Inheritance of Resistance in Indian Helicoverpa Armigera (Hubner) to Cry1Ac Toxin of Bacillus Thuringiensis

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Crop Protection 25 (2006) 119–124

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Inheritance of resistance in Indian Helicoverpa armigera (Hubner) to

Cry1Ac toxin of Bacillus thuringiensis

K.R. Kranthi , C.S. Dhawad, S.R. Naidu, K. Mate, G.T. Behere, R.M. Wadaskar, S. Kranthi

Central Institute for Cotton Research, P.B. No. 2, Shankarnagar PO, Nagpur 440 010, India

Received 31 January 2005; received in revised form 7 February 2005; accepted 21 March 2005

Abstract

The mode of inheritance of resistance to Cry1Ac toxin of Bacillus thuringiensis in the cotton bollworm, Helicoverpa armigera (Hubner), was elucidated through bioassay analysis of the response of resistant, susceptible, F1 hybrid and backcross H. armigera progeny to Cry1Ac using semi-synthetic diet and transgenic Bt cotton plants. The dominance value estimates ranged between 0.42 and 0.57. Resistance was found to be monogenic, autosomal and inherited as a semi-dominant trait. Genetic studies of response of H. armigera to transgenic Bt cotton showed that the effective resistance on transgenic Bt cotton plants was also inherited as a semi- dominant trait.

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Keywords: Helicoverpa armigera; Bt cotton; Inheritance; Resistance; Cry1Ac

1. Introduction

Transgenic cotton incorporating Cry1Ac gene derived from Bacillus thuringiensis (Bt) is one of the most exciting advances made in cotton pest management in recent times. The cotton bollworm Helicoverpa armigera (Hubner) is one of the main target pests of Bt cotton technology in India. It has a history of developing resistance to almost all the insecticides used for its control (Kranthi et al., 2002). Cry1Ac is the most toxic of the Bacillus thuringiensis insecticidal proteins to H. armigera (Padidam, 1992; Akhurst and...