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

Abstract

<jats:p>The european hazelnut (<jats:italic>Corylus avellana</jats:italic> L.) is native 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 (2<jats:italic>n</jats:italic> = 2<jats:italic>x</jats:italic> = 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 and France. Studies of genetic diversity using simple sequence repeat 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 pollenizers 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 <jats:italic>S</jats:italic><jats:sub>2</jats:sub> in the Spanish-Italian group, <jats:italic>S</jats:italic><jats:sub>5</jats:sub> in the Central European group, <jats:italic>S</jats:italic><jats:sub>3</jats:sub> in the English group, and <jats:italic>S</jats:italic><jats:sub>4</jats:sub> in the Black Sea group. Most selections belonged to the Black Sea group, and <jats:italic>S</jats:italic><jats:sub>4</jats:sub> was by far the most common allele. Differences in allele frequency were also observed among seed lots within a country.</jats:p>

Assortment of Prospective Cultivars for Hazelnut Culture in Romania

“…In hazelnut, self-incompatibility is present and is of sporophytic type, being under the control of a single locus with multiple alleles. Until now, 33 S-alleles have been detected for different hazelnut cultivars (Mehlenbacher, 2014). In the case of Romanian cultivars such as 'Cozia', 'Uriaşe de Vâlcea', 'Arutela' and 'Primval', the S-alleles were not yet determined through the florescence microscope method.…”

Selection and Validation of Reference Genes for Quantitative RT-PCR Analysis in Corylus heterophylla Fisch. × Corylus avellana L.

“…According to world Corylus resources, world hazelnut species exhibit abundant characteristics, such as tree features, nut characteristics, stress resistance, and self-incompatibility, deserving more investigation and application. Hazelnut researchers are currently focusing on breeding for Eastern Filbert Blight resistance in European hazelnut [ 8 , 9 ], S-locus gene identification and distribution among cultivars and species [ 10 , 11 ], and cold-resistance breeding of interspecies hybrids with some wild species as the female parent [ 12 , 13 ]. As these studies progress, the use of molecular biotechnology is of great significance for the identification of trait-specific genes and molecular-assisted breeding in hazelnut.…”

Hazelnut Pollen Phenotyping Using Label-Free Impedance Flow Cytometry

“…Hazelnut ( Corylus avellana L.) is a diploid 2n = 2x = 22 ( Guo et al, 2009 ; Falistocco and Marconi, 2013 ), self-incompatible, monoecious species with peculiar reproductive biology, being wind-pollinated and flowering during late winter or early spring ( Germain, 1994 ). Its cross-pollination is enhanced by the sporophytic self-incompatibility occurring at the stigmatic surface, which is controlled by a single locus with multiple alleles ( Mehlenbacher, 2014 ). Fertilization is strongly delayed and pollen tubes wait dormant for weeks at the base of the style for ovules to be fully developed ( Liu et al, 2014 ).…”