ORIGINAL PAPER AM fungi and PGP pseudomonads increase flowering, fruit production, and vitamin content in strawberry grown at low nitrogen and phosphorus levels Elisa Bona & Guido Lingua & Paola Manassero & Simone Cantamessa & Francesco Marsano & Valeria Todeschini & Andrea Copetta & Giovanni D’Agostino & Nadia Massa & Lorena Avidano & Elisa Gamalero & Graziella Berta Received: 9 May 2014 /Accepted: 12 August 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract There is increasing interest in the quality of crops because of the implications concerning health, economic rev- enue, and food quality. Here we tested if inoculation with a mixture of arbuscular mycorrhizal fungi (AMF) and/or two strains of plant growth-promoting bacteria (PGPB), in condi- tions of reduced chemical inputs, affects the quality and yield of strawberry fruits. Fruit quality was measured by concentra- tions of soluble sugars, various organic acids, and two vita- mins (ascorbic and folic acid). Co-inoculation with the AMF and each of the two PGPB resulted in increased flower and fruit production, larger fruit size, and higher concentrations of sugars and ascorbic and folic acid in comparison with fruits of uninoculated plants. These results provide further evidence that rhizospheric microorganisms affect fruit crop quality and show that they do so even under conditions of reduced chem- ical fertilization and can thus be exploited for sustainable agriculture. Keywords Arbuscular mycorrhiza . Pseudomonas . Fruit quality . Strawberry . Plant growth-promoting bacteria Introduction Arbuscular mycorrhizal fungi (AMF) and plant growth- promoting bacteria (PGPB) interact with roots, improving plant growth and health (Glick 1995; Smith and Read 2008). In addition to ameliorating plant mineral nutrition, the arbuscular mycorrhizal (AM) symbiosis affects plant hormone biosynthesis and plant metabolism (Torelli et al. 2000; Bona et al. 2010, 2011; Cicatelli et al. 2012; Lingua et al. 2012; Baslam et al. 2013). Effects of the AM symbiosis are observed not only in colonized root systems but also in the aboveground part of plants (leaves, flowers, and fruits) (Guerrieri et al. 2004; Copetta et al. 2006; Lingua et al. 2012). In fruit crops, AMF colonization stimulates growth (Hrselova et al. 1989; Gryndler et al. 2002), enhances photosynthesis (Burkowska 2002), induces early flowering and fruiting (Lu and Koide 1994; Poulton et al. 2002; Guerrieri et al. 2004), and improves the quality of crop products (Castellanos-Morales et al. 2010; Copetta et al. 2010, 2011; Lingua et al. 2013). PGPB stimulate plant growth both directly, through the biosynthesis of plant hormones (auxins and cytokinins), the reduction of stress-ethylene produced by plants, the nitrogen fixation, and the phosphate solubilization, and indirectly, by their antagonistic activity against phytopathogenic microor- ganisms, due to the synthesis of siderophores, antibiotics, enzymes, and fungicidal molecules and to the niche competi- tion (Gamalero and Glick 2011). Rhizospheric interactions positively affect soil quality (Barea et al. 2002), provide highly valuable ecosystem ser- vices, and can be exploited in order to increase yield, reduce chemical inputs, and develop an efficient form of sustainable agriculture (Gianinazzi et al. 2010). Strawberry plants are cultivated in different parts of the world, including tropical, subtropical, and temperate areas. Strawberries are consumed Electronic supplementary material The online version of this article (doi:10.1007/s00572-014-0599-y) contains supplementary material, which is available to authorized users. E. Bona : G. Lingua : P. Manassero : S. Cantamessa : F. Marsano : V. Todeschini : A. Copetta : N. Massa : L. Avidano : E. Gamalero : G. Berta Dipartimento di Scienze e Innovazione Tecnologica—DISIT, Università del Piemonte Orientale “A. Avogadro”, Viale T. Michel 11, 15121 Alessandria (AL), Italy S. Cantamessa : A. Copetta : G. D’Agostino : E. Gamalero : G. Berta (*) Mybasol s.r.l., Via Gentilini 3, 15121 Alessandria (AL), Italy e-mail: graziella.berta@unipmn.it Mycorrhiza DOI 10.1007/s00572-014-0599-y