Corylus avellana L. (Betulaceae) represents an economically important crop in the European Community, particularly in the biogeographic Mediterranean basin (http://www.fao.org/). Hazelnuts are produced principally in Turkey, Italy, the United States, and Spain (550,000, 110,000, 25,000, 18,000± tons, respectively, per year) followed by France, Greece, and Portugal. Approximately 90% of production is shelled and sold as kernels, whereas the remaining 10% goes to fresh consumption. Interest in this species is also the result of its excellent nutritional and nutraceutical properties (Phillips et al., 2005; Sivakumar and Bacchetta, 2006; Sivakumar et al., 2005). Moreover, in the typical cultivation areas, traditions and cultural identity are strongly tied to hazelnut production, whereas the latter also contributes to a suitable use and recovery of marginal land. Even if, in some regions, this crop is not the major agricultural resource, it nevertheless represents an interesting source of income for the local sustainable production system and a precious food for traditional local use. Italy, the world's second largest producer, boasts several traditional cultivars, which are mainly cultivated in Campania, Latium, Piedmont, and Sicily with a large number of local genotypes (Bacchetta et al., 2005). In the last few years, some of the major cultivars (Tonda Romana from Latium, Tonda di Giffoni from Campania, and Tonda delle Langhe from Piedmont) obtained the European Community quality stamp for their quality and traditional peculiarity. Moreover, these cultivars are often introduced into other countries to increase their range of cultivated genotypes, because they are easily adaptable and productive.
Traditional hazelnut propagation in Italy is mostly carried out by farmers themselves using the suckers of “vigorous mother plants” selected in orchards. Without certified materials, it is possible to spread diseases widely (Scortichini, 2002) or reproduce materials of unknown origin. The use of biotechnologies such as micropropagation promotes the production of healthy and true-to-type materials (Nas et al., 2004), improving the economic value of the crop. Using micropropagation, the breeding program could be accelerated by a rapid distribution of standard or new cultivars.
One of the main limitations of hazelnut in vitro propagation from mature tissues is the high degree of endogenous contamination (Diaz-Sala et al., 1990; Nas and Read, 2004; Reed et al., 1998), which makes the establishment of the culture a very laborious and time-consuming phase.
Moreover, several media formulations have been proposed for optimizing shoot multiplication and elongation in the main hazelnut cultivars (Andres et al., 2002; Damiano et al., 2005; Messeguer and Mele, 1987; Yu and Reed, 1993). However, when the standardized protocol was applied to local and minor cultivars, the results were contradictory and some difficulties in shoot growth were observed (Bacchetta et al., 2005). Nas and Read (2004) recently proposed a novel method for medium formulation based on the concept that nut nutritional reserves are able to guarantee suitable conditions for seedlings as well as for in vitro shoots. However, there are physiological differences between seed tissues and the somatic parts of plants. Moreover, the concentration of essential nutritional compounds present in seeds can be too high or toxic for somatic tissues.
In the present work, this approach was slightly revised and the mineral hazelnut medium formulation was optimized by using the differences in seed macro- and microelements of two species, one of them well adapted to in vitro conditions.
Because the success of micropropagation is the result of a combination of many factors, including tissue type and hormone requirement, the effect of the physiological stages of the initial explants on culture establishment and the influence of zeatin or 6-benzylamminopurine (BA) concentrations in stimulating shoot proliferation were evaluated.
These goals met the objectives of research project SCRIGNO, supported by the Ministry of Industry and Scientific Research, aimed at evaluating local agrobiodiversity for “typical, traditional” products and meet those of the AGRI GEN RES 068 Safenut EU program covering the characterization, conservation, and utilization of genetic resources.
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