Analele Universit ăţii din Oradea - Fascicula Biologie Tom. XIX, Issue: 1, 2012, pp. 48-54 48 THE EFFECT OF THE IN VITRO ENVIRONMENTAL CONDITION ON ORGANOGENETIC POTENTIAL OF TWO INTERGENERIC HYBRIDS Fragaria X Potentilla Anca Nicoleta SUTAN * , Aurel POPESCU * , Valentina ISAC ** * University of Piteşti, Faculty of Sciences, Department of Natural Sciences, Piteşti, Romania ** Research Institute for Fruit Growing, Piteşti, Romania Corresponding author: Anca Nicoleta Sutan, University of Piteşti, Faculty of Sciences, Department of Biology and Horticulture, 1 Târgu din Vale, 110040 Piteşti, Romania, phone: 0040348453100, fax: 0040348453123, e-mail: ancasutan@yahoo.com Abstract. Using liquid culture medium provided with filter-paper bridges, a simple plant regeneration system via organogenesis from leaf and petiole explants of two intergeneric hybrids Fragaria x Potentilla, named ‘Pink Panda’ and ‘Serenata’, has been developed. The regeneration capacity of the explants was influenced by the light condition and plant growth regulators concentration. Dark incubation during the first 6 weeks, followed by the transfer of the cultures under a photoperiod of 16 hours light/8 hours darkness, at a relatively low intensity of light was the most effective condition to successfully induce shoots regeneration in both intergeneric hybrids. The pretreatment darkness of 21 days, followed by the cultures transferring under a photoperiod of 16 hours light/8 hours darkness and a light intensity of about 40 µmol m -2 s -1 has been associated with an incapacity of calluses to form adventitious buds, regardless of the explant type or hormonal balance. Optimal shoot regeneration was obtained with BAP in a concentration of 3.0 mg/l, in combination with 1.0 mg/l IBA, added to modified Murashige-Skoog medium. Shoot regeneration frequency were as high as 54.66% in ‘Serenata’ genotype and 43.33% in ‘Pink Panda’ genotype. Keywords: ornamental strawberry, liquid culture, callus, organogenesis, shoot regeneration INTRODUCTION The strawberry is among the few species characterized by a high rate of replacement of varieties and assortments, closely related to the consummer demands, the extensive breeding activity offering the possibility of growing strawberry from the temperate areas to the subtropical regions and cold regions in the northern hemisphere. Generally, the breeding objectives for the cultivated strawberry are the identification of highly valuable phenotypes, their hybridization and selection of progenies which can be either released as new varieties or used as genitors in the next breeding generation. However, as a consequence of the limited genetic diversity observed within the Fragaria x ananassa germplasm [13], it is considered that the obtention of some favorable combinations of traits into the new strawberry varieties will be possible only by the increase of the number of genitors belonging to the exotic germplasm [14], or tho the related genera. If for long time the intergeneric hybridization was considered impossible to use in the case of species with different ploidy level [11], the advances from the last two decades in manipulating the ploidy and the optimization of techniques for hybridization and rescue of zygotic embryos resulted from distant hybridizations, have determined an almost a radical reconsideration of the practical use of this method for the genetic improvement of cultivated strawberry. The intergeneric hybrids Fragaria x Potentilla, known as ornamental strawberies, are harmoniously combined with the exigences of the present, and have an increasing commercial value. Thus, the production in a short time of the required amount of planting material, guaranteed for authenticity and biological value, is essential. Moreover, the hybridization of ornamental species is constantly seeking for new technologies, which could help substantially the reduction of production costs, enhancement of the quality of resulted product, as well as the diversification of varieties and assortments. In this way, the increase of productivity in the new obtained variety is achieved by improving the desired traits, such as size, color and flavor of fruits, together a prolonged period of flowering and fruiting. Thus, micropropagation represent a system generally accepted for the large scale propagation of the strawberry varieties, under conditions of the use with maximum attention of an well established procedure. Incontestably, there is a fact that Fragaria x ananassa was one of the pioneer species in applying the in vitro culture techniques on large scale [28]. In strawberry, meristem culture, used as a method for micropropagation, has already a history of four decades. Concerning the induction of adventitious shoot formation, from the first attempt to induce callus formation from meristems and regenerate plants [26], the range of explant types tested has considerably enlarged, including leaf, petiole, root, immature embryos, cotyledons, anthers, receptacle, petal, etc. Efficient protocols for adventitious shoot regeneration from calli cultivated in vitro have been established only in the last two decades. The experimental results have shown that, in general, the capacity to form callus and the regenerative response are influenced by the explant type, source of explants, type and concentration of growth regulators, culture conditions, and genotype. Very often, the conditions standardized for a variety are not optimal for others. This suggests possibly the interaction between the levels of endogenous and exogenous hormones in the expression of regenerative response. As the existence of a strong interaction between the type of explant, growth regulators and culture conditions became obvious, all these variables must be taken into consideration simultaneously in elaboration of a regeneration system for a commercial strawberry variety.