New Horizons in Insect Science Towards Sustainable Pest Management

95

Carboxylesterase and Glutathi-

one-S-Transferase Quantification

Mediating Resistance in

Populations of Rice Leaf Folder,

Cnaphalocrocis medinalis (Guenee)

Ramesh Babu Veegala and Shashi Vemuri

A. K. Chakravarthy (ed.), New Horizons in Insect Science: Towards Sustainable Pest Management,
DOI 10.1007/978-81-322-2089-3_10, © Springer India 2015

R. B. Veegala ()
Crop Protection Division, CRIJAF, Barrackpore, West
Bengal, 700120 India
e-mail: [email protected]

S. Vemuri
AINP on Pesticide Residues, EEI Premises, ANGRAU,
Rajendranagar, Andhra Pradesh, 500030 India
e-mail: [email protected]

Abstract

A study was taken up for cross resistance between Bacillus thuringiensis

Cry toxins and synthetic insecticides in larvae for two field populations

of Cnaphalocrocis medinalis collected from the Directorate of Rice Re-

search (DRR) and ICRISAT using the leaf-dip bioassay method. Bioassays

with third instar larvae were carried out for two selected rice leaf folders,

C. medinalis field populations with monocrotophos. The bioassay results

showed a twofold difference in the resistance ratios for the two popula-

tions. Qualitative and quantitative changes of carboxylesterase (CarE) and

glutathione-s-transferase (GST’s) were worked out with midgut extracts

of the two C. medinalis populations of α-napthyl acetate and chloro di-

nitro benzene substrates. The results revealed a 1.35-fold and 2.245-fold

more variation in CarE and GST’s in midgut homogenates of the two

populations. Midgut and whole body extracts of the resistant C. medinalis

showed difference in the esterase banding pattern with midgut producing

three esterase bands. Inhibitor studies of the esterase isozymes separated

under native PAGE with specific esterase inhibitors DDVP, eserine, and

serine sulphate at different concentrations revealed esterase isozymes are

B type esterases and were associated with carboxyl esterase activity.

Introduction

The rice leaf folder (RLF), Cnaphalocrocis me-

dinalis (Guenee) (Lepidoptera: Pyralidae) is an

important rice pest, widely distributed in many

rice growing areas of Asia (Cheng 1996 ).There

have been frequent and serious outbreaks of this

Keywords

Carboxylesterase · Cnaphalocrocis medinalis · Glutathione-s-transferase ·

Isozymes