Induction of PR proteins and resistance by the biocontrol agent Clonostachys rosea in wheat plants infected with Fusarium culmorum Roberta Roberti a , AnnaRita Veronesi a , Augusto Cesari a , Annunziata Cascone b , Iris Di Berardino b , Laura Bertini b , Carla Caruso b, * a Dipartimento di Protezione e Valorizzazione Agroalimentare, Universita ` di Bologna, Viale Fanin 46, Bologna 40127, Italy b Dipartimento di Agrobiologia e Agrochimica, Universita ` della Tuscia, Via S. Camillo De Lellis, Viterbo 01100, Italy 1. Introduction Plant diseases play a direct role in the destruction of natural resources in agriculture. Not only growing crops but also stored fruits are prey to fungal infections, soil borne pathogens being the most aggressive [1]. The use of microorganisms that antagonize plant pathogens is risk-free when it results in enhancement of resident antagonists. Moreover, the combination of such biological control agents (BCAs) with reduced levels of fungicide (integrated control) promotes a degree of disease suppression similar to that achieved with full fungicide treatment [2]. In the past few years, Trichoderma spp., the most common saprophytic fungi in the rhizosphere, has received considerable attention as potential biocontrol agent for a number of soil borne pathogens [3]. The mechanisms by which Trichoderma isolates control pathogenic populations in the rhizosphere have been extensively studied. In most cases, the antagonistic process relies on the production of antibiotics [4] and/or hydrolytic enzymes [5] associated with possible competition for nutrients in the rhizo- sphere [6]. In the last years, several Clonostachys rosea (syn Gliocladium roseum; teleomorph Bionectria ochroleuca) strains proved to be effective bioagents against either soil borne or seed borne pathogens [7]. The fungus C. rosea (CR) is a common worldwide saprophyte with destructive effect against several plant patho- genic fungi [8]. In fact, a growing number of reports demonstrate that CR strains have antagonistic features against a wide variety of phytopathogenic fungi [8–10]. The modes of action of C. rosea as BCA are less understood than that of Trichoderma spp.; nevertheless mycoparasitism, substrate competition, enzymatic activity and induced resistance are thought to play a significative role [8,11,12]. Moreover, production of secondary metabolites may also exert an antibiotic effect as known from other biocontrol fungi [10,13]. C. rosea has been found in association with many different parts of living organisms as well as dead plant material indicating a high versatile ecological fitness [8]. A study conducted by Lubeck et al. Plant Science 175 (2008) 339–347 ARTICLE INFO Article history: Received 8 January 2008 Received in revised form 19 March 2008 Accepted 13 May 2008 Available online 18 May 2008 Keywords: Biocontrol agent Clonostachys rosea Fusarium culmorum Phytopathogen PR proteins Resistance induction ABSTRACT Clonostachys rosea (CR) is a common worldwide saprophyte with destructive effect against several plant pathogenic fungi showing antagonistic features against a wide variety of pathogens. We recently isolated a strain of C. rosea, named CR47, from wheat crown infected with Fusarium culmorum (FC); this strain proved to be effective against Fusarium seed borne diseases of cereals under field condition. In this paper the function of C. rosea applied as seed treatment on wheat seedling growth was investigated. In addition, we investigated the expression pattern of peroxidases and chitinases as well as PR4 proteins following both CR treatments of seeds and FC infection and also in the three-component system pathogen– antagonist–wheat. Several chitinase isoforms were induced by CR-treatment both in coleoptiles and roots, whereas some peroxidase isoforms were induced only in the presence of both antagonist and pathogen. In the latter case, it seems that CR-treatment by itself promotes plant growth and reduces the peroxidase expression, while enhances some chitinase isoforms probably involved in cell wall disruption. Moreover, both the antagonist and the pathogen studied induced PR4 protein expression, which probably exerts its role on the invading microorganisms by a translation-inhibitory process that could be ascribed to their ribonuclease activity. ß 2008 Elsevier Ireland Ltd. All rights reserved. * Corresponding author. Tel.: +39 0761357330; fax: +39 0761357242. E-mail address: caruso@unitus.it (C. Caruso). Abbreviations: BCA, biocontrol agent; CR, Clonostachys rosea; DAT, days after treatment; FC, Fusarium culmorum; PR, pathogenesis related. Contents lists available at ScienceDirect Plant Science journal homepage: www.elsevier.com/locate/plantsci 0168-9452/$ – see front matter ß 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2008.05.003