A number of temperate grasses and legumes, important for animal feeding, have their centre of diversity in the North-West European region, including perennial ryegrass (Lolium perenne L.; Engels raaigras), white clover (Trifolium repens L.; witte klaver) and Kentucky bluegrass (Poa pratensis L.; veldbeemdgras). These species traditionally occur in Dutch grasslands where they can be considered as typical. Undisturbed grasslands that are still in agricultural use have severely become reduced in number in the Netherlands. To investigate the need for conservation policies for such grasslands, diversity was assessed in perennial ryegrass, white clover and Kentucky bluegrass collected from traditional grasslands. This diversity was then compared with the diversity in commercial reference cultivars and in grasslands from nature reserves. Diversity estimation included morphological analyses and molecular characterization. The analyses indicated no substantial distinction between the gene pools of the three investigated groups for any of the three investigated species. In particular, comparison of traditional grasslands with grasslands from nature reserves indicated that basically these two groups covered the same range of genetic variation. It was therefore concluded that no specific in situ conservation measures are currently needed to maintain the genetic diversity of perennial ryegrass, white clover and Kentucky bluegrass occurring in traditional grasslands, considering that nature reserves are already under protective measures. Because perennial ryegrass, white clover and Kentucky bluegrass can be regarded key species of grasslands, the obtained results may be indicative of other species with similar life-history characteristics. Therefore, the need for specific conservation measures for traditional grasslands cannot be warranted

Treuren, R., van

Visser, L.

English

Wageningen Yield 

Centre for Genetic Resources, the Netherlands (CGN)
Policy Brief
Traditional grasslands
Conservation measures needed?
Rob van Treuren & Bert Visser
A number of temperate grasses and legumes, important for animal feeding, have their centre of diversity in the North-West European region,
including perennial ryegrass (Lolium perenne L.; Engels raaigras), white clover (Trifolium repens L.; witte klaver) and Kentucky bluegrass (Poa
pratensis L.; veldbeemdgras). These species traditionally occur in Dutch grasslands where they can be considered as typical.
Undisturbed grasslands that are still in agricultural use have severely become reduced in number in the Netherlands. To investigate the need for
conservation policies for such grasslands, diversity was assessed in perennial ryegrass, white clover and Kentucky bluegrass collected from
traditional grasslands. This diversity was then compared with the diversity in commercial reference cultivars and in grasslands from nature
reserves. Diversity estimation included morphological analyses and molecular characterization.
The analyses indicated no substantial distinction between the gene pools of the three investigated groups for any of the three investigated
species. In particular, comparison of traditional grasslands with grasslands from nature reserves indicated that basically these two groups
covered the same range of genetic variation. It was therefore concluded that no specific in situ conservation measures are currently needed to
maintain the genetic diversity of perennial ryegrass, white clover and Kentucky bluegrass occurring in traditional grasslands, considering that
nature reserves are already under protective measures.
Because perennial ryegrass, white clover and Kentucky bluegrass can be regarded key species of grasslands, the obtained results may be
indicative of other species with similar life-history characteristics. Therefore, the need for specific conservation measures for traditional
grasslands cannot be warranted.
Abstract
1. Background
According to one of the objectives of the Convention on Biodiversity
(CBD, 1992), member states have the responsibility to conserve the
biodiversity under their jurisdiction. To this aim, the CBD recognizes
ex situ and in situ strategies as complementary approaches. The
Netherlands is situated in the North-West European part of the
European-Siberian region of diversity, harboring only limited biodiversity
of cultivated crops in situ. However, a number of temperate grasses
and legumes, traditionally occurring in grasslands and important for
animal feeding, have their centre of diversity in this region, including
perennial ryegrass (Lolium perenne L.), white clover (Trifolium repens
L.) and Kentucky bluegrass (Poa pratensis L.). Whereas perennial
ryegrass and white clover are typical outcrossing species, Kentucky
bluegrass reproduces mainly through apomixis (i.e. seed production
without fertilization).
Optimization of fodder production during the last few decades may
have strongly reduced the biodiversity within temperate grasslands.
Original grassland vegetation has been replaced by more uniform
cultivars, adapted to the application of high doses of nitrogen fertilizer.
In cultivated grasslands clovers have largely disappeared because of
high nitrogen inputs. In the Netherlands, grasslands which have not
been resown over the last four decades and which received no, or only
small amounts, of nitrogen have become greatly reduced in number.
In 1998, an extensive farm survey by the Centre for Genetic
Resources, the Netherlands (CGN) revealed the location of only fifty of
such grasslands still in agricultural use; these were subsequently
designated “traditional grasslands” (Figure 1). Since then, the number
of traditional grasslands continued to decrease. Future survival of
traditional grasslands and hence any unique genetic diversity
contained in such systems can be considered unlikely.
Therefore, diversity in perennial ryegrass, white clover and Kentucky
bluegrass sampled from traditional grasslands was assessed, and
compared with the genetic diversity of cultivars that had a major
share in the cultivation of Dutch grasslands. In addition, a comparison
was made with the diversity of the species occurring in grasslands
from Dutch nature reserves. Aim of the study was to evaluate the
need for specific conservation policies for traditional grasslands.
Figure 1. Typical traditionally managed Dutch grassland with a mixture of grasses and clovers.
4 <> 5
According to the resident farmers of the identified traditional
grasslands, no resowing had occurred with commercial cultivars and
no high doses of nitrogen had been applied over the last 40 years.
From the group of 50 traditional grasslands, 16 were selected for the
present study, representing different soil types and geographic areas
(Figure 2).
In addition, reference cultivars of perennial ryegrass (8), white clover
(7) and Kentucky bluegrass (11) were included in the study in order to
enable comparison of the diversity observed within the traditional
grasslands with the diversity present in cultivars that together have
played an important role in Dutch grassland cultivation during the last
50 years.
Furthermore, the study included samples from seven Dutch nature
reserves in order to enable comparison with the genetic diversity of
grasslands that are already under conservation measures and
through which genetic diversity can be maintained in situ. Like the
traditional grasslands, the grasslands from the nature reserves were
managed extensively, and covered a similar geographic range (Figure
2). Up to 36 individuals of perennial ryegrass and white clover were
studied per grassland population and reference cultivar; for Kentucky
bluegrass up to 20 individuals were studied. All samples were
characterized by AFLP analysis, a state-of-the-art molecular marker
technology allowing detailed genetic comparisons at DNA level (Figure
3). Investigations of perennial ryegrass and white clover also included
morphological characterization in a field experiment (Figure 4).
2. Experimental design
Figure 2. Location of the investigated grasslands. Traditional grasslands are denoted
by ‘•’ and nature reserves by ‘*’.
Figure 3. Part of a molecular fingerprint of 24 perennial ryegrass plants (from left to
right), each sample consisting of a pattern of AFLP bands (from top to bottom).
Samples sharing a specific AFLP band indicate genetic similarity, whereas a difference
in band presence indicates genetic distinction.
3. Brief summary of the main results
For all three species, the AFLP data indicated higher levels of intra-
population diversity for the traditional grasslands than for the
reference cultivars. For perennial ryegrass and white clover this was
also observed for the morphological data. Compared to the traditional
grasslands, the reference cultivars of perennial ryegrass headed later,
whereas those of white clover were more vigorous. These results may
be explained as a result of the selection efforts of breeders.
When nature reserves were included in the analyses, it appeared that
the major part of the genetic variants observed in the group of
traditional grasslands were also found in the group of nature reserves,
which was most pronounced for perennial ryegrass and white clover
(Figure 5). For all three species, all common genetic variants
observed in traditional grasslands were detected in the group of
nature reserves as well. Sampling effects and the different number of
populations sampled per group are likely to account for the finding
that genetic variants observed in low frequency in traditional
grasslands appeared absent from nature reserves. Comparison of
traditional grasslands and nature reserves indicated that for the three
investigated species the two groups basically cover the same spectre
of genetic diversity.
Figure 4. Part of the experiment to assess morphological variation in white clover.
4. Policy implications
An accompanying study focusing on the socio-economic perspectives
of traditional grasslands indicated that their maintenance is highly
threatened in case the farm is sold or the owners are succeeded by
relatives (Janssens et al., 2002: Oude graslanden in Nederland:
verkenning naar motieven, bedrijfsvoering en perspectieven voor in
situ beheer. Rapport 3.02.04. LEI, Den Haag). This was confirmed by
the present study since between 2000 and 2005, 4 out of the 16
investigated traditional grasslands were given another destination by
the new owners. Without conservation measures, traditional
grasslands will probably disappear in the long run considering their
continuing decrease in number. Hence, the question was whether a
comprehensive diversity study in the three key species of grasslands
could provide justification for the development of conservation
measures.
It has been suggested that conservation efforts should foremost
focus on genetic variants that are typical of specific populations
adapted to particular agro-ecosystems. However, it appeared that
traditional grasslands and grasslands from nature reserves basically
cover the same spectre of genetic variation. Because the grasslands
located in nature reserves are already under protective measures, no
specific in situ conservation measures are currently justified to
maintain the genetic diversity of perennial ryegrass, white clover and
Kentucky bluegrass occurring in traditional grasslands.
It can be questioned whether the results obtained for perennial
ryegrass, white clover and Kentucky bluegrass also apply to other
species, in particular species that can be expected to exhibit high
levels of genetic differentiation. However, this is considered rather
unlikely because reproductive behaviour is a key factor influencing
population differentiation and because the three investigated species
differ considerably in that respect.
In this context, it should be noted that in the present study only
genetic diversity within species was addressed, whereas
conservationists may consider other aspects of biodiversity, such as
species diversity, focussing on rare species for which traditional
grasslands may form a refuge. The fact that soil types, management
practices, acreages, and geographic distribution of traditional
grasslands and nature reserves converge, suggests that such
species are likely to have an equal survival probability in nature
reserves as in traditional grasslands. These considerations lead to the
conclusion that specific measures to maintain traditional grasslands
can neither be warranted for conservation of within-species diversity
nor for conservation of between-species diversity.
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Figure 5.  Number of genetic variants observed for the three species studied in the group of traditional grasslands, together with the number of these genetic variants also
detected in the group of reference cultivars and nature reserves.
This project was carried out within the framework of the programs Agrobiodiversity and Genetic Resources, financed by the Netherlands Ministry
of Agriculture, Nature and Food Quality. The authors gratefully acknowledge the kind co-operation of the managers and owners of the study
sites, without whom the project would have been impossible. For their involvement in the project, the authors would also like to thank Loek van
Soest, Noor Bas, Harm Dijkstra, Theo van Hintum, Peter Goossens, Hans Jansen, Chris Kik, Dick Klein-Geltink, Rob Geerts, Wendy van’t
Westende, Hanneke van der Schoot, Twan Moers, Eddy Ydema, Dirk Visser and Jannie Tellinga. The project results for perennial ryegrass and
white clover are described in more detail in Molecular Ecology (2005, 14: 39-52). Details of the study in Kentucky bluegrass will be presented in a
forthcoming paper.
Acknowledgements
Colophon
The Centre for Genetic Resources, the Netherlands (CGN) conducts, on behalf of the Dutch government, statutory research tasks associated
with the genetic diversity and identity of species that are important for agriculture and forestry. CGN is an independent research unit within DLO
Foundation that assists the government in its statutory tasks. Its activities are aimed at the ex situ conservation, support for in situ
conservation, and promotion of the use of genetic propagation material in support of breeding and research, and as part of our bio-cultural
heritage. Policy support of the Dutch government and international organizations is provided as a complementary activity. The programme
concerns crops and forest species as well as domestic animals.
Information
Website: www.cgn.wur.nl
Postal address: Centre for Genetic Resources, the Netherlands (CGN)
P.O. Box 16, 6700 AA Wageningen, the Netherlands
Visiting address: Centre for Genetic Resources, the Netherlands (CGN)
Plant Research International, location Born-Zuid (building 122)
Bornsesteeg 65, 6708 PD Wageningen, the Netherlands
Phone: +31 317 477045
Fax: +31 317 423110
E-mail: cgn@wur.nl
Centre for Genetic Resources, the Netherlands (CGN)
Policy Brief
Traditional grasslands
Conservation measures needed?
Rob van Treuren & Bert Visser


Traditional grasslands : Conservation measures needed?

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