Combined Use Of Streptomyces Sp. A6 And Chemical Fungicides Against Fusarium Wilt Of Cajanus Cajan May Reduce The Dosage Of Fungicides Required In The Field

Crop Protection 30 (2011) 770e775

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Crop Protection
journal homepage: www.elsevier.com/locate/cropro

Combined use of Streptomyces sp. A6 and chemical fungicides against fusarium wilt of Cajanus cajan may reduce the dosage of fungicides required in the field
Anil Kumar Singh, H.S. Chhatpar*
Department of Microbiology and Biotechnology Centre,Faculty of Science, Maharaja Sayajirao University of Baroda, Vadodara 390 002, India

a r t i c l e i n f o
Article history: Received 17 May 2010 Received in revised form 7 March 2011 Accepted 7 March 2011 Keywords: Biological control agents (BCAs) Fungicides Fusarium wilt Integrated pest management (IPM) Mycolytic enzymes Streptomyces Synergism

a b s t r a c t
Biological control agents offerone of the best alternatives to reduce the use of pesticides. This investigation studied the tolerance to fungicides and integrated use of the potential biocontrol agent Streptomyces sp. A6 for control of Fusarium wilt of pigeon pea, Cajanus cajan. Streptomyces sp. A6 exhibited strong tolerance towards most of the fungicides used in the study at concentrations higher than those recommended for fieldapplications. The isolate showed enhanced growth and mycolytic enzyme production in the presence of sulphur, mancozeb, carbendazim, fosetyl aluminium and triadimefon. The fungicides mancozeb, sulphur and carbendazim were selected for further studies. Effective concentrations (EC50 values) of the test fungicides that reduced Fusarium spore germination and fungal biomass by 50% were determined.Similarly, the EC50 for inhibiting fungal spore germination and reducing fungal biomass to 50% by Streptomyces sp. A6 and culture filtrate (CF) were also determined. Combining the EC50 dose of the culture and CF with test fungicides was found to be more effective for controlling Fusarium infection in C. cajan compared to the sum of the effects of the individual treatments. Such combined use ofbiocontrol agent with fungicides can reduce the dosage of toxic fungicides in agricultural fields, thereby reducing environmental risks. Tolerance and synergistic interaction of Streptomyces sp. A6 with frequently used fungicides suggested its potential in integrated pest management. To the best our knowledge, this is the first extensive study on integrated use of Streptomyces species with fungicides. Ó2011 Elsevier Ltd. All rights reserved.

1. Introduction Excessive use of pesticides in modern agriculture has led to several problems related to pollution, environmental degradation and emergence of resistant strains (Fox et al., 2007). Thus, in recent years, search for alternative methods that can minimize the use of toxic agrochemicals has been a focus. Integrated pest management (IPM) hasemerged as an eco-friendly and economic alternative to conventional use of chemical pesticides for controlling plant diseases in agricultural fields. IPM’s main feature is minimum use of synthetic pesticides and maximum reliance on natural regulatory mechanisms to keep pest populations below the level at which they can cause economic damage (Gray et al., 2009). One of the strategies used in IPM isintegrated use of biocontrol agents (BCAs) with pesticides. This approach reduces input of pesticides and, if appropriately chosen, provides better control of plant diseases than the chemical control. Several reports have indicated better control of

* Corresponding author. Tel.: þ91 265 2794396; fax: þ91 265 2792508. E-mail address: chhatparhs@yahoo.co.in (H.S. Chhatpar). 0261-2194/$ e see frontmatter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.03.015

plant diseases by integrated use of BCAs and pesticides (Kiewnick et al., 2001; Someya et al., 2007). The first requirement for any BCA to be used in IPM is its tolerance to the pesticides with which it is to be integrated. Secondly, it is necessary to determine the type of interaction between the BCA and pesticide...