Abstract
Abstract. Cotton cultivation has made rapid strides in India since the introduction of Bt cotton, which provided effective protection against its major pest, Helicoverpa armigera and other bollworms. The presence of alternate host crops for cotton bollworms targeted by Bt cotton play a key role in resistance evolution to the in planta expressed Bt proteins. Several host crops for H. armigera such as pigeonpea, sorghum, tomato, chilli, sunflower and corn are cultivated alongside Bt cotton. Change detection in the extent of cotton and alternate host crops of cotton bollworm was conducted using IRS LISS-III data in Punjab, Haryana, Rajasthan, Gujarat, Maharashtra, Andhra Pradesh and Karnataka states. The changes in the extent of cotton and host crops were monitored using multi-temporal data of 2002, 2004 and 2008. The results indicated that Bt cotton (Hirsutum) has almost completely replaced the traditional Indian cotton (Gossypium arborium). Several alternate host crops of H. armigera were grown along with cotton. Pigeonpea was the major host crop in almost all the locations. Chilies dominated in Andhra Pradesh, sunflower in Karnataka and corn in Gujarat. These host crops serve as ‘natural’ refuge of H. armigera and possibly, for this reason this pest has not evolved resistance to the Bt expressed by Bollgard II even after 16 seasons of intensive cultivation; whereas the pink bollworm, a monophagous cotton bollworm, had developed resistance to Cry1Ac in 2009 and to Cry1Ac and Cry2Ab in 2015.
Highlights
1.1 Status of cotton cultivation and importance of host crops in IndiaCotton covers an area of approximately 9 million ha in India representing about one quarter of the global area of 35 million ha under the crop
The results of the present study indicate that Hirsutum (Bt) cotton has almost replaced completely the traditional Indian cotton in all the states
The Percent Tolerance Interval (PTI) indicates that proportion of cotton remains below 85% in seven out of 10 locations even under high cotton adoption in seven out of ten blocks
Summary
1.1 Status of cotton cultivation and importance of host crops in IndiaCotton covers an area of approximately 9 million ha in India representing about one quarter of the global area of 35 million ha under the crop. Engineered cotton carrying an insecticidal protein, Cry1Ac, derived from the common soil bacterium Bacillus thuringiensis (Bt) has been developed against major cotton bollworms. Helicoverpa armigera (Hübner), the American bollworm, is a major pest of many economically important crops including cotton, pigeonpea, chickpea, sunflower, tomato, sorghum, millet, okra and corn (Manjunath, 1989; Sharma, 2001). These crops suffer extensive damage and the pest is difficult to control as it has developed resistance to several chemical insecticides.
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