Bloom and vegetative bud break phenology of unique eastern filbert blight resistant hazelnut germplasms grown in New Jersey
Creators: name: Bell, Patrick Connor
Publisher: name: No Publisher Supplied
Year: 2024

description: In the United States, European hazelnut (Corylus avellana) is cultivated primarily in the Willamette Valley of Oregon; however, there is interest in expanding existing production in the eastern US. The main limiting factors in both regions is the fungal pathogen Anisogramma anomala, which causes the disease eastern filbert blight (EFB). While EFB can be managed with fungicides, the associated costs and challenges of spraying large trees make genetic resistance preferable. In the first study, a seed-based germplasm collection was made in 2009 in the Republic of Georgia and 1,374 of the subsequent seedlings were planted at Rutgers University, New Brunswick, NJ. They were exposed to high EFB pressure, and after 10 years, while most trees succumbed to disease, a small percentage of the trees (n=57) were found to exhibit high levels of resistance and hold significant value for breeding. In the first study, the flowering phenology of 57 trees originating from the Republic of Georgia were documented in the winter seasons of 2021-22 (Year 1) and 2022-23 (Year 2) and compared to a control group of 7 known cultivars with previously documented phenology. Results showed significant variation across the individual trees in the Georgian collection. Overall, the collection of Georgian trees demonstrated a wide range of bloom phenology, with significant overlap between Georgian pollen shed and controls’ pistillate receptivity, and individuals can be separated into early, medium, and late blooming categories. These results are useful to breeders who would integrate these novel sources of EFB resistance into their program, while ensuring that female flower bloom time or pollen release will be similar to that of other selections or cultivars. In addition to novel C. avellana germplasm, hybrids between C. avellana and C. americana are resistant to EFB. In the second study, the flowering phenology of 72 Rutgers University interspecific hybrid breeding selections from 16 different full sibling progenies was documented. The study also included seven hybrid breeding selections from the Upper Midwest Hazelnut Development Initiative and seven C. avellana cultivars as controls. All trees were surveyed twice weekly in the winter seasons of 2021-2022 and 2022-2023, and the phenology of their female flowers, male flowers (catkins), and vegetative buds recorded. The main goal was to document variation in the bloom times of the interspecific hybrid germplasm to identify compatible bloom partners within the trees studied in support of future cultivar releases. Results showed significant variation among the plant material evaluated, with more than 6 weeks in some cases separating the earliest from the latest blooming breeding selections. The European hazelnut controls tended to bloom (pistillate and staminate) earlier than the interspecific hybrids, but there were many that had overlapping bloom times, demonstrating a wide and useful range of bloom dates present in the hybrid germplasm suggesting hybrid selections could be paired with each other as well as with existing commercial cultivars.