Growth promotion and induction of resistance in tomato plant against Xanthomonas euvesicatoria and Alternaria solani by Trichoderma spp. A.D.B. Fontenelle * , S.D. Guzzo, C.M.M. Lucon, R. Harakava Instituto Biológico, Centro de Pesquisa e Desenvolvimento de Sanidade Vegetal, Laboratório de Bioquímica Fitopatológica, CP 12,898, CEP 04010-970 São Paulo, SP, Brazil article info Article history: Received 26 April 2011 Received in revised form 27 July 2011 Accepted 31 July 2011 Keywords: Bacterial spot Early blight Biocontrol Systemic protection Gene sequencing abstract In tomato crop, the induction of resistance emerges as an important alternative for achieving the reduction of chemicals in disease control. This study aimed to evaluate the ability of 28 Trichoderma isolates to promote the growth of tomato seedlings and to induce systemic resistance (ISR) against Xanthomonas euvesicatoria and Alternaria solani, the causal agents of bacterial spot and early blight, respectively. Twelve isolates promoted the increase of plant dry matter mass (DMM) above 100%, showing the great potential of these strains. All isolates were able to colonize the root system of tomato plants. The plant growth-promoting isolates were further evaluated for potential elicitation of ISR. Treatment of the soil with all Trichoderma isolates provided protection in tomato plants from 24.13 to 95.94% against X. euvesicatoria and 30.69 to 95.23% against A. solani. The most efficient isolates in reducing the severity of bacterial spot and early blight were the isolates IB 28/07, IB 30/07, IB 37/01 and IB 28/07, IB 30/07 and IB 42/03, respectively. The effect of different time intervals between Trichoderma application and inoculation with pathogens in inducing systemic resistance in tomato plants was eval- uated for the isolate IB 28/07. IB 28/07 conferred protection against both diseases at all time intervals, confirming the ability of the isolate to reduce the severity of these diseases up to 21 days after treatment of tomato plants. In vitro assays revealed that all isolates of Trichoderma were able to degrade cellulose. Only the isolate IB 34/08 showed antagonistic activity against X. euvesicatoria and none caused reduction in the in vitro mycelial growth of A. solani. Trichoderma isolates were identified at species level by DNA sequencing. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The tomato is an important crop throughout the world and is one of the main generators of employment in rural activities. Bacterial spot and early blight caused respectively by the phyto- pathogens Xanthomonas euvesicatoria Doidge and Alternaria solani (Ellis and Martin) Sorauer are two of the most serious diseases affecting this crop. According to Howell (2007), induction of resistance is considered an important tool to enable the reduction of agricultural chemicals. Plants normally susceptible to a particular pathogen can mount defense reactions and display enhanced resistance to subsequent infections by the same or even unrelated pathogens as a result of prior exposure to pathogens and physical stress or in response to treatment with different products, elicitor molecules or microor- ganisms (Métraux, 2001; Montesano et al., 2003; Guzzo et al., 2009). This resistance, known as systemic acquired resistance (SAR) or induced systemic resistance (ISR), has been demonstrated in many plantepathogen interactions and can result in a long-term systemic protection against a broad range of pathogens (Hammerschmidt et al., 2001; Métraux, 2001). The signaling molecules salicylic acid (SA) (Clarke et al., 1998; Pieterse et al., 1998), jasmonic acid (JA) and ethylene (ET) are involved in a refined network defense, eventually leading to an arsenal of defense responses against invaders (Resende et al., 2007). Trichoderma is a hemibiotrophic fungus effective in reducing the severity of plant diseases trough several mechanisms, such as antagonism and mycoparasitism attacking or inhibiting the growth of plant pathogens directly or by inducing systemic and localized resistance in plants (Harman et al., 2004a; Alfano et al., 2007). According to Harman et al. (2004a) the activation process of broad spectrum systemic resistance by Trichoderma spp. begins with the colonization of plant roots by this fungus. Trichoderma isolates that are able to establish such interactions induce massive changes in the transcriptome and plant metabolism, which leads to the accu- mulation of antimicrobial compounds, providing resistance to * Corresponding author. Tel.: þ55 11 5549 0114; fax: þ55 11 50871793. E-mail address: andreafontenelle@gmail.com (A.D.B. Fontenelle). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.07.019 Crop Protection 30 (2011) 1492e1500