barnase gene. Their progeny with both barnase and barstar genes will be hybrids which are male fertile and therefore capable of normal seed production. In order to tell which plants have been genetically modified, the artificially introduced DNA also includes a marker gene (yet another bacterial gene called `bar') which makes these plants capable of tolerating the herbicide, glufosinate.

Although Proagro's GM mustard is the one nearing commercial release, a group at the University of Delhi South Campus too is developing a similar sort of GM mustard. When the GEAC met in early November, it decided to defer a decision on Proagro's GM mustard by a few weeks.

In the case of the Proagro mustard, one issue is its performance. According to the company, limited field trials were carried out in five north Indian States over four years between 1997-98 and 2001-02. This was followed by 41 largescale trials carried out by the company in 2001-02. Proagro says eight largescale trials were also done by the Indian Council of Agricultural Research during 2001-02, four of which were to test for agronomic characters and the other four for bio-safety.

The company claims that its GM mustard hybrids give at least 20 per cent more seed and oil, providing farmers an additional income of Rs. 3,500 to Rs. 4,500 per hectare. But ICAR officials say that their field trials do not show this GM mustard as having significantly superior performance. "In any case, the data from a single season is insufficient to assess agronomic performance," one of them told The Hindu.

Thorny issues surround the use of the marker gene providing herbicide tolerance. Is that gene there only as a marker or is herbicide tolerance the driving motivation for developing this GM crop? After all, herbicide tolerant crops accounted for over 80 per cent of the worldwide area under GM crops in 2000. A table from the Department of Biotechnology lists Proagro's GM mustard as intended "to develop better hybrid cultivars" while the purpose behind the University of Delhi South Campus' similar sort of GM mustard is given as "to generate herbicide tolerant plants".

Major agrochemical companies have developed GM crops which are tolerant to the herbicides they make. Bayers sells the glufosinate herbicide (under the Liberty and Basta names), as well as GM crops which can withstand this herbicide. But Proagro denies that its GM mustard is intended for this purpose. Basta was not registered for use with any of the agronomic crops in India, points out Alok Kumar, the company's manager for Biotechnology Regulatory Affairs.

At a time of concern over pollution, toxicity to animals and persistence of herbicides or their resides, herbicides such as glufosinate were useful for weed control, being highly effective at low dosage, safe for animals and rapidly degraded in the soil, points out a paper published in the journal Current Science by Deepak Pental and his research group at the University of Delhi South Campus. However, as such herbicides were not selective, they could only be used in conjunction with transgenic crops resistant to them. Such herbicides would allow no-till or low-till agriculture, conserving moisture, noted the paper.

There are concerns, too, about whether the bar gene for herbicide tolerance could spread. A report earlier this year from English Nature, the British Government's advisers on the environment, suggested that canola (closely related to Indian mustard) which was resistant to three herbicides, including Liberty, emerged in just two years as a result of cross-pollination.

It was currently impossible to prevent gene flow between sexually compatible species in the same area, observed Allison Snow, a plant ecologist at Ohio State University in the U.S, in a recent article in the journal Nature Biotechnology. A transgene for herbicide resistance could spread, but this would only be a problem if the herbicide was very important for controlling weedy populations of the wild relatives, she told The Hindu.

There were not many wild relatives of the Indian mustard to which the gene could be passed on and these grew in isolated areas, such as in the Northeast, according to K. R. Shivanna, former head of the Department of Botany at Delhi University, who has studied the mustard family. The risk was that wind and insects could carry pollen from the GM mustard and pollinate neighbouring non-GM mustard varieties, he points out. Farmers should not then face a situation, as had happened abroad, of being required to pay license fees because their plants now contained these genes.

Proagro had conducted pollen flow studies in the presence of bee hives six times over three consecutive years, according to Dr. Alok Kumar. The pooled data indicated that the pollen did not travel more than 35 metres and the extent of pollen flow was only 0.019 per cent. As required by the GEAC, the company had studied pollen flow in 2001-02, without beehives. The study showed that pollen from the transgenic plants travelled a maximum of 10 metres. Pollen flow studies carried out by the ICAR during 2001-02 showed that transgenic pollen spread up to 50 metres in three locations and travelled up to 75 metres at a fourth location. But the maximum pollen flow was observed at 10 metres, beyond which it decreased, adds Dr. Alok Kumar. Even if the bar gene were to spread, plants carrying this gene would still be vulnerable to any non-glufosinate herbicide, he points out.

Couldn't the whole problem be avoided by excising the marker gene after genetic transformation or having it separate out in subsequent generations? Retaining the herbicide tolerance marker gene was essential when male sterility was the trait being introduced, says Dr. Deepak Pental. His research group has demonstrated the feasibility of molecular excision of the marker gene in both cotton and mustard.

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