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Collaborative project: Development of resistant, homogeneous and productive varieties of Helleborus spec. – Subproject 2 (following project)
Project
Project code: 2814103506
Contract period: 01.06.2009
- 31.10.2010
Budget: 42,370 Euro
Purpose of research: Experimental development
The genus Helleborus comprises 22 species, which are allocated to six Helleborus sections. Helleborus species are distributed in different parts of Europe and East Asia. They show differences with regard to leaf and flower morphology, especially flower colour, and in susceptibility to hellebore leaf spot disease (Coniothyrium hellebori). Breeding programs aiming at these traits require the inclusion of a broader spectrum of Helleborus species in addition to the most popular species H. niger (Christmas Rose) and H. x hybridus (Lenten Rose) as fungicides are not always efficient against the disease and resistant genotypes cannot be developed from only one species of the Helleborus genus. To breed resistant genotypes interspecific crosses seemed to be most promising.
As a prerequisite for interspecific hybridisations, the Helleborus plant material was characterised cytologically, via flow cytometry and DNA fingerprinting. Cytological analyses revealed the same chromosome number of 2n=32 for all analysed Helleborus species. Nuclear DNA contents of Helleborus species were estimated via flow. Based on 1109 genome-wide distributed AFLP markers, genetic distances between species were calculated and a dendrogram was constructed to visualise genetic relationships. The phenogram reflected the taxonomic sub-division of the Helleborus genus into sections.
The main part of the project included the diallel crosses of genotypes of all species. This could be done over three different flowering periods.
As a next step, crossing barriers between Helleborus species were localised as predominantly postzygotic. Therefore, a techniques was established to overcome these barriers. Several hybrid offsprings were successfully obtained and a resistance against the fungus could be confirmed with a developed test as well.
The causal agent of the hellebore leaf spot disease was studied. A collection of 25 C.hellebori isolates was established from infected leaf material of different host species from various geographical locations. Their morphological characterisation by mycelial growth at different temperatures, conidial size and the induction of pycnidia revealed only marginal differences. All isolates were confirmed as causal agent of the disease by inoculation of H. niger plants. Using a molecular genetic approach based on RAPD markers, the genetic relationships were displayed in a phenogram.
As a broad spectrum of different genotypes from the different species was present a test to detect resistant or tolerant genotypes of the different species against C. hellebori was developed. Spores from the different locations were used and plants were infected and their resistance evaluated.
The interspecific Hybrids from this project are propagated in vitro and will be tested on the field/greenhouse in the flowering period 2011/2012 and/or 2012/2013. As an example the cross between H. niger and H. vesicarius is mentioned. This hybrid shows a resistance against C hellebore whereas one parent does not.
More interspecific Hybrids will be tested and the project was very successful to breed innovative and probably economic important varieties. These will be available in future and will enhance the range of existing varieties.
Section overview
Subjects
- Plant Breeding
- Horticulture
