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Geographic Distribution of Incompatibility Alleles in Cultivars and Selections of European Hazelnut

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Title Geographic Distribution of Incompatibility Alleles in Cultivars and Selections of European Hazelnut
Names Mehlenbacher, Shawn A. (creator)
Date Issued 2014-03 (iso8601)
Note This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Society for Horticultural Science and can be found at: http://journal.ashspublications.org/.
Abstract The european hazelnut (Corylus avellana L.) is native 24 to most of Europe and nearby
areas in Asia Minor and the Caucasus Mountains. Cross-pollination is enforced by sporophytic
incompatibility under the control of a single locus with multiple alleles (haplotypes).
Fluorescence microscopy is routinely used to determine if a pollination is compatible or
incompatible, and use of an array of known testers allows identification of the alleles of cultivars
and selections. Both alleles are expressed in the stigmas, but often only one is expressed in the
pollen because of dominance. Cultivars are highly heterozygous diploids (2n = 2x = 22) and
clonally propagated. Most of the world's leading cultivars were selected from local wild
populations near where they are now planted on a commercial scale. Genetic improvement
efforts are recent and, although tremendous genetic variability is available, such efforts have had
little impact outside of Oregon (USA) and France. Studies of genetic diversity using simple
sequence repeat (SSR) markers have placed most cultivars in one of the four main groups:
Spanish-Italian, Central European, English or Black Sea. This study presents 17 years of data on
incompatibility in hazelnut, including the discovery of six new S-alleles and determination of the
dominance relationships among 105 new pairs of alleles. The total number of alleles now stands
at 33. The S-alleles of 284 cultivars, 13 interspecific hybrids and 522 selections of diverse origin
are presented. The S-alleles identified in hazelnut cultivars is information that should be useful
to breeders in the planning of crosses, to curators of germplasm collections, and to growers and
nurseries as they choose cultivars and pollinizers when designing orchards. Differences in S-allele frequency seen in the cultivars and selections are related to geographic origin. The most
common alleles of cultivars in the major geographical groups are S₂ in the Spanish-Italian group,
S₅ in the Central European group, S₃ in the English group and S₄ in the Black Sea group. Most selections belonged to the Black Sea group, and S₄ was by far the most common allele.
Differences in allele frequency were also observed among seed lots within a country.
Genre Article
Topic Corylus avellana
Identifier Mehlenbacher, S. A. (2014). Geographic Distribution of Incompatibility Alleles in Cultivars and Selections of European Hazelnut. Journal of the American Society for Horticultural Science, 139(2), 191-212.

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