The carob tree is a dioecious species with some hermaphroditic forms. It is a thermophilous evergreen tree that is well adapted to areas with a low altitude in the Mediterranean basin. Carob is a leguminous tree but is unable to fix atmospheric nitrogen (Martins-Loução and Rodríguez-Barrueco, 1982). Carob beans and seeds are used for many purposes, including food, fodder, and for making industrial products such as gums, sugar, and alcohol (Batlle and Tous, 1997; Calixto and Cañellas, 1982; Winer, 1980). Currently, carob pods are also explored as material for the production of bioethanol (Barracosa et al., 2008). The tree is also used for shade, restoring vegetation, and erosion control (Carlson, 1986; Esbenshade and Wilson, 1986; National Academy of Sciences, 1979). The European Union (namely Spain, Italy, Portugal, Greece, and Cyprus) produces more than 70% of the world crop, currently estimated to be around 300,000 t of pods, with Spain being the largest producer (accounting for 100,000 t). The other 30% is produced mainly in Morocco, Turkey, Algeria, and Tunisia. Until the 1960s, the pulp of the carob pod (90% of fruit weight) was traditionally used for animal feed. In Europe, the most valued part of the carob pod is currently the seed (about 10% of fruit weight) for extraction of the gum (additive E-410), which has a galactomannan content of about 80%. Locust bean gum (LBG) is used as a stabilizer and thickening agent in the food industry (Batlle and Tous, 1997; Johnsen et al., 1988; Neukom, 1989; Spina, 1986). In recent decades, this use has fostered interest in carob cultivation (Tous and Ferguson, 1996). Commercial cultivars and wild types differ largely in terms of pulp production, seed yield, and LBG content (Crescimanno et al., 1988; Kalaitzakis et al., 1988; Sánchez-Capuchino et al., 1988; Tous et al., 2001, 2006). The main cultivars grown in orchards in Spain, and other traditional Mediterranean countries have a high pulp content and low seed yield and are consequently not suitable for the new industrial uses aimed at kernel production (Tous and Batlle, 1990).
Previous studies on carob cultivars have focused on genetic variability (Barracosa et al., 2008; Caruso et al., 2008; Makrem et al., 2006; Tous et al., 1992), fruit description (Albanell et al., 1996; Barbagallo et al., 1997; Barracosa et al., 2007; Batlle and Tous, 1997; Orphanos and Papaconstantinou, 1969; Russo and Polignano, 1996), and chemical composition (Binder et al., 1959; Caja et al., 1988; Davies et al., 1971; Marakis et al., 1988; Vardar et al., 1980), but there is very little information on the agronomical performance of carob cultivars (Tous and Batlle, 1990), which is why there is renewed interest in carob germplasm banks and cultivar trials. Comparative trials are designed to determine which cultivars are best suited to a particular area, but only a few studies have been published (Batlle and Tous, 1998; Coit, 1961, 1967; Tous et al., 2008).
The aim of this carob trial was to determine the performance of four female cultivars growing in a rain-fed orchard near the coast of Tarragona (northeastern Spain) to select the most promising cultivar for planting new orchards, especially focusing on seed content and pod production.
Albanell, E., Caja, G. & Plaixats, J. 1996 Characterization of carob fruits (Ceratonia siliqua L.) cultivated in Spain for agroindustrial use Intl. Tree Crops J. 9 1 9
Barbagallo, M.G., di Lorenzo, R., Meli, R. & Crescimanno, F.G. 1997 Characterization of carob germplasm (Ceratonia siliqua L.) in Sicily J. Hort. Sci. 72 537 543
Barracosa, P., Osorio, J. & Cravador, A. 2007 Evaluation of fruit and seed diversity and characterization of carob (Ceratonia siliqua L.) cultivars in Algarve region Scientia Hort. 114 250 257
Barracosa, P., Lima, M.B. & Cravador, A. 2008 Analysis of genetic diversity in Portuguese Ceratonia siliqua L. cultivars using RAPD and AFLP markers Scientia Hort. 118 189 199
Batlle, I. & Tous, J. 1997 The carob (Ceratonia siliqua L.). Promoting the conservation and use of underutilized and neglected crops 17. Inst. Plant Genet. Crop Plant Res., Gatersleben/Intl. Plant Genet. Resources Inst. (IPGRI) Rome
Caja, G., Albanell, E. & Casanova, R. 1988 Composición química en principios inmediatos de la pulpa de garrofas españolas 131 136 Proc. II Intl. Carob Symp Valencia, Spain
Caruso, M., La Malfa, S., Pavlicek, T., Frutos, D., Gentile, A. & Tribulato, E. 2008 Characterization and assessment of genetic diversity in cultivated and wild carob (Ceratonia siliqua L.) genotypes using AFLP markers J. Hort. Sci. Biotechnol. 83 177 182
Crescimanno, F.G., De Michelle, A., di Lorenzo, R., Occorso, G. & Raimondo, A. 1988 Aspetti morfologici e carpologici di cultivar di carrubo (Ceratonia siliqua) 169 181 Proc. II Intl. Carob Symp Valencia, Spain
El Ferchichi, H., Naghmouchi, S., Walker, D.J., Correal, E., Boussaid, M. & Khouja, M.L. 2008 Variability in the pod and seed parameters and nuclear DNA content of Tunisian populations of Ceratonia siliqua L Agrofor. Syst. 74 73 81
Goor, A.Y., R.J. Ticho, and Y.G. Garmi. 1958. The carob. Agr. Publ. Section. Ministry Agr., Tel Aviv, Israel (in Hebrew with English summary).
Johnsen, S., Bruun, P. & Okkala, P. 1988 Application of LBG in food and pet food systems 577 587 Proc. II Intl. Carob Symp Valencia, Spain
Kalaitzakis, J.K., Mitrakos, K. & Marakis, S. 1988 Carob tree varieties from Crete (Greece) 291 301 Proc. II Intl. Carob Symp Valencia, Spain
Makrem, A., Ben Fadhel, N., Khoudja, M.L. & Boussaid, M. 2006 Genetic diversity in Tunisian Ceratonia siliqua (Caesalpinioideae) natural populations Genet. Resources Crop Evol. 53 1501 1511
Marakis, S., Kalaitzakis, J.K. & Mitrakos, K. 1988 Criteria for recognizing carob tree varieties 558 566 Proc. II Intl. Carob Symp Valencia, Spain
Martins-Loução, M.A. & Rodríguez-Barrueco, C. 1982 Studies in nitrogenase activity of carob (Ceratonia siliqua L.) callus cultures associated with Rhizobium 671 672 Proc. V Intl. Congress Plant Tissue Culture Tokyo
Melgarejo, P. & Salazar, D.M. 2003 Tratado de fruticultura para zonas áridas y semiáridas (Vol. II): Algarrobo, granado y jinjolero A. Madrid Vicente and Mundi-Prensa Madrid, Spain
National Academy of Sciences 1979 Carob 109 116 Tropical legumes: Resources for the future National Academy of Sciences Washington, DC
Orphanos, P.I. & Papaconstantinou, J. 1969 The carob varieties of Cyprus. Tech. Bul. 5 Cyprus Agricultural Research Institute Nicosia, Cyprus
Russo, G. & Polignano, G.B. 1996 Variation of seed and fruit characters in Ceratonia siliqua L. cultivars Genet. Resources Crop Evol. 43 525 531
Sánchez-Capuchino, J.A., Salazar, D., García, S., Martínez, R. & Melgarejo, P. 1988 Tipificación morfológica de los algarrobos de la Comunidad Valenciana 69 78 Proc. II Intl. Carob Symp Valencia, Spain
Tous, J., Romero, A., Hermoso, J.F., Ninot, A. & Plana, J. 2008 Fruiting and kernel production characteristics of ten Mediterranean carob cultivars in northeastern Spain J. Amer. Pomol. Soc. 62 144 150
Tous, J., Batlle, I., Rallo, J. & Romero, A. 2001 Prospección de variedades de algarrobo en las islas Baleares Investigación Agraria: Producción i Protección Vegetal 16 187 203
Vardar, Y., Seçmen, Ö. & Öztürk, M. 1980 Some distributional problems and biological characteristics of Ceratonia in Turkey Portugaliae Acta Biologica (A) 16 1–4 75 86