In Raichur, bollworms scoff at Bt cotton

Unexpected resistance

For the last eight years genetically modified Bt cotton that produces its own toxin pushed up India’s cotton production from 2.3 million tonnes in 2002 to 5.4 million tonnes in 2008 with a jump in productivity from 302 to 567 kg per hectare.

The key to this success was a drastic reduction in bollworm attacks, thanks to the genetically-modified crop.

Bt cotton produces its own toxin to keep the caterpillars at bay and thereby help the farmers not only with improved productivity but also savings on pesticide sprays.

But researchers at University of Agricultural Sciences in Raichur and Institute of Wood Sciences an Technology in Bangalore showed Helicoverpa armigera, the most prominent among bollworms in India, surviving on commercial Bt-cotton hybrids containing single (Cry1Ac) and double (Cry1Ac and Cry2Ab) genes.

“This is perhaps the first demonstration of natural populations of H armigera being capable of surviving and breeding on commercial Bt hybrids in India,” the researchers reported in the journal “Current Science” on Friday.

The caterpillars not only survive on the bud, flowers and bolls of Bt cotton but also mate and produce offspring. In other words, they seem to have no problem whatsoever in what would otherwise be a highly poisonous environment for them.

“We will see more resistance in bollworms in the near future. Similar studies should be carried out in other regions to evaluate the situation on a national scale,” said Y B Srinivasa, a IWST scientist and member of the study team.

First field study

Even though there were laboratory studies in the past with similar result, this is the first field -level research from India which showed that natural boll-worm population in Raichur already had a built-in resistance. Reports from China were almost on identical lines.

Scientists, however, said it was not a matter of alarm as yet. “Resistance to Bt cotton is an inevitable eventuality and is certainly being delayed due to the introduction of an array of genes such as Cry2Ab and Cry1C. The future introduction of Cry1F and VIP genes do have the potential to delay resistance further,” Keshav Kranthi, director of Central Institute of Cotton Research at Nagpur told Deccan Herald.

India is probably the only country where nearly 90 per cent of area under cotton was converted to Bt cotton within a short span of eight years, with meagre compliance of resistance management strategies, thus accelerating adaptability of bollworm to Bt cotton, he said.

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