Postharvest Biology and Technology 85 (2013) 196–202 Contents lists available at ScienceDirect Postharvest Biology and Technology journal h om epa ge : www.elsevier.com/locate/postharvbio Rhodosporidium paludigenum induces resistance and defense-related responses against Penicillium digitatum in citrus fruit Laifeng Lu a,b , Huangping Lu a,b , Changqing Wu c , Weiwen Fang d , Chen Yu a,b , Changzhou Ye a , Yibing Shi a , Ting Yu a,b,∗ , Xiaodong Zheng a,b,∗∗ a Department of Food Science and Nutrition, Zhejiang University, Hangzhou 310058, People’s Republic of China b Fuli Institute of Food Science, Zhejiang University, Hangzhou 310058, People’s Republic of China c Department of Animal and Food Sciences, University of Delaware, Newark, DE 19716-2150, USA d Chun’an County Agriculture Bureau, Chun’an 311700, People’s Republic of China a r t i c l e i n f o Article history: Received 19 July 2012 Accepted 11 June 2013 Keywords: Rhodosporidium paludigenum Penicillium digitatum Citrus fruit Induced resistance Postharvest biological control a b s t r a c t Induced disease resistance against plant pathogens is a promising non-fungicidal decay control strategy. In this study, a potential biocontrol yeast, Rhodosporidium paludigenum, was investigated for its induction of disease resistance against Penicillium digitatum in citrus fruit. The results showed that R. paludigenum is the most effective yeast among three selected yeasts in stimulating the resistance of citrus fruit to green mold. When R. paludigenum was applied 48–72 h before inoculation with P. digitatum, disease incidence and disease severity in citrus fruit significantly decreased. Application of R. paludigenum at concentrations of 1 × 10 8 and 1 × 10 9 cells mL -1 respectively resulted in 49.6% and 52.5% reductions in the percentage of infections. Induction of resistance to P. digitatum by R. paludigenum treatment significantly enhanced the activities of defense-related enzymes, including ˇ-1,3-glucanase, phenylalanine ammonia-lyase, perox- idase, and polyphenoloxidase, which may be an important mechanism by which the biocontrol yeast reduces the fungal disease of citrus fruit caused by P. digitatum. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Citrus reticulata Blanco cv. Ponkan is a well-known citrus fruit grown in China and Japan. Losses caused by various postharvest pathogens account for nearly 50% of the total wastage in citrus fruit, which occur at different stages in the farm and after harvest during marketing (Ladaniya, 2008). Penicillium digitatum (Pers.:Fr.) Sacc., the causal agent of green mold, is responsible for major posthar- vest losses of citrus fruit and accounts for up to 60–80% of the total fungal decay during fruit storage (Ballester et al., 2011). Fungicides such as thiabendazole, imazalil, and sodium o-phenulphenate are used worldwide to minimize the postharvest decay of citrus fruits (Schirra et al., 2011). However, with increasing concerns regarding the dietary and environmental safety of fungicides and the occur- rence of fungicide resistance in pathogens, developing safer and ∗ Corresponding author at: Zhejiang University, No. 866 Yuhangtang Road, Hangzhou 310058, People’s Republic of China. Tel.: +86 571 88982398; fax: +86 571 88982191. ∗∗ Corresponding author at: Zhejiang University, No. 866 Yuhangtang Road, Hangzhou 310058, People’s Republic of China. Tel.: +86 571 88982861; fax: +86 571 88982191. E-mail addresses: yuting@zju.edu.cn (T. Yu), xdzheng@zju.edu.cn (X. Zheng). more eco-friendly alternatives are necessary to control postharvest decay (Sharma et al., 2009; Smilanick et al., 2005). Induced resistance against plant pathogens is a very promis- ing non-fungicidal decay control strategy, providing long-term systemic resistance to a broad spectrum of pathogens and pests (Walling, 2001). Induced resistance can be achieved by the appli- cation of physical (Arcas et al., 2000; Liu et al., 2010), chemical (Venditti et al., 2005; Zhang et al., 2011), and biological treatments (Droby et al., 2002; El Ghaouth et al., 2003; Nantawanit et al., 2010). In the postharvest fruit-yeast biocontrol system, disease resistance can be stimulated by Candida famata and Candida oleophila in cit- rus fruit (Krihak et al., 1996; Droby et al., 2002), by Aureobasidium pullulans and Candida saitoana in apple fruit (Ippolito et al., 2000; El Ghaouth et al., 2003), by Cryptococcus laurentii in jujube fruit (Tian et al., 2007), and by Pichia guilliermondii in chili fruit (Nantawanit et al., 2010). However, the mechanism by which yeasts induce resistance remains largely unknown because of the complex inter- actions among host, pathogen, and antagonist (Droby et al., 2009). Previous studies indicated that Rhodosporidium paludigenum Fell & Tallman can significantly inhibit various fungal diseases of harvested fruits (Wang et al., 2008, 2010a,b). However, further study on the use of this biocontrol yeast to induce fruit resistance has yet to be conducted, and the mechanism by which R. paludi- genum suppresses diseases is incompletely understood. Thus, this study was undertaken to determine whether or not R. paludigenum 0925-5214/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.postharvbio.2013.06.014