Searching for Resistance to Eastern Filbert Blight: Hazelnuts from the Republic of Georgia the moderate climate of the Willamette Thomas Molnar1 and Michele Pisetta2 Valley is well suited to cultivars from 1Plant Biology and Pathology Department Europe. Rutgers University, 59 Dudley Road Our native American hazelnuts, C. New Brunswick, NJ 08901 americana, and its cousin the beaked [email protected] hazel, C. cornuta, are very resistant to 2Hazelnut Business Development - R&D EFB, due to having evolved alongside Ferrero S.p.A., Piazzale P. Ferrero 1 the fungus that causes the disease over 12051 ALBA (Cuneo), Italy millennia. While the American spe- [email protected] cies can be productive, their tiny, thick- shelled nuts do not compete with their European relative and for the most part azelnuts are a favorite nut crop gia), and chestnuts (Castanea spp.). have only been harvested from the wild of many NNGA members. The The top hazelnut producing country H for local consumption. Corylus ameri- plants are adapted to a wide range of in the world is Turkey, which gener- cana can be found growing over a wide climates and soils and their smaller ally produces more than 70 percent of area of eastern North America, and be- stature makes them suitable for back- the world’s crop (776,890 metric tons cause of its ability to harbor non-lethal yard orchards. They are easy to grow in 2007). Turkey is followed by Italy, EFB infections it acts as a reservoir of and harvest and require relatively little which produces around 17-20 percent inoculum to infect European hazelnuts in terms of pesticides or other chemical of the total, and then the U.S., which planted across its range. Fortunately, it inputs to produce tasty crops of nuts. produces less than five percent. Other also acts as a pool of genetic resources Currently, there is renewed interest in producing countries include Spain, useful for breeding EFB resistant, cold- growing them for personal consump- Georgia, Azerbaijan, Iran, France, hardy hybrid hazels, as demonstrated tion, as well as for large-scale produc- Greece, Russia and China (FaoStat, by the early successes of J.F. Jones, tion across much of the eastern U.S. 2009). G.H. Slate, C. Weschcke and others and southern Canada. There are now As many NNGA members already when crossing C. americana with culti- hazelnut breeding programs located at know, a native fungal disease called vars of C. avellana (Crane et al., 1937; Oregon State University (OSU) and Eastern Filbert Blight (EFB), caused Weschcke, 1954; Slate, 1969; Rutter, Rutgers University, as well as hazelnut by Anisogramma anomala, makes most 1987). However, when C. americana research underway at the University of European hazelnut cultivars nearly im- is used as a parent in breeding, it takes Nebraska, Lincoln, Minnesota State possible to grow across much of North several generations (amounting to many University, the University of Guelph, America, the only continent where this decades) to recover EFB-resistant, and the Arbor Day Foundation. disease is found. The European ha- cold-hardy hybrid plants with nut quali- The European hazelnut, Corylus zelnut is very susceptible to EFB and ties and yields suitable for commercial avellana, is the most coveted of the the disease is blamed for why there production. For example, the early first Corylus genus because of its large, has been no commercial production generation hybrids developed by Slate, thin-shelled nuts. It is an economically of hazelnuts in the eastern U.S. in the while suitable for backyard produc- valuable crop, ranking fifth in world past. Conversely, commercial hazelnut tion, did not produce consistent yields tree nut production behind cashews production has thrived in the Pacific of high-quality kernels in the amounts (Anacardium occidentale), almonds Northwest, as EFB was not found in needed to support a commercially vi- (Prunus dulcis), walnuts (Juglans re- this region until relatively recently and 16 THE NUTSHELL, December 2009 able industry (Slate, 1961). Further the acreage of hazelnut orchards in the bazaars, road side stands, research sta- generations of breeding were needed. Willamette Valley is increasing for the tions and botanical gardens. Over 4,000 While work to develop advanced gen- first time in decades. The power of nuts were brought back to Rutgers, with eration C. avellana x C. americana systematic plant breeding is clearly vi- a comparable group brought back to hybrids continues at Oregon State sualized when comparing the poor nut OSU. From this collection, over 1,200 University, Rutgers University and at quality of ‘Gasaway’ with that of the seedlings were grown at Rutgers and several private nurseries, it will likely new excellent quality EFB resistant re- inoculated with spores of A. anomala. be a decade or more before a suitable leases. This breeding success at OSU, In less than four years, a large major- proven hybrid cultivar is released to the besides saving the U.S. hazelnut indus- ity of these plants quickly succumbed public for commercial production. try, provides much tangible evidence to to the disease. However, after several One way to speed development of demonstrate the genetic improvement more years of continued evaluation and EFB resistant commercial quality ha- potential of Corylus, a genus that has constant disease pressure in the field, zelnuts is to search for resistance within undergone very little breeding and con- we were successful in identifying a the European species itself. While in tains a great deal of genetic diversity. small number that were highly resistant general the species is highly suscep- This evidence greatly bolsters enthusi- (Molnar et al., 2007). To our surprise, tible, rare plants exist that are resistant asm to develop improved C. avellana several of these plants produced large to EFB, as demonstrated by the obso- and hybrid hazelnuts for colder regions nuts of relatively high quality repre- lete pollinizer C. avellana ‘Gasaway’. across North America. senting great improvement over those While ‘Gasaway’ produces low yields The identification of ‘Gasaway’ from ‘Gasaway’ (Fig. 1). of very tiny, poor quality nuts (mak- spurred the search for other resistant We are currently using our best re- ing it a less than ideal parent in terms C. avellana cultivars and selections to sistant Russian plants in controlled of nut characteristics), it was the first provide a diversity of resistance genes crosses with pollen from elite but EFB and only source of C. avellana resis- to combat EFB. Shawn Mehlenbacher susceptible hazelnuts from the OSU tance identified at a time when hazelnut and his team at OSU closely evalu- breeding program. Our goal is to con- production in Washington and Oregon ated much of the large Corylus germ- currently investigate how the resistance was being devastated by EFB after plasm collection at the USDA Clonal genes are transmitted to the next gener- its inadvertent introduction in the late Germplasm Repository in Corvallis, ation while also working towards rapid- 1960s. ‘Gasaway’ was shown to carry Oregon, as well as their own diverse ly developing new resistant plants with a dominant allele at a single locus that collections, for resistance to this dis- much improved nut quality. This work transmits EFB resistance to its progeny ease. By developing and using both was funded in part by a NNGA research (Mehlenbacher and Thompson, 1991). greenhouse and field inoculation tech- grant. We hope that by identifying and Simply stated, ‘Gasaway’ transmits a niques, they were successful in identi- using EFB resistant parents that have gene for EFB resistance to fifty-per- fying a number of plants that did not decent nut size and quality, crossed cent of its offspring. Due to its predict- succumb to EFB, with several repre- with parents having excellent nut qual- able inheritance, a concerted effort was senting improvements over ‘Gasaway’ ity from the OSU breeding program, we made at OSU to use ‘Gasaway’ and its in many respects (Coyne et al., 1998; will produce improved EFB-resistant offspring in controlled crosses to devel- Lunde et al., 2000; Chen et al., 2005 & offspring in a shorter period of time op improved EFB resistant C. avellana 2007). They are currently using the best compared to the work with ‘Gasaway’. cultivars. While EFB resistance was of these resistant plants in their breed- From our efforts, we now have over inherited in a simple manner, the poor ing program to develop future releases one thousand plants in the greenhouse nut quality of ‘Gasaway’ still required for the Oregon hazelnut industry. and field representing the first genera- several generations of breeding, equat- Following the successful approach tion of new hybrids from these Russian ing to over 30 years, to finally develop of OSU, in 2002 a trip was made to parents. We also have several thousand EFB resistant plants that produce high southern Russia and the Crimean pen- hybrid seeds in stratification from simi- yields and kernels of proper quality for insula of Ukraine to collect hazelnut lar crosses made in 2009 that will be commercial markets. Nevertheless, germplasm to search for additional germinated and grown at Rutgers, as the most recent OSU introductions sources of EFB resistance and other well as at OSU and the University of (‘Yamhill’ for the kernel market and traits needed for breeding efforts in the Nebraska, Lincoln. ‘Jefferson’ for the inshell market,) as U.S. This was the first time hazelnuts Based on the success of the Russian well as several new compatible polliniz- were collected from this region for collection, we recently initiated a new ers, can be credited for revitalizing the evaluation on such a large scale. Nuts project to identify resistant plants from hazelnut industry in Oregon. Currently, were collected from local markets and a different geographic location to add THE NUTSHELL, December 2009 17 cause most of the hazelnuts collected in Georgia were purposely selected from plants with above average to excellent nut quality, with many having round, well-filled kernels with a high ratio of kernel to shell.