Abstract
Hazelnut (Corylus avellana) is cultivated on 118 ha and ranks eighth in Slovenian fruit growing production, representing 2.8% of the total area of fruit plantations in the country. However, decline of some of the trees appeared in 2012 in two plantations located in eastern Slovenia. Together these orchards cover 5 ha, with around 1600 trees planted 12 to 15 years ago. By October 2018, ~12% of these trees had died, and an additional 12% showed decay symptoms. The dead and dying trees were scattered throughout both orchards, with no apparent pattern. The most affected cultivar was ‘Istrska dolgoplodna leska’. Using molecular diagnostic methods, we showed infection of symptomatic trees with three unrelated phytoplasmas: ‘Candidatus Phytoplasma fragariae’, of the 16SrXII-E phytoplasma subgroup, and phytoplasma of the 16SrV and 16SrIX groups. In 2018, the presence of ‘Ca. P. fragariae’ and/or phytoplasma of 16SrV group were confirmed in decayed hazelnut trees in eastern, north-eastern, central, south-eastern and western Slovenia. ‘Ca. P. fragariae’ has also been detected in a forest in south-western Slovenia, for Acer campestre, Carpinus betulus, Crataegus laevigata, Fraxinus ornus and Quercus petraea. All infected forest trees showed unusual dense proliferation of sprouts from roots and/or trunks. Molecular characterisations of partial 16S rRNA, secY, map and ribosomal protein genetic locus of hazelnut 16SrV phytoplasma isolates show that they are identical to isolates that can cause grapevine flavescence dorée disease. Here, the results of our recent study and the open questions on this burning issue for hazelnut production are presented.
Highlights
Corylus avellana L. (European hazelnut, or common hazelnut) is a monoecious and wind-pollinated broadleaf species
In two plantations located in Slovenska Bistrica that together cover 5 ha with around 1600 hazelnut trees planted 12 to 15 years ago, decline of some of the trees appeared in 2012
Phytoplasmas of the 16SrIX group have been detected in only one hazelnut tree, and up to now, no other plant species have been shown to be infected with phytoplasmas of this 16SrIX group in Slovenia
Summary
Corylus avellana L. (European hazelnut, or common hazelnut) is a monoecious and wind-pollinated broadleaf species. (European hazelnut, or common hazelnut) is a monoecious and wind-pollinated broadleaf species. It is typically a shrub, and is very common in naturally regenerated mixed-hardwood stands. It can be found throughout Europe, from Norway to the Iberian Peninsula, and East as far as the Urals. Hazelnut trees can be propagated both in generative (i.e., by seeds) and vegetative means. It is commonly propagated by vegetative means using shoot and root suckers and cuttings (Enescu et al 2016)
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