Opinion - News Analysis   

Is Bt cotton unsuitable?

K.R. Kranthi

Bt cotton is the most potent and best available option for bollworm management in the country.

SUMAN SAHAI wrote in The Hindu of August 29, 2005, that our research article (Kranthi et al., Current Science, July 25, 2005) gives scientific reasons for the failure of Monsanto Bt cotton varieties in India. She points out that our paper shows that the technology is faulty and does not protect against the bollworm; hence the Genetic Engineering Approval Committee (GEAC) must be made accountable for the losses for poor farmers. Dr. Sahai argues further that because this information was available by the end of 2003, the Director-General, Indian Council of Agricultural Research (ICAR), who is an ex-officio member of the GEAC, should have raised his voice to stop any further releases of Bt cotton. Does our research paper support her argument? It does not.

Our report does not provide evidence to say that the technology is ineffective or flawed, as Dr. Sahai wants the world to believe. It shows that the technology works for most part of the season, but also has a few inherent inadequacies. That does not take away the merit of the technology. It only asks for improvements to be made. We never mentioned in the Current Science paper or elsewhere that the technology was ineffective or unsustainable as it is made out to be. Despite the shortcomings mentioned in our paper, Bt cotton is still the most potent and best available option for bollworm management in India. Even the best of the currently available pesticides do not kill more than 70-80 per cent bollworm larvae under field conditions, which Bt cotton does. Hence, the Bt technology is considered to be more effective than the best of currently recommended pesticides against H. armigera.

Unmatched bio-safety

With an unmatched bio-safety profile, incomparable to that of conventional pesticides, Bt cotton is most sought after by farmers not just because of its efficacy in effective bollworm control, but also because it makes cotton cultivation easier and healthier with fewer pesticides to spray. If anything, the GEAC had been over-cautious in releasing Bt cotton in India. The approvals were also based on our own results of three-year scientific field trial evaluation data, which consistently showed yield and ecological benefits from Bt cotton despite the minor inadequacies in toxin expression. I have had a chance to attend a few GEAC meetings as an invited expert. If our data were detrimental to the Indian farmer's interest, wouldn't I have pointed out this to the members when I attended these meetings? So would have the Director-General of ICAR, who is known to be forthright with his views on all issues concerning good science and technologies for farmer welfare. Bt cotton has now been endorsed by thousands of farmers ever since its introduction in 2002, as can be seen from immense popularity and enormous technology adoption rate. It is unfortunate that the NGOs are trying to wage a meaningless war against the GM technology by misinterpreting some selective portions of our scientific paper.

Indeed, our paper describes the seasonal decline of Cry1Ac toxin levels and its variability in various plant parts of a few Bt cotton hybrids. We also said that, "the toxin expression in the boll-rind, square bud and ovary of flowers was clearly inadequate to confer full protection to the fruiting parts." Interestingly two papers were published from China and Australia around the same time in 2005, in an American journal, Journal of Economic Entomology, describing almost similar data to point out a seasonal decline of the Cry1Ac toxin in their Bt cotton varieties and low toxin levels in ovules and bolls. Does this make Bt cotton ineffective against bollworm? The answer is `no'.

We said in our paper very clearly that "despite the variability in toxin expression, the pest control properties are unlikely to be affected significantly at least until the crop becomes 100-115 days old. Though some larvae survived on various plant parts in invitro bioassays, the surviving larvae on all the parts were stunted with a weight reduction of 48.8 to 98 per cent, compared to the larvae on non-Bt cotton plants." The cotton bollworm (Helicoverpa armigera) generally infests cotton 60-120 days after sowing. While Bt cotton is highly effective 60-115 days after sowing, there are chances of bollworm causing damage during the remaining one to two weeks. We therefore recommended pest scouting and need-based supplemental sprays for this period. We did not mention in our paper a commonly known fact that majority (70-80 per cent) of bollworm eggs are laid on leaves of the upper canopy and neonate larvae scrape and feed on the surface of the leaf soon after hatching and get killed. Eggs laid directly on flowers or a few other fruiting parts may survive, depending on the levels of toxin expression. Thus in an overall analysis, Bt cotton controls at least about 70-80 per cent of bollworm infestation. This is very significant in economic and environmental terms.

We never said that Cry1Ac expression was more in varieties compared to hybrids. We speculated that the relatively higher efficacy of Bt cotton varieties on H. armigera in China and Australia may have been because of the use of straight varieties in these countries compared to the use of hybrids in India. However, the recent data published on the Bt cotton varieties of China and Australia — showing expression levels in their varieties similar, if not less than, to those of the hybrids in India — do not support this speculation either. However, I would like to re-emphasise that Bt straight varieties would have the advantage of Cry1Ac expression in all of the seeds in green bolls as against the segregating 75 per cent Bt seeds in the bolls of F1 hybrid plants as mentioned in our paper. Hence Indian researchers including our own group at the Central Institute for Cotton Research (CICR), Nagpur, must intensify the efforts to develop Bt straight varieties for the use of Indian farmers.

Why did we publish this data? We wanted farmers to appreciate what exactly was to be expected from the technology. Importantly, our main intention was to assess the strengths and weaknesses of the technology so that it can be improved further. We pointed out some inherent inadequacies that need to be addressed by all concerned so that the technology can become more potent. We suggested that, "1. Biotechnology efforts in India should focus on developing transgenic cotton varieties with tissue specific promoters to enhance the expression of the toxin genes in fruiting parts, and 2. The choice of parental background is crucial for sustainable expression of the Cry1Ac transgene and therefore seed companies should evaluate their hybrids critically for highest levels of expression in fruiting parts and also for relatively effective level of toxin expression late in the season." We concluded our paper by making our objective clear that, "Since the Bt-transgenic technology has thus far proven itself to be one of the most environment-friendly methods of bollworm management, it is in the interest of the technology itself that researchers, technology providers and administrators ensure that it must be provided to the farmers in a form which gives the best possible returns for the investment."

I earnestly hope that the meaningless hullabaloo raised over Bt cotton by the NGOs comes to an end soon and that a brilliant technology such as Bt cotton, which is state-of-the-art in eco-friendly cotton pest management, will be improved further and stabilised in good varieties and hybrids so as to ensure a pesticide-free profitable and sustainable cotton pest management in India.

(The writer is Senior Scientist, CICR, Nagpur.)

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