Hazelnut selection from Oregon State University with resistance to Eastern Filbert Blight (EFB). Late shedding pollenizer for 703.007.'Theta', tested as OSU 1001.008, resulted from a cross of OSU 561.184 x 'Delta' made in 1999. 'Theta' has incompatibility alleles S5 and S15; both are expressed in the pollen. The trees set many catkins, and pollen is shed very late in the season, a few days after 'Epsilon', 'Zeta' and 'Eta'. It is a suitable pollenizer for OSU 703.007 which we propose to release as new cultivar 'Jefferson'. The nuts are small and nearly round, and mature a few days later than 'Barcelona'. Kernel quality is acceptable for many uses.
The OSU hazelnut breeding program proposes the release of two selections as pollinizers. The proposed names are 'Eta' and 'Theta', which are the next letters in the Greek alphabet. Their release comes after the release of 'Gamma', Delta', 'Epsilon', and 'Zeta' in 2001. All six have complete resistance to eastern filbert blight (EFB). We propose the release of 'Eta' and 'Theta' as pollenizers for OSU 703.007, which we propose to release as a new EFB-resistant cultivar 'Jefferson' for the in-shell market.
Four EFB-resistant selections (VR4-31, VR11-27, VR20-11 and VR23-18) released in 1991 as pollenizers for 'Barcelona' (S1 S2), express incompatibility allele S3 in their pollen. In 2001, four additional pollenizers were released, following the release of 'Lewis' in 1997 and 'Clark' in 1999. Pollen of 'Gamma' (S2 S10) and 'Delta' (S1 S15) is compatible on female inflorescences of 'Lewis' (S3 S8), which are receptive in mid-season. Pollen of 'Epsilon' (S1 S4) and 'Zeta' (S1 S1) is compatible on females of 'Clark' (S3 S8), which are receptive very late in the season. We are proposing the release of OSU 703.007 (S1 S3) whose female inflorescences are receptive very late in the season. Of the eight pollenizers listed above, seven are incompatible on OSU 703.007. The only compatible pollenizer, 'Gamma', sheds its pollen too early in the season to be a dependable pollenizer for OSU 703.007, although in some years 'Gamma' pollen shed overlaps receptivity of the earliest females of OSU 703.007. The duration of pollen shed of 'Yamhill' better overlaps receptivity of early-emerging OSU 703.007 females, but its vigor is lower than ideal for a pollenizer in a high-density orchard. In fact, no available pollenizer or cultivar combines the EFB resistance, compatibility, and late pollen shed needed for use as pollenizers in 'Jefferson' orchards. We propose to release 'Eta' and 'Theta' to fill the need for EFB-resistant pollenizers that shed pollen very late in the season and are compatible on female inflorescences of 'Jefferson'.
The need for late-shedding pollinizers for 'Jefferson' is urgent, as large numbers of trees are currently being planted. The release of additional EFB-resistant pollinizers is also desirable because it will give Oregon's hazelnut growers more options when establishing new orchards. We anticipate release of several additional EFB-resistant cultivars in future years. 'Eta' and 'Theta' could be useful as pollenizers for them. Nut yield and quality are not primary concerns in the selection o pollinizers. In older orchards, pollinizers represent about 11% of the total number of trees. In recent years, 5.5% is more common, but nut yields often suffer because of insufficient pollination. The planting of three pollenizers that shed pollen a different times during the winter flowering season increases the likelihood that females of the main cultivar will be pollinated.
Shawn Mehlenbacher, Release notice for 'Theta,' 2009.