Responsiveness of entomopathogenic fungi to menadione-induced oxidative stress Rosana F. F. AZEVEDO a , Roberta K. F. SOUZA a , Gilberto U. L. BRAGA b , Drauzio E. N. RANGEL a, * a Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Para  ıba, S~ ao Jos e dos Campos, SP 12244-000, Brazil b Faculdade de Ci^ encias Farmac^ euticas de Ribeir~ ao Preto, Universidade de S~ ao Paulo, Ribeir~ ao Preto, SP 14040-903, Brazil article info Article history: Received 25 April 2014 Received in revised form 29 August 2014 Accepted 12 September 2014 Available online 28 September 2014 Corresponding Editor: Richard A. Humber Keywords: Conidial germination Median lethal concentration Minimum inhibitory concentration ROS inducers Stress biology abstract Entomopathogenic fungi are predisposed to ROS induced by heat and UVeA radiation when outside the insect host. When inside the host, they are subject to phagocytic cells that gener- ate ROS to eliminate invading pathogens. The oxidative stress tolerance of the entomopatho- genic fungi Aschersonia aleyrodis (ARSEF 430 and 10276), Aschersonia placenta (ARSEF 7637), Beauveria bassiana (ARSEF 252), Isaria fumosorosea (ARSEF 3889), Lecanicillium aphanocladii (AR- SEF 6433), Metarhizium acridum (ARSEF 324), Metarhizium anisopliae (ARSEF 5749), Metarhizium brunneum (ARSEF 1187 and ARSEF 5626), Metarhizium robertsii (ARSEF 2575), Tolypocladium cy- lindrosporum (ARSEF 3392), Tolypocladium inflatum (ARSEF 4877), and Simplicillium lanosoniveum (ARSEF 6430 and ARSEF 6651) was studied based on conidial germination on a medium sup- plemented with menadione. Conidial germination was evaluated 24 h after inoculation on potato dextrose agar (PDA) (control) or PDA supplemented with menadione. The two Ascher- sonia species (ARSEF 430, 7637, and 10276) were the most susceptible fungi, followed by the two Tolypocladium species (ARSEF 3392 and 4877) and the M. acridum (ARSEF 324). Metarhizium brunneum (ARSEF 5626) and M. anisopliae (ARSEF 5749) were the most tolerant isolates with MIC 0.28 mM. All fungal isolates, except ARSEF 5626 and ARSEF 5749, were not able to germi- nate at 0.20 mM. ª 2014 The British Mycological Society. Published by Elsevier Ltd. All rights reserved. Introduction Insect-pathogenic fungi are important biological control agents used in several countries as an alternative to chemical insecticides (Alston et al. 2005). When used as mycoinsecticides on crops, fungi are subject to oxidative stress caused by solar UV-A radiation (Griffiths et al. 1998), thermal solar radiation (Fridovich 1978), and starvation (Jakubowski et al. 2000). How- ever, when living inside the host, they may be inactivated by re- active oxygen species (ROS) produced by phagocytic cells of the infected insect’s immune system (Lavine & Strand 2002). Oxi- dative stress caused by ROS is an immune response to elimi- nate invading microorganisms (Lavine & Strand 2002). The first line of defense against oxidative stress is the en- zyme superoxide dismutase (SOD), which takes superoxide, which is a harmful ROS, and converts it to hydrogen peroxide, another ROS (Missall et al. 2004). Catalase and peroxidase also protect the cell by degrading hydrogen peroxide into oxygen and water. Once in cells, these enzymes limit ROS levels and minimize its damage (Missall et al. 2004). Cellular antioxidants * Corresponding author. Tel.: þ55 12 3947 1163. E-mail addresses: drauzio@pq.cnpq.br, drauzio@live.com (D. E. N. Rangel). journal homepage: www.elsevier.com/locate/funbio fungal biology 118 (2014) 990 e995 http://dx.doi.org/10.1016/j.funbio.2014.09.003 1878-6146/ª 2014 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.