ORIGINAL PAPER ROLC strawberry plant adaptability, productivity, and tolerance to soil-borne disease and mycorrhizal interactions L. Landi Æ F. Capocasa Æ E. Costantini Æ B. Mezzetti Received: 25 October 2008 / Accepted: 5 May 2009 / Published online: 23 May 2009 Ó Springer Science+Business Media B.V. 2009 Abstract The potential to improve strawberry cul- tivation was assessed regarding the use the rolC genes from Agrobacterium rhizogenes that can confer higher levels of free cytokinins. Strawberry (cv. Calypso) rolC lines were produced by genetic transformation of Agrobacterium tumefaciens. Yield and fruit quality of the control and transgenic lines were measured under open-field conditions. The effects of the transgenic rolC lines depended on gene copy number: rolC lines with one (Line A) or two gene (Line B) copies showed 30% greater yields than controls, due to 20% more fruit per plant and an increased fruit weight. Line A also differed in terms of the highest fruit quality, due to 10.5% increased soluble solids and 12.7% higher acidity. Moreover, cv. Calypso rolC lines A and B had increased tolerance to greenhouse infection by Phytophthora cactorum. Conversely, for all of these characters, Line F (five rolC copies) was not significantly different from the control line. The same lines were also used to examine their symbiosis with root arbuscular mycorrhizal fungi (AMF) using vital and non-vital staining of roots collected at different stages of plant growth. Control and rolC plants showed similar intensities of AMF infection according to plant phenology and/or physiology. Furthermore, possible horizontal gene transfer of the rolC gene was tested for the AMF spores by PCR, with all AMF samples negative using rolC primers. The use of the rolC gene should be considered for the improvements provided in productivity, fruit quality and disease resistance of cultivated strawberry that show no effects on soil microorganisms. Keywords F. x ananassa  A. rhizogenes  Genetic transformation  Plant phenotype  P. cactorum  Mycorrhizae Introduction The rol genes, and in particular rolC, have been used to improve important characteristics of horticultural crops. The insertion of rolC from Agrobacterium rhizogenes in ornamental plants, such as carnation and petunia, led to the expression of advantageous traits (Casanova et al. 2003), i.e., increased branch- ing, better rooting of stem cuttings, and reduction in time to flowering (Winefield et al. 1999; Zuker et al. 2001). Transgene expression of the rolC gene increased the rooting rate of trifoliate orange and Japanese persimmon cuttings, enhancing their Electronic supplementary material The online version of this article (doi:10.1007/s11248-009-9279-7) contains supplementary material, which is available to authorized users. L. Landi  F. Capocasa  E. Costantini  B. Mezzetti (&) Dipartimento di Scienze Ambientali e delle Produzioni Vegetali, Marche Polytechnic University, Via Brecce Bianche, 60131 Ancona, Italy e-mail: b.mezzetti@univpm.it 123 Transgenic Res (2009) 18:933–942 DOI 10.1007/s11248-009-9279-7