37 Characterization of the Ornamental Value of Calibrachoa spp. Native to Argentina G. Facciuto, M.J. Pannunzio, M.A. Coviella, S. Soto and J.C. Hagiwara Instituto de Floricultura, INTA, Castelar Argentina M. Borja Fundación PROMIVA La Veguilla Spain Keywords: germplasm, breeding, pot plant, precociousness, photoperiod Abstract Germplasm from 38 accessions was characterised under greenhouse conditions during the autumn-winter period in the Institute of Floriculture, INTA Castelar, Argentina. Flowering precociousness was detected in C. calycina and C. linoides and one accession of C. linearis. Plant habit variability was observed, especially in C. linoides where erect, semierect and decumbent phenotypes could be found. Most of the Calibrachoa accessions showed sprouting capacity after pruning, with the exception of C. linoides and C. helianthemoides. Genotypes suitable for breeding pot plants were selected. INTRODUCTION Calibrachoa spp. La Llave & Lexarza is an American genus of the Solanaceae family having the center of diversity in southern Brasil (Stehmann and Semir, 1997). The genus has a high ornamental and economic value due to the breeding of many commercial varieties for pot plants and landscaping, since cv. Million Bells (Suntory) was introduced to the market. Historically Calibrachoa had been included in the Petunia Jussieu genus due to morphological similarities. Wijsman and Jong (1985) classified species belonging to the Petunia or the Calibrachoa genus by their different chromosome number (Petunia 2n=2x=14 and Calibrachoa 2n=2x=18), the last being predominantly subarbustive and perennial while those species belonging to the Petunia genus are mainly herbaceous and annual. The objective of this study was to characterise the ornamental value of the Calibrachoa collection of the Institute of Floriculture, especially searching for pheno- types with commercial valuable traits like compact shape, good pot cover, and precocious flowering. It is possible that many of the species or genotypes present in the Argentine flora have not been used yet in the Calibrachoa breeding programmes. MATERIALS AND METHODS Germplasm from 38 accessions was characterised under greenhouse conditions during the autumn and winter period (minimum temperature of 15ºC) in the Institute of Floriculture, INTA Castelar, Argentina (34°36’ south latitude, 58°40’ west longitude). Accessions tested and place of collection are shown in Table 1. Accessions were propagated by 4 cm cuttings and cultivated in a mixture of peat, perlite and vermiculite (1:1:1). Rooted cuttings were transplanted to plastic pots (13 cm diameter) filled with substrate composed by peat, river waste, soil, pine leaves and rice dusk (4:1:1:2:0.25) and cultivated in greenhouse during autumn (March to September). By the end of September plants were pruned and transplanted to 17 cm diameter plastic pots. Sprouting capacity was recorded. The descriptor DUS of UPOV (www.upov.int) with 26 characters was used for morphological characterisation. Some additional characteristics of ornamental interest were recorded, such as: number of flowers in full bloom, pot cover after three months culture and at full bloom. For the evaluation of pot cover, photos were taken of each plant and data was processed using the Image Tool Program. Ten plants were evaluated for each accession. Proc. XXII nd Intl. Eucarpia Symp. (Sect. Ornamentals) on Breeding for Beauty Eds. A. Mercuri and T. Schiva Acta Hort. 714, ISHS 2006