1. Incompatibility in European Hazelnut
Meleksen Akin

2. Hazelnut (Corylus) Fagales order, Betulaceae family
8 shrub species and 5 tree species
European hazelnut (Corylus avellana L.) is most suited to cultivation and crop production

3. • Monoecious • Dichogamous • Wind pollinated
(Corylus avellana L.)
• Monoecious
• Dichogamous
• Wind pollinated

4. (Corylus avellana L.) Self-incompatible Cross-pollination enforced
Sporophytic incompatibility (rejection of self-pollen depends on the diploid genotype of the pollen controlled by a single locus with multiple alleles)

5. Sporophytic Incompatibility
Controlled by S-locus
Linkage group 5
33 alleles controlling self-incompatibility
Each allele is defined by a number

6. Sporophytic Incompatibility
Dominance or co-dominance in pollen
Co-dominance in stigmas
If the same allele is expressed by the stigma and the pollen, the cross is incompatible

7. Sporophytic Incompatibility
Example: ‘Lewis’ has S3S8
Female flowers express both of the alleles
Male flowers express one of the alleles
If the expressed allele by the pollen matches any of the alleles by the female flower, the cross is incompatible

8. Incompatibility Testing using Fluorescence Microscopy
Compatible • Excellent germination • Long parallel tubes
Incompatible
• Poor germination
• Short tubes, bulbs

9. Self-incompatibility
Very low nut sets
Blank nuts (shell without a nut)
Compatible pollinizer variety required

10. References S. A. Mehlenbacher
References S.A. Mehlenbacher. Geographic distribution of incompatibility alleles in cultivars and selections of European hazelnut. J Amer Soc Hort Sci –212 (2014). J. Olsen. Pollination and nut development. In: Growing hazelnuts in the Pacific Northwest. Oregon State University Extension Service Corvallis (2013). M.M. Thompson. Genetics of incompatibility in Corylus avellana L. Theor Appl Genet (1979).