Location: Horticultural Crops Research2011 Annual Report
1a. Objectives (from AD-416)
Develop improved germplasm and cultivars of hazelnut with resistance to eastern filbert blight and suitability for the kernel market.
1b. Approach (from AD-416)
The general approach relies upon plant breeding complemented by marker-assisted selection. Two strategies are proposed, one utilizing a known dominant gene (from 'Gasaway') for resistance to eastern filbert blight (EFB), with the second strategy seeking and exploiting other sources of EFB resistance. For the first strategy, seedlings from crosses will be screened initially for the presence of the 'Gasaway' gene using DNA markers that flank the resistance gene. Seedlings with the DNA markers will be planted in the field, and their nuts will be evaluated as trees begin to bear. Selections with desirable nut and kernel traits will then be evaluated for EFB resistance in the greenhouse and in the field. In the second strategy, germplasm lacking the 'Gasaway' resistance gene will be evaluated for susceptibility to EFB. Germplasm exhibiting resistance will be incorporated into the breeding program as it is discovered. DNA markers for each new resistance gene will be identified for use in marker-assisted selection. The linkage map for hazelnut will be continually enhanced by adding new simple sequence repeat (SSR) loci. Dominant EFB resistance genes will be assigned to linkage groups based on linkage with mapped SSR loci. A draft genome of the Oregon isolate of the fungal pathogen will be obtained using two next-generation DNA sequencing approaches (Illumina and Roche 454). SSR and other types of markers will be developed from the draft sequence and used to distinguish fungal isolates.
3. Progress Report
New cultivars from the Oregon State University (OSU) hazelnut breeding program are being propagated by nurseries and planted by growers. These cultivars combine the eastern filbert blight (EFB) resistance allele from 'Gasaway' and desirable nut characteristics, precocity and yield. The industry is expanding as ~3000 acres of new orchards are planted to OSU cultivars each year; this represents a 10% increase in acreage in each of the past three years. 'Jefferson' with large nut size was released as an EFB-resistant replacement for 'Barcelona'. It is being widely planted in the Willamette Valley along with late-shedding resistant pollinizers 'Eta' and 'Theta'. 'Yamhill', a high-yielding EFB-resistant cultivar for the kernel market, is being planted to a lesser extent. Several buyers have expressed an interest in 'Yamhill' kernels. In vitro cultures of several promising selections are being established and maintained at the USDA Repository. The OSU breeding program continues to make crosses, and plants ~4,500 seedlings per year. Dozens of advanced selections are being evaluated in replicated trials. 'Jefferson' and 'Yamhill' carry a dominant allele from 'Gasaway', but other sources of resistance are used in the breeding program to ensure durable resistance to this disease. 'Gasaway' resistance maps to linkage group six (LG6). Resistance from the Spanish cultivar 'Ratoli' maps to LG7, and resistance from Georgian OSU 759.010 maps to LG2. DNA markers are used to select resistant seedlings in the greenhouse. Preliminary studies place resistance from Minnesota selection OSU 408.040 and 'Culpla' on LG6. Resistance from OSU 495.072 (Russia) and 'Crvenje' (Serbia) appears to be controlled by single loci, but they have not yet been mapped. Additional resistant genotypes of European hazelnut have been identified: seven selections from Moscow (Russia), 'Uebov' (Serbia), OSU 1187.101 (Holmskij, Russia), COR 187 (Finland), and 'Medium Long' (Geneva, NY). Selections from nuts collected in other countries have shown high resistance: two from southern Russia, three from Crimea (Ukraine), and two from the Republic of Georgia. The EFB resistance in C. americana 'Rush' and 'Winkler' and C. heterophylla 'Ogyoo' also appear to be controlled by single loci. Each year, controlled pollinations are made between resistant and good susceptible selections, and seedling populations scored for disease response in December. In his Ph.D. research, a graduate student developed new microsatellite markers and used them for fingerprinting and mapping. Four refereed journal articles were published from his thesis. The Ph.D. thesis research of another graduate student was on fine-mapping and map-based cloning of the EFB resistance gene from 'Gasaway'. Several publications have resulted from his thesis research. Our studies of EFB resistance and the breeding of resistant cultivars is recognized by our peers, resulting in invitations to present our findings at national and international meetings. The project was monitored by meetings, e-mail, and phone calls.