T. V. Padma, SciDev.Net

A study* has found that Indian varieties of cotton that have been genetically modified to resist an important insect pest are "inadequate".

The findings back farmers' claims that the pest, known as the bollworm, is able to survive on Bt cotton varieties, modified to resist it.

Prompted by the study, the president of an agricultural lobby group in India is demanding an enquiry into whether the government continued to release the "inadequate" varieties, despite knowing their shortcomings.

The researchers, who published their findings in the Indian journal Current Science last week (25 July), say farmers may have to be prepared to use additional insecticide in the later stages of growing the crop.

Bt cotton is genetically modified to produce a toxin lethal to bollworms, which cause an estimated US$1 billion worth of damage in India each year. It is patented and sold by the US firm Monsanto.

In Australia, China, Indonesia, and South Africa farmers grow Monsanto's Bt cotton as it is sold by the company. In India however, under a license from Monsanto, the Bt cotton is repeatedly crossed with Indian varieties to adapt it to the country's wide range of growing conditions.

The Indian government cleared the first three hybrid cotton varieties for commercial cultivation in 2002. More were cleared for planting in subsequent years.

In 2003, scientists from the Indian Central Institute for Cotton Research (CICR) tested eight commercially grown hybrids. They found that some hybrids produced up to seven times as much toxin as others. In addition, differing amounts of toxin were found in different parts of individual plants.

Generally, the ovaries of the flowers and the rinds of the cotton bolls, which are favoured by the bollworm, contained the least amount of toxin, while leaves contained the highest levels. The amount of toxin declined progressively as the plants grew, and dropped below effective levels 100 days after the seeds were sown.

The toxin levels in the boll rind and flowers are "clearly inadequate" to fully protect the fruiting parts of the plant against the bollworm, the scientists report.

They say the findings help to explain complaints from Indian farmers that bollworms can survive on Bt cotton plants.

Several non-government organisations, including Greenpeace, the Dehli-based Gene Campaign and the Rural Foundation for Science, Technology and Environment, have reported instances of farmers complaining of Bt crop failure, but these were dismissed by the government and scientists as unsubstantiated.

On Wednesday (3 August) Suman Sahai, the president of Gene Campaign, wrote to the secretary of India's Ministry of Environment and Forests demanding an enquiry into whether the government released more Bt cotton hybrids for commercial cultivation despite knowing the early trends of CICR findings.

Already in 2003, the CICR filed a report to the Genetic Engineering Approval Committee, a body of the environment ministry, indicating that the levels of toxin in Indian Bt cotton might be insufficient to control the pest.

In her letter to the ministry, Sahai says the approval committee violated India's 1986 Environment Protection Act by not making CICR's early findings public.

The committee's website provides access to the 2002-2003 and 2004-2005 CICR reports, but not to the 2003-2004 report which, according to Sahai, would have contained its preliminary results on Indian Bt cotton.

Sahai has sent copies of her letter to the Indian prime minister and the minister for the environment. Neither has yet responded.

The secretary of the environment ministry told SciDev.Net the ministry has not yet received Sahai's letter.

Reference: Current Science 89, 291 (2005)

* Temporal and intra-plant variability of Cry1Ac expression in Bt-cotton and its influence on the survival of the cotton bollworm, Helicoverpa armigera (Hübner) (Noctuidae: Lepidoptera)
K. R. Kranthi*, S. Naidu, C. S. Dhawad, A. Tatwawadi, K. Mate, E. Patil, A. A. Bharose, G. T. Behere, R. M. Wadaskar and S. Kranthi
Central Institute for Cotton Research, P.B. No. 2, Shankarnagar PO, Nagpur 440 010, India

ABSTRACT

The quantitative levels of Cry1Ac and the seasonal decline in expression differed significantly among the eight
commercial Bollgard hybrids tested. The Cry1Ac expression was found to be variable among the hybrids and also between different plant parts. The leaves of Bt-cotton plants were found to have the highest levels of Cry1Ac expression followed by squares, bolls and flowers. The toxin expression in the boll-rind, square bud and ovary of flowers was clearly inadequate to confer full protection to the fruiting parts. Increasing levels of Helicoverpa armigera survival were correlated with the toxin levels decreasing below 1.8 mg/g in the plant parts. Genotype-independent seasonal decline of the Cry1Ac toxin levels was observed in all the hybrids. Cry1Ac expression decreased consistently as the plant aged. The decline in Cry1Ac was more rapid in some hybrids compared to others. The choice of parental background appeared to be crucial for sustainable expression of the cry1Ac transgene. The implications of variability in Cry1Ac expression and the seasonal decline on bollworm management are discussed.

Full paper in Current Science in PDF format: http://www.ias.ac.in/currsci/jul252005/291.pdf