Hazelnut Pollenizers `Gamma', `Delta', `Epsilon', and `Zeta'

Abstract

‘Gamma’ has incompatibility alleles S 2 and S 10 , but only S 10 is expressed in the pollen because of dominance (Mehlenbacher, 1997a). The trees set many catkins, and pollen is shed in midseason, at about the same time as ‘Daviana’. The pollen-shedding period is short, and thus ‘Gamma’ should not be the sole pollenizer in an orchard. It is a suitable pollenizer for ‘Lewis’ (S 3 S 8 ) and ‘Barcelona’ (S 1 S 2 ), but sheds pollen too early for ‘Clark’ (S 3 S 8 ) and ‘Ennis’ (S 1 S 11 ). It is incompatible on its parent ‘Casina’ (S 10 S 21 ). Nuts and kernels resemble those of ‘Casina’ but are slightly larger (Table 1). Nut maturity is a few days before ‘Barcelona’, and about 80% of the nuts fall free of the husk at maturity. The frequency of moldy kernels is very low. The original seedling tree was vigorous and moderately productive. Bud mite ratings are intermediate. ‘Delta’ has incompatibility alleles S 1 and S 15 ; both are expressed in the pollen. The trees set many catkins, and shed copious amounts of pollen in late midseason with ‘Hall’s Giant’. It is a suitable pollenizer for ‘Lewis’ and for early-emerging females of ‘Clark’, but is incompatible on ‘Barcelona’, ‘Ennis’ (S 1 S 11 ), and ‘Willamette’ (S 1 S 3 ). The nuts are slightly larger than those of ‘Casina’ (Table 1) and mature a few days later than ‘Barcelona’. About 85% of the nuts fall free of the husk at maturity, while a few remain attached to the husk at the edge of the basal scar. The original seedling tree was ‘Gamma’, ‘Delta’, ‘Epsilon’ and ‘Zeta’ are four new hazelnut (Corylus avellana L.) pollenizer cultivars. They were released by the Oregon Agricultural Experiment Station in February 2002. They shed pollen at different times during the fl owering season, spanning the time that female infl orescences of most cultivars are receptive. They have complete resistance to eastern fi lbert blight caused by Anisogramma anomala (Peck) E. Muller. ‘Gamma’ and ‘Delta’ carry resistance from ‘Gasaway’, while ‘Epsilon’ and ‘Zeta’ carry resistance from ‘Zimmerman’. The traditional pollenizers ‘Daviana’ and ‘Butler’, and four selections (VR4-31, VR11-27, VR20-11, and VR23-18) previously released as pollenizers for ‘Barcelona’, express incompatibility allele S 3 in their pollen (Mehlenbacher and Thompson, 1991). Although compatible on ‘Barcelona’ females (S 1 S 2 ), their pollen is incompatible on females of recently released ‘Lewis’ and ‘Clark’ (both S 3 S 8 ) (Mehlenbacher et al., 2000, 2001). ‘Gamma’, ‘Delta’, ‘Epsilon’, and ‘Zeta’ provide growers with additional pollenizer options for recently released and standard cultivars.