Origin

‘Tonda Pacifica’, tested as OSU 228.084, resulted from a controlled cross of ‘Tonda Gentile delle Langhe’ (Clone O-15) and OSU 23.024 made in 1981 by Maxine M. Thompson (Fig. 1). ‘Tonda Gentile delle Langhe’ is the most important cultivar in the Piedmont region of northern Italy, where the crisp texture and strong nutty aroma of the kernels make it favorite for use in chocolate products. OSU 23.024 is from a cross of ‘Barcelona’ × ‘Extra Ghiaghli’. ‘Barcelona’ is Oregon's leading cultivar (Mehlenbacher and Miller, 1989). ‘Extra Ghiaghli’, obtained as scions from Greece (Raptopolous and Kantartzis, 1961), is a clone of the important Turkish cultivar Tombul (Gökirmak et al., 2009). Seeds from the controlled cross were stratified and the resulting seedlings grown in the greenhouse during the summer of 1982. A total of 95 seedling trees from this progeny were planted in the field at the Smith Horticulture Research Farm in Corvallis in Oct. 1982. The designation OSU 228.084 indicates the row and tree location of the original seedling. The original tree of ‘Tonda Pacifica’ set its first crop of nuts in 1986 but the crop was light and the nuts were not harvested. Nuts were harvested and evaluated in each of the next 4 years. The original tree performed well and was propagated over several years by tie-off layerage of the suckers. The rooted layers were lined out in a nursery row in each growing season after layerage. The resulting trees were used to plant replicated trial plots in Corvallis in Spring 1991, 1994, and 1999. All three trials were randomized complete block designs that included several OSU selections as well as ‘Barcelona’ and other standard cultivars as checks. Five trees of each selection were planted in the 1991 trial, eight trees of each in the 1994 trial, and four trees of each in the 1999 trial. A single-bearing tree of ‘Tonda Pacifica’ was retained at the conclusion of the yield trials and has been evaluated in Corvallis annually since that time. Trees were also established and observed in two grower orchards in the Willamette Valley. ‘Tonda Pacifica’ performed well in the continental climate of Maribor, Slovenia (Solar and Štampar, 2009). The name ‘Tonda Pacifica’ (round from the Pacific) is similar to those of the leading Italian cultivars and should facilitate its adoption by farmers and processors. The name was suggested by Michele Pisetta of the Hazelnut Business Development branch of Ferrero SpA (Alba, Italy). ‘Pacifica’ indicates its origin at Oregon State University near the Pacific Ocean. ‘Pacifica’ also anticipates the planting of new orchards of this cultivar in Chile, also near the Pacific Ocean.

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Description

Tree size of ‘Tonda Pacifica’, based on trunk cross-sectional area 30 cm above the soil at the end of the seventh growing season, was 83% of ‘Barcelona’ in the first trial, 67% in the second, and 81% in the third trial (Table 1). Trees have a globose shape (Fig. 2) and should be easy to manage in a commercial orchard, although some pruning to allow sunlight to penetrate the canopy is recommended. Branches become pendulous in late summer as a result of the weight of the nuts, and nut clusters are often hidden under the leaves. The original seedling and trees in the yield trials were not precocious, but cumulative yields in the first five crops (third to seventh year) were good. Compared with the precocious ‘Lewis’ and ‘Clark’, trees of ‘Tonda Pacifica’ begin to bear nuts 1 year later. Cumulative yields of whole nuts per tree in the first trial were the same for ‘Tonda Pacifica’ and ‘Barcelona’, although trees of ‘Tonda Pacifica’ were smaller (Table 1). In the second and third trials, cumulative yields were slightly higher for ‘Tonda Pacifica’ than for ‘Barcelona’. Nut yield efficiency of ‘Tonda Pacifica’, which adjusts yield for differences in tree size, was 1.18, 1.59, and 1.26 times that of ‘Barcelona’ in the three trials. The slightly smaller tree size of ‘Tonda Pacifica’ will allow plantings at slightly higher density. Kernel percentage (the ratio of kernel weight to nut weight) for well-filled nuts is 47% to 48% for ‘Tonda Pacifica’ compared with 43% for ‘Barcelona’ (Table 2). Commercial handlers, who find that field-run ‘Barcelona’ nuts average 40% kernel, can expect field-run ‘Tonda Pacifica’ to average 44% kernel. Because of its higher kernel percentage, kernel yields per acre will be considerably higher for ‘Tonda Pacifica’ than for ‘Barcelona’.

Table 1.Nut yields, trunk cross-sectional area, yield efficiency, and bud mite ratings of ‘Tonda Pacifica’ in comparison with other hazelnut cultivars and selections in three hazelnut trials.

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Table 2.Nut weight, kernel weight, kernel percentage, fiber rating, pellicle removal rating, and frequency of good nuts and seven types of defects of ‘Tonda Pacifica’ in comparison with other cultivars and selections in three hazelnut trials.

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‘Tonda Pacifica’ nuts are borne in clusters of three to four in husks 75% to 100% longer than the nuts. Although the husks are rather long, they are slit down the side, and the nuts fall free at maturity. The nuts are ready to be harvested mechanically 7 to 10 d before ‘Barcelona’ and 10 to 14 d after ‘Tonda Gentile delle Langhe’. The earlier maturity is a significant improvement over ‘Barcelona’, because it allows harvest in advance of adverse weather.

‘Tonda Pacifica’ is well suited to the blanched kernel market, but nuts are too small for the in-shell market (Fig. 3). ‘Tonda Pacifica’ shells are light yellow, similar to ‘Tonda Gentile delle Langhe’. Raw kernels have a moderate amount of fiber attached to the pellicle. When lightly roasted (150 °C for 15 min) and rubbed, most of the pellicle is removed (Table 2). Thus, blanching scores for ‘Tonda Pacifica’ are better than ‘Barcelona’ and ‘Tonda Gentile delle Langhe’. Kernel flavor and texture have been rated as good to excellent by researchers at OSU and taste panels at Ferrero's Quality Assurance Laboratory in Alba, Italy. ‘Tonda Pacifica’ kernels are smaller than those of ‘Barcelona’ and the same size as ‘Tonda Gentile delle Langhe’. Kernels of many Turkish hazelnut cultivars are of a similar size. European buyers consider 11 to 13 mm to be the ideal kernel diameter for many chocolate products. ‘Tonda Pacifica’ kernels are in this range with high crop loads resulting in smaller kernel size.

‘Tonda Pacifica’ produces fewer blank nuts than ‘Barcelona’, and the total frequency of defects is lower (Table 2). When crop load is heavy, the ‘Tonda Pacifica’ kernels do not fully fill the shell, but most are marketable. The frequency of moldy kernels in ‘Tonda Pacifica’ is very low and comparable to ‘Barcelona’. ‘Tonda Pacifica’ shows a slight tendency toward alternate bearing. Growers who prune trees in the “on years” will see more consistent yields as well as improved kernel quality. Single trees of three Italian cultivars with high kernel quality were included in the 1999 trial, and two of them were included in the 1991 trial. ‘Tonda Pacifica’ has fewer defects than all of them. ‘Tonda Gentile delle Langhe’ has many blanks and brown stains, ‘Tonda di Giffoni’ has many moldy kernels, and ‘Tonda Romana’ kernels blanch poorly.

‘Tonda Pacifica’ has incompatibility alleles S₁ and S₂, the same as ‘Barcelona’. Both alleles are expressed in the stigmas, but only S₁ is expressed in the pollen because of dominance. ‘Tonda Pacifica’ sets many catkins, and they start to shed pollen slightly earlier than ‘Barcelona’. Female anthesis is also slightly earlier than ‘Barcelona’. Thus, recommended pollenizers are the early shedders ‘Gamma’ and ‘Segorbe’ and the midseason shedder ‘Hall's Giant’ in a ratio of 2:2:1 with 11% of the trees planted to pollenizers. Pollen of ‘Barcelona’, ‘Ennis’, and ‘Tonda di Giffoni’ is incompatible on females of ‘Tonda Pacifica’. Pollen of ‘Tonda Gentile delle Langhe’ is compatible but is shed too early to be effective. Leaf budbreak of ‘Tonda Pacifica’ is with ‘Lewis’, ≈1 week later than ‘Barcelona’.

The relative susceptibility of hazelnut cultivars and selections to eastern filbert blight (EFB) caused by the fungus Anisogramma anomala is quantified by exposure of potted trees under structures topped with diseased branches. Cankers are counted and measured 20 to 22 months after exposure. ‘Tonda Pacifica’ trees were exposed in 1993 and 1996 (Table 3). Both tests showed ‘Tonda Pacifica’ to be slightly more susceptible than the moderately resistant ‘Barcelona’. Although the difference is not statistically significant, the susceptibility precludes ‘Tonda Pacifica’ from being recommended for the Willamette Valley and other areas where Anisogramma anomala is present. Susceptibility to bacterial blight caused by Xanthomonas campestris pv. corylina has not been determined, although no trees have been lost to the disease in our trial plots. ‘Tonda Pacifica’ is expected to perform well in areas where EFB is absent, including Chile, Georgia, Italy, and France. As noted earlier, ‘Tonda Pacifica’ has performed well in Slovenia (Solar and Štampar, 2009).

Table 3.Susceptibility to eastern filbert blight as assessed by exposure of potted hazelnut trees in two years.

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‘Tonda Pacifica’ is moderately resistant to bud mite (primarily Phytoptus avellanae Nal.). Trees were rated during the winter months for frequency of blasted buds on a scale of 1 (none) to 5 (many) in the 1991 and 1999 trials. Average ratings are similar to the moderately resistant ‘Casina’ and ‘Lewis’, and thus chemical control should not be necessary to control this pest.

Layers root easily and abundantly and are easy to handle in the nursery. Layers are slightly less vigorous and smaller in height and caliper than those of ‘Barcelona’. In vitro cultures have been established, and tree numbers are being increased by micropropagation.

Availability

A U.S Plant Patent application was submitted for ‘Tonda Pacifica’. A licensing agreement with Viveros Nefuen (Hijuelas, Chile) grants them the exclusive right to propagate and sell trees of ‘Tonda Pacifica’ in South America. Nurseries interested in a license for other countries should contact Oregon State University. European Union regulations currently prohibit the direct importation of Corylus plants from North America because of the threat posed by EFB.