EVALUATION AND UTILIZATION OF C. avellana GENETIC RESOURCES TO SELECT CLONES FOR HAZELNUT VARIETAL TURNOVER IN THE LATIUM REGION (ITALY).

In the Latium Region (Italy) the hazelnut orchards cover about 18 000 ha of land and 90 % of the hazelnut crop production is obtained from the cv 'Tonda Gentile Romana' ('TGR'). This is an extreme case of narrow genetic base for a nut crop in Italy and vulnerability to epidemic biotic stress and abiotic factors will be expected for the hazelnut orchards. Therefore a research aimed to the enlargement of the genetic base of the hazelnut crop in Latium Region was undertaken. The attention was focused on the identification of promising entries that could be proposed for the varietal turnover and/or as new pollinizer of 'TGR' in the hazelnut producing areas of Viterbo province districts of the Latium Region.

A field collection composed by 59 entries grown in the major hazelnut producing districts of the world was established at Vico Matrino (Viterbo, Italy) in the framework of a cooperative research between ARSIAL-Viterbo and Istituto Sperimentale per la Frutticoltura-Rome. The field collection was evaluated from 1991 to 1995 for nut yield per plant, husk and nut morphology traits. The ranges of means over entries suggested the presence of extensive variation among accessions for all the traits studied. 'Tonda di Giffoni' ('TG'), 'S. Giovanni' ('SG'), and 'Comune di Sicilia' ('CS'), were the highest yielding entries of the collections when mean nut yield per plot (3 plants) over the years were compared. 'Tonda Gentile Romana' ('TGR') and 'Tonda Gentile delle Langhe' ('TGL') produced about 50 % and 77 %, respectively, less nuts per plant then 'TG'. The superiority of the accessions from Campania ('TG' and 'SG') and from Sicily ('CS') may be due in part to their wider adaptability and strong plant vigour (although 'CS' is not as vigorous as 'SG'). It should be emphasized the large differences in yield potential showed by 'TG', 'SG', and 'CS', compared to the rest of the entries. As matter of fact, the fourth ranking entry for yield per plot was 'Trenet', which showed about one third less nut yield than the higher ranking entries. However 50 accessions produced less than 'TGR' indicating that this entry is still among the good performing hazelnut varieties. 'TG' and 'CS' showed round shape and 'SG' an elongated shape as deduced by the high (1.5) nut lenght/nut width ratio. Other authors have reported that 'TG' has incompatibility alleles different from those of 'TGR' and the kernels contained an higher proportion of antioxidant (tocoferol) and were easily blanched than 'TGR'. Therefore, 'Tonda di Giffoni' is suggested as cultivar for hazelnut varietal turnover and/or as pollinizer of 'TGR' in the hazelnut producing areas of Viterbo district although ‘CS’ and ‘SG’ entries should also be introduced in small scale varietal turnover trials.